Merge branch 'master' into clang-analyzer

127 files changed, 272 insertions, 327 deletions

diff --git a/src/lib/asn1/alg_id.cpp b/src/lib/asn1/alg_id.cpp
index 7d476a225..75ea78c18 100644
--- a/src/lib/asn1/alg_id.cpp
+++ b/src/lib/asn1/alg_id.cpp
@@ -16,32 +16,24 @@ namespace Botan {
 * Create an AlgorithmIdentifier
 */
 AlgorithmIdentifier::AlgorithmIdentifier(const OID& alg_id,
-                                         const std::vector<byte>& param)
-   {
-   oid = alg_id;
-   parameters = param;
-   }
+                                         const std::vector<byte>& param) : oid(alg_id), parameters(param)
+   {}
 
 /*
 * Create an AlgorithmIdentifier
 */
 AlgorithmIdentifier::AlgorithmIdentifier(const std::string& alg_id,
-                                         const std::vector<byte>& param)
-   {
-   oid = OIDS::lookup(alg_id);
-   parameters = param;
-   }
+                                         const std::vector<byte>& param) : oid(OIDS::lookup(alg_id)), parameters(param)
+   {}
 
 /*
 * Create an AlgorithmIdentifier
 */
 AlgorithmIdentifier::AlgorithmIdentifier(const OID& alg_id,
-                                         Encoding_Option option)
+                                         Encoding_Option option) : oid(alg_id), parameters()
    {
    const byte DER_NULL[] = { 0x05, 0x00 };
 
-   oid = alg_id;
-
    if(option == USE_NULL_PARAM)
       parameters += std::pair<const byte*, size_t>(DER_NULL, sizeof(DER_NULL));
    }
@@ -50,12 +42,10 @@ AlgorithmIdentifier::AlgorithmIdentifier(const OID& alg_id,
 * Create an AlgorithmIdentifier
 */
 AlgorithmIdentifier::AlgorithmIdentifier(const std::string& alg_id,
-                                         Encoding_Option option)
+                                         Encoding_Option option) : oid(OIDS::lookup(alg_id)), parameters()
    {
    const byte DER_NULL[] = { 0x05, 0x00 };
 
-   oid = OIDS::lookup(alg_id);
-
    if(option == USE_NULL_PARAM)
       parameters += std::pair<const byte*, size_t>(DER_NULL, sizeof(DER_NULL));
    }
diff --git a/src/lib/asn1/asn1_attribute.cpp b/src/lib/asn1/asn1_attribute.cpp
index 406a57d9a..bd7e5bf11 100644
--- a/src/lib/asn1/asn1_attribute.cpp
+++ b/src/lib/asn1/asn1_attribute.cpp
@@ -15,21 +15,15 @@ namespace Botan {
 /*
 * Create an Attribute
 */
-Attribute::Attribute(const OID& attr_oid, const std::vector<byte>& attr_value)
-   {
-   oid = attr_oid;
-   parameters = attr_value;
-   }
+Attribute::Attribute(const OID& attr_oid, const std::vector<byte>& attr_value) : oid(attr_oid), parameters(attr_value)
+   {}
 
 /*
 * Create an Attribute
 */
 Attribute::Attribute(const std::string& attr_oid,
-                     const std::vector<byte>& attr_value)
-   {
-   oid = OIDS::lookup(attr_oid);
-   parameters = attr_value;
-   }
+                     const std::vector<byte>& attr_value) : oid(OIDS::lookup(attr_oid)), parameters(attr_value)
+   {}
 
 /*
 * DER encode a Attribute
diff --git a/src/lib/asn1/asn1_obj.h b/src/lib/asn1/asn1_obj.h
index 2bd2b1ed5..3e119dc01 100644
--- a/src/lib/asn1/asn1_obj.h
+++ b/src/lib/asn1/asn1_obj.h
@@ -114,7 +114,7 @@ bool maybe_BER(DataSource& src);
 */
 struct BOTAN_DLL BER_Decoding_Error : public Decoding_Error
    {
-   BER_Decoding_Error(const std::string&);
+   explicit BER_Decoding_Error(const std::string&);
    };
 
 /**
diff --git a/src/lib/asn1/asn1_str.cpp b/src/lib/asn1/asn1_str.cpp
index 809448888..c378d5dfe 100644
--- a/src/lib/asn1/asn1_str.cpp
+++ b/src/lib/asn1/asn1_str.cpp
@@ -62,9 +62,8 @@ ASN1_Tag choose_encoding(const std::string& str,
 /*
 * Create an ASN1_String
 */
-ASN1_String::ASN1_String(const std::string& str, ASN1_Tag t) : m_tag(t)
+ASN1_String::ASN1_String(const std::string& str, ASN1_Tag t) : m_iso_8859_str(Charset::transcode(str, LOCAL_CHARSET, LATIN1_CHARSET)), m_tag(t)
    {
-   m_iso_8859_str = Charset::transcode(str, LOCAL_CHARSET, LATIN1_CHARSET);
 
    if(m_tag == DIRECTORY_STRING)
       m_tag = choose_encoding(m_iso_8859_str, "latin1");
@@ -83,11 +82,8 @@ ASN1_String::ASN1_String(const std::string& str, ASN1_Tag t) : m_tag(t)
 /*
 * Create an ASN1_String
 */
-ASN1_String::ASN1_String(const std::string& str)
-   {
-   m_iso_8859_str = Charset::transcode(str, LOCAL_CHARSET, LATIN1_CHARSET);
-   m_tag = choose_encoding(m_iso_8859_str, "latin1");
-   }
+ASN1_String::ASN1_String(const std::string& str) : m_iso_8859_str(Charset::transcode(str, LOCAL_CHARSET, LATIN1_CHARSET)), m_tag(choose_encoding(m_iso_8859_str, "latin1"))
+   {}
 
 /*
 * Return this string in ISO 8859-1 encoding
@@ -141,7 +137,7 @@ void ASN1_String::decode_from(BER_Decoder& source)
       charset_is = LATIN1_CHARSET;
 
    *this = ASN1_String(
-      Charset::transcode(ASN1::to_string(obj), charset_is, LOCAL_CHARSET),
+      Charset::transcode(ASN1::to_string(obj), LOCAL_CHARSET, charset_is),
       obj.type_tag);
    }
 
diff --git a/src/lib/asn1/asn1_str.h b/src/lib/asn1/asn1_str.h
index 269b821b8..1d75ec519 100644
--- a/src/lib/asn1/asn1_str.h
+++ b/src/lib/asn1/asn1_str.h
@@ -26,7 +26,7 @@ class BOTAN_DLL ASN1_String final : public ASN1_Object
 
       ASN1_Tag tagging() const;
 
-      ASN1_String(const std::string& = "");
+      explicit ASN1_String(const std::string& = "");
       ASN1_String(const std::string&, ASN1_Tag);
    private:
       std::string m_iso_8859_str;
diff --git a/src/lib/asn1/asn1_time.h b/src/lib/asn1/asn1_time.h
index 269cc7983..ba5b84838 100644
--- a/src/lib/asn1/asn1_time.h
+++ b/src/lib/asn1/asn1_time.h
@@ -41,7 +41,7 @@ class BOTAN_DLL X509_Time final : public ASN1_Object
       X509_Time() {}
 
       /// Create a X509_Time from a time point
-      X509_Time(const std::chrono::system_clock::time_point& time);
+      explicit X509_Time(const std::chrono::system_clock::time_point& time);
 
       /// Create an X509_Time from string
       X509_Time(const std::string& t_spec, ASN1_Tag tag);
diff --git a/src/lib/asn1/ber_dec.h b/src/lib/asn1/ber_dec.h
index b755251c5..8a5c9ca45 100644
--- a/src/lib/asn1/ber_dec.h
+++ b/src/lib/asn1/ber_dec.h
@@ -157,13 +157,13 @@ class BOTAN_DLL BER_Decoder
 
       BER_Decoder& operator=(const BER_Decoder&) = delete;
 
-      BER_Decoder(DataSource&);
+      explicit BER_Decoder(DataSource&);
 
       BER_Decoder(const byte[], size_t);
 
-      BER_Decoder(const secure_vector<byte>&);
+      explicit BER_Decoder(const secure_vector<byte>&);
 
-      BER_Decoder(const std::vector<byte>& vec);
+      explicit BER_Decoder(const std::vector<byte>& vec);
 
       BER_Decoder(const BER_Decoder&);
       ~BER_Decoder();
diff --git a/src/lib/asn1/oid_lookup/oids.cpp b/src/lib/asn1/oid_lookup/oids.cpp
index 0d1ab58ff..cdb863494 100644
--- a/src/lib/asn1/oid_lookup/oids.cpp
+++ b/src/lib/asn1/oid_lookup/oids.cpp
@@ -125,8 +125,8 @@ void OID_Map::read_cfg(std::istream& cfg, const std::string& source)
       const std::string oid = clean_ws(s.substr(0, eq));
       const std::string name = clean_ws(s.substr(eq + 1, std::string::npos));
 
-      m_str2oid.insert(std::make_pair(name, oid));
-      m_oid2str.insert(std::make_pair(oid, name));
+      m_str2oid.insert(std::make_pair(name, OID(oid)));
+      m_oid2str.insert(std::make_pair(OID(oid), name));
       }
    }
 
diff --git a/src/lib/asn1/x509_dn.h b/src/lib/asn1/x509_dn.h
index a86cc6417..12553a1a0 100644
--- a/src/lib/asn1/x509_dn.h
+++ b/src/lib/asn1/x509_dn.h
@@ -38,8 +38,8 @@ class BOTAN_DLL X509_DN final : public ASN1_Object
       std::vector<byte> get_bits() const;
 
       X509_DN();
-      X509_DN(const std::multimap<OID, std::string>&);
-      X509_DN(const std::multimap<std::string, std::string>&);
+      explicit X509_DN(const std::multimap<OID, std::string>&);
+      explicit X509_DN(const std::multimap<std::string, std::string>&);
    private:
       std::multimap<OID, ASN1_String> m_dn_info;
       std::vector<byte> m_dn_bits;
diff --git a/src/lib/base/algo_registry.h b/src/lib/base/algo_registry.h
index eebbaa4e8..ebc23bfca 100644
--- a/src/lib/base/algo_registry.h
+++ b/src/lib/base/algo_registry.h
@@ -11,6 +11,7 @@
 #include <botan/build.h>
 #include <botan/types.h>
 #include <botan/exceptn.h>
+#include <botan/scan_name.h>
 #include <functional>
 #include <mutex>
 #include <vector>
@@ -212,7 +213,7 @@ class Algo_Registry
    };
 
 template<typename T> T*
-make_a(const typename T::Spec& spec, const std::string provider = "")
+make_a(const typename T::Spec& spec, const std::string& provider = "")
    {
    return Algo_Registry<T>::global_registry().make(spec, provider);
    }
@@ -257,7 +258,7 @@ make_new_T_1str_req(const typename Algo_Registry<T>::Spec& spec)
 template<typename T, typename X> T*
 make_new_T_1X(const typename Algo_Registry<T>::Spec& spec)
    {
-   std::unique_ptr<X> x(Algo_Registry<X>::global_registry().make(spec.arg(0)));
+   std::unique_ptr<X> x(Algo_Registry<X>::global_registry().make(Botan::SCAN_Name(spec.arg(0))));
    if(!x)
       throw Exception(spec.arg(0));
    return new T(x.release());
diff --git a/src/lib/base/init.h b/src/lib/base/init.h
index 0c61eba6f..7709883af 100644
--- a/src/lib/base/init.h
+++ b/src/lib/base/init.h
@@ -22,7 +22,7 @@ namespace Botan {
 class BOTAN_DLL LibraryInitializer
    {
    public:
-      LibraryInitializer(const std::string& s = "") { initialize(s); }
+      explicit LibraryInitializer(const std::string& s = "") { initialize(s); }
       ~LibraryInitializer() { deinitialize(); }
 
       static void initialize(const std::string& = "");
diff --git a/src/lib/base/key_spec.h b/src/lib/base/key_spec.h
index f9cdcc78d..82e0e7e6f 100644
--- a/src/lib/base/key_spec.h
+++ b/src/lib/base/key_spec.h
@@ -22,7 +22,7 @@ class BOTAN_DLL Key_Length_Specification
       * Constructor for fixed length keys
       * @param keylen the supported key length
       */
-      Key_Length_Specification(size_t keylen) :
+      explicit Key_Length_Specification(size_t keylen) :
          m_min_keylen(keylen),
          m_max_keylen(keylen),
          m_keylen_mod(1)
diff --git a/src/lib/base/scan_name.cpp b/src/lib/base/scan_name.cpp
index 4688d0871..08f5e8702 100644
--- a/src/lib/base/scan_name.cpp
+++ b/src/lib/base/scan_name.cpp
@@ -70,10 +70,8 @@ SCAN_Name::SCAN_Name(const char* algo_spec) : SCAN_Name(std::string(algo_spec))
    {
    }
 
-SCAN_Name::SCAN_Name(std::string algo_spec)
+SCAN_Name::SCAN_Name(std::string algo_spec) : m_orig_algo_spec(algo_spec), m_alg_name(), m_args(), m_mode_info()
    {
-   m_orig_algo_spec = algo_spec;
-
    std::vector<std::pair<size_t, std::string> > name;
    size_t level = 0;
    std::pair<size_t, std::string> accum = std::make_pair(level, "");
diff --git a/src/lib/base/scan_name.h b/src/lib/base/scan_name.h
index 43441e19c..d59d5889e 100644
--- a/src/lib/base/scan_name.h
+++ b/src/lib/base/scan_name.h
@@ -26,12 +26,12 @@ class BOTAN_DLL SCAN_Name
       /**
       * @param algo_spec A SCAN-format name
       */
-      SCAN_Name(const char* algo_spec);
+      explicit SCAN_Name(const char* algo_spec);
 
       /**
       * @param algo_spec A SCAN-format name
       */
-      SCAN_Name(std::string algo_spec);
+      explicit SCAN_Name(std::string algo_spec);
 
       /**
       * @param algo_spec A SCAN-format name
diff --git a/src/lib/base/symkey.h b/src/lib/base/symkey.h
index 3b0208e51..c780e5239 100644
--- a/src/lib/base/symkey.h
+++ b/src/lib/base/symkey.h
@@ -61,7 +61,7 @@ class BOTAN_DLL OctetString
       * Create a new OctetString
       * @param str is a hex encoded string
       */
-      OctetString(const std::string& str = "");
+      explicit OctetString(const std::string& str = "");
 
       /**
       * Create a new random OctetString
diff --git a/src/lib/block/block_cipher.cpp b/src/lib/block/block_cipher.cpp
index 7b52f8716..c70ba229d 100644
--- a/src/lib/block/block_cipher.cpp
+++ b/src/lib/block/block_cipher.cpp
@@ -150,7 +150,7 @@ BlockCipher::~BlockCipher() {}
 std::unique_ptr<BlockCipher> BlockCipher::create(const std::string& algo_spec,
                                                  const std::string& provider)
    {
-   return std::unique_ptr<BlockCipher>(make_a<BlockCipher>(algo_spec, provider));
+   return std::unique_ptr<BlockCipher>(make_a<BlockCipher>(Botan::BlockCipher::Spec(algo_spec), provider));
    }
 
 std::vector<std::string> BlockCipher::providers(const std::string& algo_spec)
diff --git a/src/lib/block/cast/cast128.cpp b/src/lib/block/cast/cast128.cpp
index ce9e86794..53f7d4611 100644
--- a/src/lib/block/cast/cast128.cpp
+++ b/src/lib/block/cast/cast128.cpp
@@ -330,7 +330,7 @@ void CAST_128::cast_ks(secure_vector<u32bit>& K,
       {
       public:
          byte operator()(size_t i) { return (m_X[i/4] >> (8*(3 - (i%4)))); }
-         ByteReader(const u32bit* x) : m_X(x) {}
+         explicit ByteReader(const u32bit* x) : m_X(x) {}
       private:
          const u32bit* m_X;
       };
diff --git a/src/lib/block/gost_28147/gost_28147.h b/src/lib/block/gost_28147/gost_28147.h
index 11f5228a6..4105154e3 100644
--- a/src/lib/block/gost_28147/gost_28147.h
+++ b/src/lib/block/gost_28147/gost_28147.h
@@ -63,9 +63,9 @@ class BOTAN_DLL GOST_28147_89 final : public Block_Cipher_Fixed_Params<8, 32>
       /**
       * @param params the sbox parameters to use
       */
-      GOST_28147_89(const GOST_28147_89_Params& params);
+      explicit GOST_28147_89(const GOST_28147_89_Params& params);
    private:
-      GOST_28147_89(const std::vector<u32bit>& other_SBOX) :
+      explicit GOST_28147_89(const std::vector<u32bit>& other_SBOX) :
          m_SBOX(other_SBOX), m_EK(8) {}
 
       void key_schedule(const byte[], size_t) override;
diff --git a/src/lib/block/rc5/rc5.h b/src/lib/block/rc5/rc5.h
index 17469205f..4d9232326 100644
--- a/src/lib/block/rc5/rc5.h
+++ b/src/lib/block/rc5/rc5.h
@@ -29,7 +29,7 @@ class BOTAN_DLL RC5 final : public Block_Cipher_Fixed_Params<8, 1, 32>
       * @param rounds the number of RC5 rounds to run. Must be between
       * 8 and 32 and a multiple of 4.
       */
-      RC5(size_t rounds);
+      explicit RC5(size_t rounds);
    private:
       void key_schedule(const byte[], size_t) override;
 
diff --git a/src/lib/block/safer/safer_sk.h b/src/lib/block/safer/safer_sk.h
index babc22eb9..af944b36c 100644
--- a/src/lib/block/safer/safer_sk.h
+++ b/src/lib/block/safer/safer_sk.h
@@ -29,7 +29,7 @@ class BOTAN_DLL SAFER_SK final : public Block_Cipher_Fixed_Params<8, 16>
       * @param rounds the number of rounds to use - must be between 1
       * and 13
       */
-      SAFER_SK(size_t rounds);
+      explicit SAFER_SK(size_t rounds);
    private:
       void key_schedule(const byte[], size_t) override;
 
diff --git a/src/lib/cert/cvc/asn1_eac_str.cpp b/src/lib/cert/cvc/asn1_eac_str.cpp
index 0134399d8..26bc7f09d 100644
--- a/src/lib/cert/cvc/asn1_eac_str.cpp
+++ b/src/lib/cert/cvc/asn1_eac_str.cpp
@@ -85,7 +85,7 @@ void ASN1_EAC_String::decode_from(BER_Decoder& source)
    try
       {
       *this = ASN1_EAC_String(
-         Charset::transcode(ASN1::to_string(obj), charset_is, LOCAL_CHARSET),
+         Charset::transcode(ASN1::to_string(obj), LOCAL_CHARSET, chaset_is),
          obj.type_tag);
       }
    catch(Invalid_Argument& inv_arg)
diff --git a/src/lib/cert/x509/certstor.h b/src/lib/cert/x509/certstor.h
index eb42c6a49..29948c709 100644
--- a/src/lib/cert/x509/certstor.h
+++ b/src/lib/cert/x509/certstor.h
@@ -48,9 +48,9 @@ class BOTAN_DLL Certificate_Store_In_Memory : public Certificate_Store
       * Attempt to parse all files in dir (including subdirectories)
       * as certificates. Ignores errors.
       */
-      Certificate_Store_In_Memory(const std::string& dir);
+      explicit Certificate_Store_In_Memory(const std::string& dir);
 
-      Certificate_Store_In_Memory(const X509_Certificate& cert);
+      explicit Certificate_Store_In_Memory(const X509_Certificate& cert);
 
       Certificate_Store_In_Memory() {}
 
@@ -74,7 +74,7 @@ class BOTAN_DLL Certificate_Store_In_Memory : public Certificate_Store
 class BOTAN_DLL Certificate_Store_Overlay : public Certificate_Store
    {
    public:
-      Certificate_Store_Overlay(const std::vector<X509_Certificate>& certs) :
+      explicit Certificate_Store_Overlay(const std::vector<X509_Certificate>& certs) :
          m_certs(certs) {}
 
       std::vector<X509_DN> all_subjects() const override;
diff --git a/src/lib/cert/x509/crl_ent.h b/src/lib/cert/x509/crl_ent.h
index ceefdb191..11ab34365 100644
--- a/src/lib/cert/x509/crl_ent.h
+++ b/src/lib/cert/x509/crl_ent.h
@@ -63,7 +63,7 @@ class BOTAN_DLL CRL_Entry final : public ASN1_Object
       /**
       * Construct an empty CRL entry.
       */
-      CRL_Entry(bool throw_on_unknown_critical_extension = false);
+      explicit CRL_Entry(bool throw_on_unknown_critical_extension = false);
 
       /**
       * Construct an CRL entry.
diff --git a/src/lib/cert/x509/pkcs10.h b/src/lib/cert/x509/pkcs10.h
index 94db222cd..8c9f49d84 100644
--- a/src/lib/cert/x509/pkcs10.h
+++ b/src/lib/cert/x509/pkcs10.h
@@ -84,20 +84,20 @@ class BOTAN_DLL PKCS10_Request final : public X509_Object
       * Create a PKCS#10 Request from a data source.
       * @param source the data source providing the DER encoded request
       */
-      PKCS10_Request(DataSource& source);
+      explicit PKCS10_Request(DataSource& source);
 
       /**
       * Create a PKCS#10 Request from a file.
       * @param filename the name of the file containing the DER or PEM
       * encoded request file
       */
-      PKCS10_Request(const std::string& filename);
+      explicit PKCS10_Request(const std::string& filename);
 
       /**
       * Create a PKCS#10 Request from binary data.
       * @param vec a std::vector containing the DER value
       */
-      PKCS10_Request(const std::vector<byte>& vec);
+      explicit PKCS10_Request(const std::vector<byte>& vec);
    private:
       void force_decode() override;
       void handle_attribute(const Attribute&);
diff --git a/src/lib/cert/x509/x509_crl.h b/src/lib/cert/x509/x509_crl.h
index 25556000d..29057e944 100644
--- a/src/lib/cert/x509/x509_crl.h
+++ b/src/lib/cert/x509/x509_crl.h
@@ -27,7 +27,7 @@ class BOTAN_DLL X509_CRL final : public X509_Object
       */
       struct BOTAN_DLL X509_CRL_Error : public Exception
          {
-         X509_CRL_Error(const std::string& error) :
+         explicit X509_CRL_Error(const std::string& error) :
             Exception("X509_CRL: " + error) {}
          };
 
diff --git a/src/lib/cert/x509/x509_ext.cpp b/src/lib/cert/x509/x509_ext.cpp
index b4b918529..7dd4a3190 100644
--- a/src/lib/cert/x509/x509_ext.cpp
+++ b/src/lib/cert/x509/x509_ext.cpp
@@ -309,11 +309,8 @@ void Subject_Key_ID::contents_to(Data_Store& subject, Data_Store&) const
 /*
 * Subject_Key_ID Constructor
 */
-Subject_Key_ID::Subject_Key_ID(const std::vector<byte>& pub_key)
-   {
-   SHA_160 hash;
-   m_key_id = unlock(hash.process(pub_key));
-   }
+Subject_Key_ID::Subject_Key_ID(const std::vector<byte>& pub_key) : m_key_id(unlock(SHA_160().process(pub_key)))
+   {}
 
 /*
 * Encode the extension
@@ -384,11 +381,8 @@ void Alternative_Name::contents_to(Data_Store& subject_info,
 * Alternative_Name Constructor
 */
 Alternative_Name::Alternative_Name(const AlternativeName& alt_name,
-                                   const std::string& oid_name_str)
-   {
-   this->m_alt_name = alt_name;
-   this->m_oid_name_str = oid_name_str;
-   }
+                                   const std::string& oid_name_str) : m_alt_name(alt_name), m_oid_name_str(oid_name_str)
+   {}
 
 /*
 * Subject_Alternative_Name Constructor
@@ -448,7 +442,7 @@ class Policy_Information : public ASN1_Object
       OID oid;
 
       Policy_Information() {}
-      Policy_Information(const OID& oid_) : oid(oid_) {}
+      explicit Policy_Information(const OID& oid) : oid(oid) {}
 
       void encode_into(DER_Encoder& codec) const override
          {
@@ -476,7 +470,7 @@ std::vector<byte> Certificate_Policies::encode_inner() const
    std::vector<Policy_Information> policies;
 
    for(size_t i = 0; i != m_oids.size(); ++i)
-      policies.push_back(m_oids[i]);
+      policies.push_back(Policy_Information(m_oids[i]));
 
    return DER_Encoder()
       .start_cons(SEQUENCE)
diff --git a/src/lib/cert/x509/x509_ext.h b/src/lib/cert/x509/x509_ext.h
index e9e718014..0614b9a52 100644
--- a/src/lib/cert/x509/x509_ext.h
+++ b/src/lib/cert/x509/x509_ext.h
@@ -70,7 +70,7 @@ class BOTAN_DLL Extensions : public ASN1_Object
       Extensions& operator=(const Extensions&);
 
       Extensions(const Extensions&);
-      Extensions(bool st = true) : m_throw_on_unknown_critical(st) {}
+      explicit Extensions(bool st = true) : m_throw_on_unknown_critical(st) {}
       ~Extensions();
    private:
       static Certificate_Extension* get_extension(const OID&);
@@ -117,7 +117,7 @@ class BOTAN_DLL Key_Usage final : public Certificate_Extension
    public:
       Key_Usage* copy() const override { return new Key_Usage(m_constraints); }
 
-      Key_Usage(Key_Constraints c = NO_CONSTRAINTS) : m_constraints(c) {}
+      explicit Key_Usage(Key_Constraints c = NO_CONSTRAINTS) : m_constraints(c) {}
 
       Key_Constraints get_constraints() const { return m_constraints; }
    private:
@@ -142,7 +142,7 @@ class BOTAN_DLL Subject_Key_ID final : public Certificate_Extension
          { return new Subject_Key_ID(m_key_id); }
 
       Subject_Key_ID() {}
-      Subject_Key_ID(const std::vector<byte>&);
+      explicit Subject_Key_ID(const std::vector<byte>&);
 
       std::vector<byte> get_key_id() const { return m_key_id; }
    private:
@@ -167,7 +167,7 @@ class BOTAN_DLL Authority_Key_ID final : public Certificate_Extension
          { return new Authority_Key_ID(m_key_id); }
 
       Authority_Key_ID() {}
-      Authority_Key_ID(const std::vector<byte>& k) : m_key_id(k) {}
+      explicit Authority_Key_ID(const std::vector<byte>& k) : m_key_id(k) {}
 
       std::vector<byte> get_key_id() const { return m_key_id; }
    private:
@@ -215,7 +215,7 @@ class BOTAN_DLL Subject_Alternative_Name : public Alternative_Name
       Subject_Alternative_Name* copy() const override
          { return new Subject_Alternative_Name(get_alt_name()); }
 
-      Subject_Alternative_Name(const AlternativeName& = AlternativeName());
+      explicit Subject_Alternative_Name(const AlternativeName& = AlternativeName());
    };
 
 /**
@@ -227,7 +227,7 @@ class BOTAN_DLL Issuer_Alternative_Name : public Alternative_Name
       Issuer_Alternative_Name* copy() const override
          { return new Issuer_Alternative_Name(get_alt_name()); }
 
-      Issuer_Alternative_Name(const AlternativeName& = AlternativeName());
+      explicit Issuer_Alternative_Name(const AlternativeName& = AlternativeName());
    };
 
 /**
@@ -240,7 +240,7 @@ class BOTAN_DLL Extended_Key_Usage final : public Certificate_Extension
          { return new Extended_Key_Usage(m_oids); }
 
       Extended_Key_Usage() {}
-      Extended_Key_Usage(const std::vector<OID>& o) : m_oids(o) {}
+      explicit Extended_Key_Usage(const std::vector<OID>& o) : m_oids(o) {}
 
       std::vector<OID> get_oids() const { return m_oids; }
    private:
@@ -265,7 +265,7 @@ class BOTAN_DLL Certificate_Policies final : public Certificate_Extension
          { return new Certificate_Policies(m_oids); }
 
       Certificate_Policies() {}
-      Certificate_Policies(const std::vector<OID>& o) : m_oids(o) {}
+      explicit Certificate_Policies(const std::vector<OID>& o) : m_oids(o) {}
 
       std::vector<OID> get_oids() const { return m_oids; }
    private:
@@ -288,7 +288,7 @@ class BOTAN_DLL Authority_Information_Access final : public Certificate_Extensio
 
       Authority_Information_Access() {}
 
-      Authority_Information_Access(const std::string& ocsp) :
+      explicit Authority_Information_Access(const std::string& ocsp) :
          m_ocsp_responder(ocsp) {}
 
    private:
@@ -338,7 +338,7 @@ class BOTAN_DLL CRL_ReasonCode final : public Certificate_Extension
       CRL_ReasonCode* copy() const override
          { return new CRL_ReasonCode(m_reason); }
 
-      CRL_ReasonCode(CRL_Code r = UNSPECIFIED) : m_reason(r) {}
+      explicit CRL_ReasonCode(CRL_Code r = UNSPECIFIED) : m_reason(r) {}
 
       CRL_Code get_reason() const { return m_reason; }
    private:
@@ -374,7 +374,7 @@ class BOTAN_DLL CRL_Distribution_Points final : public Certificate_Extension
 
       CRL_Distribution_Points() {}
 
-      CRL_Distribution_Points(const std::vector<Distribution_Point>& points) :
+      explicit CRL_Distribution_Points(const std::vector<Distribution_Point>& points) :
          m_distribution_points(points) {}
 
       std::vector<Distribution_Point> distribution_points() const
diff --git a/src/lib/cert/x509/x509cert.h b/src/lib/cert/x509/x509cert.h
index d5784f427..0329fde47 100644
--- a/src/lib/cert/x509/x509cert.h
+++ b/src/lib/cert/x509/x509cert.h
@@ -220,16 +220,16 @@ class BOTAN_DLL X509_Certificate final : public X509_Object
       * PEM encoded certificate.
       * @param source the data source
       */
-      X509_Certificate(DataSource& source);
+      explicit X509_Certificate(DataSource& source);
 
       /**
       * Create a certificate from a file containing the DER or PEM
       * encoded certificate.
       * @param filename the name of the certificate file
       */
-      X509_Certificate(const std::string& filename);
+      explicit X509_Certificate(const std::string& filename);
 
-      X509_Certificate(const std::vector<byte>& in);
+      explicit X509_Certificate(const std::vector<byte>& in);
 
    private:
       void force_decode() override;
diff --git a/src/lib/cert/x509/x509path.h b/src/lib/cert/x509/x509path.h
index 08d92915d..b7061685a 100644
--- a/src/lib/cert/x509/x509path.h
+++ b/src/lib/cert/x509/x509path.h
@@ -120,7 +120,7 @@ class BOTAN_DLL Path_Validation_Result
       Path_Validation_Result(std::vector<std::set<Certificate_Status_Code>> status,
                              std::vector<X509_Certificate>&& cert_chain);
 
-      Path_Validation_Result(Certificate_Status_Code status) : m_overall(status) {}
+      explicit Path_Validation_Result(Certificate_Status_Code status) : m_overall(status) {}
 
    private:
       friend Path_Validation_Result BOTAN_DLL x509_path_validate(
diff --git a/src/lib/compression/bzip2/bzip2.cpp b/src/lib/compression/bzip2/bzip2.cpp
index 09cd05919..d9ada84f6 100644
--- a/src/lib/compression/bzip2/bzip2.cpp
+++ b/src/lib/compression/bzip2/bzip2.cpp
@@ -37,7 +37,7 @@ class Bzip2_Stream : public Zlib_Style_Stream<bz_stream, char>
 class Bzip2_Compression_Stream : public Bzip2_Stream
    {
    public:
-      Bzip2_Compression_Stream(size_t block_size)
+      explicit Bzip2_Compression_Stream(size_t block_size)
          {
          int rc = BZ2_bzCompressInit(streamp(), block_size, 0, 0);
 
diff --git a/src/lib/compression/compression.cpp b/src/lib/compression/compression.cpp
index 178de245f..54faec7b8 100644
--- a/src/lib/compression/compression.cpp
+++ b/src/lib/compression/compression.cpp
@@ -56,7 +56,7 @@ void Compression_Alloc_Info::do_free(void* ptr)
 
 namespace {
 
-Compressor_Transform* do_make_compressor(const std::string& type, const std::string suffix)
+Compressor_Transform* do_make_compressor(const std::string& type, const std::string& suffix)
    {
    const std::map<std::string, std::string> trans{
       {"zlib", "Zlib"},
diff --git a/src/lib/compression/lzma/lzma.cpp b/src/lib/compression/lzma/lzma.cpp
index 5998d1c8c..3cc03a098 100644
--- a/src/lib/compression/lzma/lzma.cpp
+++ b/src/lib/compression/lzma/lzma.cpp
@@ -56,7 +56,7 @@ class LZMA_Stream : public Zlib_Style_Stream<lzma_stream, byte>
 class LZMA_Compression_Stream : public LZMA_Stream
    {
    public:
-      LZMA_Compression_Stream(size_t level)
+      explicit LZMA_Compression_Stream(size_t level)
          {
          lzma_ret rc = ::lzma_easy_encoder(streamp(), level, LZMA_CHECK_CRC64);
 
diff --git a/src/lib/compression/zlib/zlib.cpp b/src/lib/compression/zlib/zlib.cpp
index 8e1928826..6df5ee931 100644
--- a/src/lib/compression/zlib/zlib.cpp
+++ b/src/lib/compression/zlib/zlib.cpp
@@ -115,7 +115,7 @@ class Deflate_Compression_Stream : public Zlib_Compression_Stream
 class Deflate_Decompression_Stream : public Zlib_Decompression_Stream
    {
    public:
-      Deflate_Decompression_Stream(int wbits) : Zlib_Decompression_Stream(wbits, -1) {}
+      explicit Deflate_Decompression_Stream(int wbits) : Zlib_Decompression_Stream(wbits, -1) {}
    };
 
 class Gzip_Compression_Stream : public Zlib_Compression_Stream
@@ -140,7 +140,7 @@ class Gzip_Compression_Stream : public Zlib_Compression_Stream
 class Gzip_Decompression_Stream : public Zlib_Decompression_Stream
    {
    public:
-      Gzip_Decompression_Stream(int wbits) : Zlib_Decompression_Stream(wbits, 16) {}
+      explicit Gzip_Decompression_Stream(int wbits) : Zlib_Decompression_Stream(wbits, 16) {}
    };
 
 }
diff --git a/src/lib/entropy/cryptoapi_rng/es_capi.cpp b/src/lib/entropy/cryptoapi_rng/es_capi.cpp
index 8d682698a..c9d8fb7c4 100644
--- a/src/lib/entropy/cryptoapi_rng/es_capi.cpp
+++ b/src/lib/entropy/cryptoapi_rng/es_capi.cpp
@@ -19,7 +19,7 @@ namespace {
 class CSP_Handle
    {
    public:
-      CSP_Handle(u64bit capi_provider)
+      explicit CSP_Handle(u64bit capi_provider)
          {
          m_valid = false;
          DWORD prov_type = (DWORD)capi_provider;
diff --git a/src/lib/entropy/cryptoapi_rng/es_capi.h b/src/lib/entropy/cryptoapi_rng/es_capi.h
index a43d5a7f2..b1c60bfa1 100644
--- a/src/lib/entropy/cryptoapi_rng/es_capi.h
+++ b/src/lib/entropy/cryptoapi_rng/es_capi.h
@@ -27,7 +27,7 @@ class Win32_CAPI_EntropySource final : public Entropy_Source
      * Win32_Capi_Entropysource Constructor
      * @param provs list of providers, separated by ':'
      */
-      Win32_CAPI_EntropySource(const std::string& provs = "");
+      explicit Win32_CAPI_EntropySource(const std::string& provs = "");
    private:
       std::vector<u64bit> m_prov_types;
    };
diff --git a/src/lib/entropy/entropy_src.h b/src/lib/entropy/entropy_src.h
index 3bcd8c68d..539df809a 100644
--- a/src/lib/entropy/entropy_src.h
+++ b/src/lib/entropy/entropy_src.h
@@ -30,7 +30,7 @@ class BOTAN_DLL Entropy_Accumulator final
       * still be called again a few more times, and should be careful to return
       * true then as well.
       */
-      Entropy_Accumulator(std::function<bool (const byte[], size_t, double)> accum) :
+      explicit Entropy_Accumulator(std::function<bool (const byte[], size_t, double)> accum) :
          m_accum_fn(accum) {}
 
       /**
@@ -113,7 +113,7 @@ class BOTAN_DLL Entropy_Sources final
       bool poll_just(Entropy_Accumulator& accum, const std::string& src);
 
       Entropy_Sources() {}
-      Entropy_Sources(const std::vector<std::string>& sources);
+      explicit Entropy_Sources(const std::vector<std::string>& sources);
 
       ~Entropy_Sources();
    private:
diff --git a/src/lib/entropy/proc_walk/proc_walk.cpp b/src/lib/entropy/proc_walk/proc_walk.cpp
index 7ef6a8e26..c59a8227b 100644
--- a/src/lib/entropy/proc_walk/proc_walk.cpp
+++ b/src/lib/entropy/proc_walk/proc_walk.cpp
@@ -28,7 +28,7 @@ namespace {
 class Directory_Walker : public File_Descriptor_Source
    {
    public:
-      Directory_Walker(const std::string& root) :
+      explicit Directory_Walker(const std::string& root) :
          m_cur_dir(std::make_pair<DIR*, std::string>(nullptr, ""))
          {
          if(DIR* root_dir = ::opendir(root.c_str()))
diff --git a/src/lib/entropy/win32_stats/es_win32.cpp b/src/lib/entropy/win32_stats/es_win32.cpp
index 7cb0988db..ce0edea83 100644
--- a/src/lib/entropy/win32_stats/es_win32.cpp
+++ b/src/lib/entropy/win32_stats/es_win32.cpp
@@ -72,7 +72,6 @@ void Win32_EntropySource::poll(Entropy_Accumulator& accum)
 
    if(!accum.polling_finished())
       {
-      size_t heap_lists_found = 0;
       HEAPLIST32 heap_list;
       heap_list.dwSize = sizeof(HEAPLIST32);
 
@@ -81,6 +80,7 @@ void Win32_EntropySource::poll(Entropy_Accumulator& accum)
 
       if(Heap32ListFirst(snapshot, &heap_list))
          {
+         size_t heap_lists_found = 0;
          do
             {
             accum.add(heap_list, BOTAN_ENTROPY_ESTIMATE_SYSTEM_DATA);
@@ -88,12 +88,12 @@ void Win32_EntropySource::poll(Entropy_Accumulator& accum)
             if(++heap_lists_found > HEAP_LISTS_MAX)
                break;
 
-            size_t heap_objs_found = 0;
             HEAPENTRY32 heap_entry;
             heap_entry.dwSize = sizeof(HEAPENTRY32);
             if(Heap32First(&heap_entry, heap_list.th32ProcessID,
                            heap_list.th32HeapID))
                {
+               size_t heap_objs_found = 0;
                do
                   {
                   if(heap_objs_found++ > HEAP_OBJS_PER_LIST)
diff --git a/src/lib/ffi/ffi.cpp b/src/lib/ffi/ffi.cpp
index 621195ea3..11084ae50 100644
--- a/src/lib/ffi/ffi.cpp
+++ b/src/lib/ffi/ffi.cpp
@@ -65,7 +65,7 @@ namespace {
 class FFI_Error : public Botan::Exception
    {
    public:
-      FFI_Error(const std::string& what) : Exception("FFI error", what) {}
+      explicit FFI_Error(const std::string& what) : Exception("FFI error", what) {}
    };
 
 template<typename T, uint32_t MAGIC>
diff --git a/src/lib/filters/codec_filt/b64_filt.h b/src/lib/filters/codec_filt/b64_filt.h
index 8761cc327..f1879fb71 100644
--- a/src/lib/filters/codec_filt/b64_filt.h
+++ b/src/lib/filters/codec_filt/b64_filt.h
@@ -76,7 +76,7 @@ class BOTAN_DLL Base64_Decoder final : public Filter
       * @param checking the type of checking that shall be performed by
       * the decoder
       */
-      Base64_Decoder(Decoder_Checking checking = NONE);
+      explicit Base64_Decoder(Decoder_Checking checking = NONE);
    private:
       const Decoder_Checking m_checking;
       std::vector<byte> m_in, m_out;
diff --git a/src/lib/filters/codec_filt/hex_filt.h b/src/lib/filters/codec_filt/hex_filt.h
index cb06d223f..f8a35b8b9 100644
--- a/src/lib/filters/codec_filt/hex_filt.h
+++ b/src/lib/filters/codec_filt/hex_filt.h
@@ -33,7 +33,7 @@ class BOTAN_DLL Hex_Encoder final : public Filter
       * Create a hex encoder.
       * @param the_case the case to use in the encoded strings.
       */
-      Hex_Encoder(Case the_case);
+      explicit Hex_Encoder(Case the_case);
 
       /**
       * Create a hex encoder.
@@ -69,7 +69,7 @@ class BOTAN_DLL Hex_Decoder final : public Filter
       * character checking.
       * @param checking the checking to use during decoding.
       */
-      Hex_Decoder(Decoder_Checking checking = NONE);
+      explicit Hex_Decoder(Decoder_Checking checking = NONE);
    private:
       const Decoder_Checking m_checking;
       std::vector<byte> m_in, m_out;
diff --git a/src/lib/filters/filter.cpp b/src/lib/filters/filter.cpp
index 18ea02b9e..6ae713314 100644
--- a/src/lib/filters/filter.cpp
+++ b/src/lib/filters/filter.cpp
@@ -6,7 +6,6 @@
 */
 
 #include <botan/filter.h>
-#include <botan/secqueue.h>
 #include <botan/exceptn.h>
 
 namespace Botan {
diff --git a/src/lib/filters/filters.h b/src/lib/filters/filters.h
index 7a527dde0..4f559587f 100644
--- a/src/lib/filters/filters.h
+++ b/src/lib/filters/filters.h
@@ -67,7 +67,7 @@ class BOTAN_DLL StreamCipher_Filter : public Keyed_Filter
       * Construct a stream cipher filter.
       * @param cipher a cipher object to use
       */
-      StreamCipher_Filter(StreamCipher* cipher);
+      explicit StreamCipher_Filter(StreamCipher* cipher);
 
       /**
       * Construct a stream cipher filter.
@@ -80,7 +80,7 @@ class BOTAN_DLL StreamCipher_Filter : public Keyed_Filter
       * Construct a stream cipher filter.
       * @param cipher the name of the desired cipher
       */
-      StreamCipher_Filter(const std::string& cipher);
+      explicit StreamCipher_Filter(const std::string& cipher);
 
       /**
       * Construct a stream cipher filter.
diff --git a/src/lib/filters/pipe.h b/src/lib/filters/pipe.h
index 23e5b4c8d..286484a81 100644
--- a/src/lib/filters/pipe.h
+++ b/src/lib/filters/pipe.h
@@ -297,7 +297,7 @@ class BOTAN_DLL Pipe final : public DataSource
       * Construct a Pipe from a list of filters
       * @param filters the set of filters to use
       */
-      Pipe(std::initializer_list<Filter*> filters);
+      explicit Pipe(std::initializer_list<Filter*> filters);
 
       Pipe(const Pipe&) = delete;
       Pipe& operator=(const Pipe&) = delete;
diff --git a/src/lib/filters/pipe_rw.cpp b/src/lib/filters/pipe_rw.cpp
index 4d31f43f5..646752e7c 100644
--- a/src/lib/filters/pipe_rw.cpp
+++ b/src/lib/filters/pipe_rw.cpp
@@ -8,7 +8,6 @@
 
 #include <botan/pipe.h>
 #include <botan/internal/out_buf.h>
-#include <botan/secqueue.h>
 
 namespace Botan {
 
diff --git a/src/lib/filters/secqueue.cpp b/src/lib/filters/secqueue.cpp
index 4546ae398..6f4070813 100644
--- a/src/lib/filters/secqueue.cpp
+++ b/src/lib/filters/secqueue.cpp
@@ -104,6 +104,7 @@ void SecureQueue::destroy()
 SecureQueue& SecureQueue::operator=(const SecureQueue& input)
    {
    destroy();
+   m_bytes_read = input.get_bytes_read();
    m_head = m_tail = new SecureQueueNode;
    SecureQueueNode* temp = input.m_head;
    while(temp)
diff --git a/src/lib/filters/transform_filter.h b/src/lib/filters/transform_filter.h
index 3dd68405b..2ecc5cecb 100644
--- a/src/lib/filters/transform_filter.h
+++ b/src/lib/filters/transform_filter.h
@@ -21,7 +21,7 @@ class BOTAN_DLL Transform_Filter : public Keyed_Filter,
                                    private Buffered_Filter
    {
    public:
-      Transform_Filter(Transform* t);
+      explicit Transform_Filter(Transform* t);
 
       void set_iv(const InitializationVector& iv) override;
 
@@ -49,7 +49,7 @@ class BOTAN_DLL Transform_Filter : public Keyed_Filter,
       class Nonce_State
          {
          public:
-            Nonce_State(bool allow_null_nonce) : m_fresh_nonce(allow_null_nonce) {}
+            explicit Nonce_State(bool allow_null_nonce) : m_fresh_nonce(allow_null_nonce) {}
 
             void update(const InitializationVector& iv);
             std::vector<byte> get();
diff --git a/src/lib/hash/blake2/blake2b.h b/src/lib/hash/blake2/blake2b.h
index efe0d34f4..290db10f0 100644
--- a/src/lib/hash/blake2/blake2b.h
+++ b/src/lib/hash/blake2/blake2b.h
@@ -29,7 +29,7 @@ class BOTAN_DLL Blake2b final : public HashFunction
       /**
       * @param output_bits the output size of Blake2b in bits
       */
-      Blake2b(size_t output_bits = 512);
+      explicit Blake2b(size_t output_bits = 512);
 
       size_t hash_block_size() const override { return BLAKE2B_BLOCKBYTES; }
       size_t output_length() const override { return m_output_bits / 8; }
diff --git a/src/lib/hash/hash.cpp b/src/lib/hash/hash.cpp
index b6a7ca50d..9a15c7998 100644
--- a/src/lib/hash/hash.cpp
+++ b/src/lib/hash/hash.cpp
@@ -98,7 +98,7 @@ namespace Botan {
 std::unique_ptr<HashFunction> HashFunction::create(const std::string& algo_spec,
                                                    const std::string& provider)
    {
-   return std::unique_ptr<HashFunction>(make_a<HashFunction>(algo_spec, provider));
+   return std::unique_ptr<HashFunction>(make_a<HashFunction>(Botan::HashFunction::Spec(algo_spec), provider));
    }
 
 std::vector<std::string> HashFunction::providers(const std::string& algo_spec)
diff --git a/src/lib/hash/keccak/keccak.h b/src/lib/hash/keccak/keccak.h
index 7929dd502..a73595d6a 100644
--- a/src/lib/hash/keccak/keccak.h
+++ b/src/lib/hash/keccak/keccak.h
@@ -25,7 +25,7 @@ class BOTAN_DLL Keccak_1600 final : public HashFunction
       * @param output_bits the size of the hash output; must be one of
       *                    224, 256, 384, or 512
       */
-      Keccak_1600(size_t output_bits = 512);
+      explicit Keccak_1600(size_t output_bits = 512);
 
       size_t hash_block_size() const override { return m_bitrate / 8; }
       size_t output_length() const override { return m_output_bits / 8; }
diff --git a/src/lib/hash/md2/md2.h b/src/lib/hash/md2/md2.h
index ab29a49cb..58629495a 100644
--- a/src/lib/hash/md2/md2.h
+++ b/src/lib/hash/md2/md2.h
@@ -25,7 +25,7 @@ class BOTAN_DLL MD2 final : public HashFunction
 
       void clear() override;
 
-      MD2() : m_X(48), m_checksum(16), m_buffer(16)
+      MD2() : m_X(48), m_checksum(16), m_buffer(16), m_position(0)
          { clear(); }
    private:
       void add_data(const byte[], size_t) override;
diff --git a/src/lib/hash/par_hash/par_hash.h b/src/lib/hash/par_hash/par_hash.h
index b0e2ff828..3a93f4e8e 100644
--- a/src/lib/hash/par_hash/par_hash.h
+++ b/src/lib/hash/par_hash/par_hash.h
@@ -28,7 +28,7 @@ class BOTAN_DLL Parallel final : public HashFunction
       /**
       * @param hashes a set of hashes to compute in parallel
       */
-      Parallel(const std::vector<HashFunction*>& hashes);
+      explicit Parallel(const std::vector<HashFunction*>& hashes);
 
       Parallel(const Parallel&) = delete;
       Parallel& operator=(const Parallel&) = delete;
diff --git a/src/lib/hash/sha1/sha160.h b/src/lib/hash/sha1/sha160.h
index 2f5d9b16e..b4a161c14 100644
--- a/src/lib/hash/sha1/sha160.h
+++ b/src/lib/hash/sha1/sha160.h
@@ -35,7 +35,7 @@ class BOTAN_DLL SHA_160 : public MDx_HashFunction
       * constraints
       * @param W_size how big to make W
       */
-      SHA_160(size_t W_size) :
+      explicit SHA_160(size_t W_size) :
          MDx_HashFunction(64, true, true), m_digest(5), m_W(W_size)
          {
          clear();
diff --git a/src/lib/kdf/hkdf/hkdf.h b/src/lib/kdf/hkdf/hkdf.h
index d4e4006ca..3e3e2b73a 100644
--- a/src/lib/kdf/hkdf/hkdf.h
+++ b/src/lib/kdf/hkdf/hkdf.h
@@ -21,7 +21,7 @@ namespace Botan {
 class BOTAN_DLL HKDF final : public KDF
    {
    public:
-      HKDF(MessageAuthenticationCode* prf) : m_prf(prf) {}
+      explicit HKDF(MessageAuthenticationCode* prf) : m_prf(prf) {}
 
       static HKDF* make(const Spec& spec);
 
diff --git a/src/lib/kdf/kdf.cpp b/src/lib/kdf/kdf.cpp
index cf13c4803..45ee165e0 100644
--- a/src/lib/kdf/kdf.cpp
+++ b/src/lib/kdf/kdf.cpp
@@ -48,7 +48,7 @@ KDF::~KDF() {}
 std::unique_ptr<KDF> KDF::create(const std::string& algo_spec,
                                                  const std::string& provider)
    {
-   return std::unique_ptr<KDF>(make_a<KDF>(algo_spec, provider));
+   return std::unique_ptr<KDF>(make_a<KDF>(Botan::KDF::Spec(algo_spec), provider));
    }
 
 std::vector<std::string> KDF::providers(const std::string& algo_spec)
diff --git a/src/lib/kdf/kdf1/kdf1.h b/src/lib/kdf/kdf1/kdf1.h
index 2697685ac..adaa84894 100644
--- a/src/lib/kdf/kdf1/kdf1.h
+++ b/src/lib/kdf/kdf1/kdf1.h
@@ -27,7 +27,7 @@ class BOTAN_DLL KDF1 final : public KDF
                  const byte secret[], size_t secret_len,
                  const byte salt[], size_t salt_len) const override;
 
-      KDF1(HashFunction* h) : m_hash(h) {}
+      explicit KDF1(HashFunction* h) : m_hash(h) {}
    private:
       std::unique_ptr<HashFunction> m_hash;
    };
diff --git a/src/lib/kdf/kdf2/kdf2.h b/src/lib/kdf/kdf2/kdf2.h
index ad62ed301..7403df21c 100644
--- a/src/lib/kdf/kdf2/kdf2.h
+++ b/src/lib/kdf/kdf2/kdf2.h
@@ -27,7 +27,7 @@ class BOTAN_DLL KDF2 final : public KDF
                  const byte secret[], size_t secret_len,
                  const byte salt[], size_t salt_len) const override;
 
-      KDF2(HashFunction* h) : m_hash(h) {}
+      explicit KDF2(HashFunction* h) : m_hash(h) {}
    private:
       std::unique_ptr<HashFunction> m_hash;
    };
diff --git a/src/lib/kdf/prf_tls/prf_tls.h b/src/lib/kdf/prf_tls/prf_tls.h
index f000484a7..a51006d88 100644
--- a/src/lib/kdf/prf_tls/prf_tls.h
+++ b/src/lib/kdf/prf_tls/prf_tls.h
@@ -47,7 +47,7 @@ class BOTAN_DLL TLS_12_PRF final : public KDF
                  const byte secret[], size_t secret_len,
                  const byte salt[], size_t salt_len) const override;
 
-      TLS_12_PRF(MessageAuthenticationCode* mac) : m_mac(mac) {}
+      explicit TLS_12_PRF(MessageAuthenticationCode* mac) : m_mac(mac) {}
 
       static TLS_12_PRF* make(const Spec& spec);
    private:
diff --git a/src/lib/kdf/prf_x942/prf_x942.h b/src/lib/kdf/prf_x942/prf_x942.h
index f31036649..c15be9845 100644
--- a/src/lib/kdf/prf_x942/prf_x942.h
+++ b/src/lib/kdf/prf_x942/prf_x942.h
@@ -26,7 +26,7 @@ class BOTAN_DLL X942_PRF final : public KDF
                  const byte secret[], size_t secret_len,
                  const byte salt[], size_t salt_len) const override;
 
-      X942_PRF(const std::string& oid);
+      explicit X942_PRF(const std::string& oid);
    private:
       std::string m_key_wrap_oid;
    };
diff --git a/src/lib/mac/cbc_mac/cbc_mac.h b/src/lib/mac/cbc_mac/cbc_mac.h
index 06d1dc852..cd2ebd18f 100644
--- a/src/lib/mac/cbc_mac/cbc_mac.h
+++ b/src/lib/mac/cbc_mac/cbc_mac.h
@@ -32,7 +32,7 @@ class BOTAN_DLL CBC_MAC final : public MessageAuthenticationCode
       /**
       * @param cipher the underlying block cipher to use
       */
-      CBC_MAC(BlockCipher* cipher);
+      explicit CBC_MAC(BlockCipher* cipher);
 
       static CBC_MAC* make(const Spec& spec);
    private:
diff --git a/src/lib/mac/cmac/cmac.h b/src/lib/mac/cmac/cmac.h
index 5a38de28d..0e973b79d 100644
--- a/src/lib/mac/cmac/cmac.h
+++ b/src/lib/mac/cmac/cmac.h
@@ -40,7 +40,7 @@ class BOTAN_DLL CMAC final : public MessageAuthenticationCode
       /**
       * @param cipher the underlying block cipher to use
       */
-      CMAC(BlockCipher* cipher);
+      explicit CMAC(BlockCipher* cipher);
 
       static CMAC* make(const Spec& spec);
 
diff --git a/src/lib/mac/hmac/hmac.h b/src/lib/mac/hmac/hmac.h
index 5154739d2..654a167e7 100644
--- a/src/lib/mac/hmac/hmac.h
+++ b/src/lib/mac/hmac/hmac.h
@@ -34,7 +34,7 @@ class BOTAN_DLL HMAC final : public MessageAuthenticationCode
       /**
       * @param hash the hash to use for HMACing
       */
-      HMAC(HashFunction* hash);
+      explicit HMAC(HashFunction* hash);
 
       static HMAC* make(const Spec& spec);
 
diff --git a/src/lib/mac/mac.cpp b/src/lib/mac/mac.cpp
index 8c1185c55..a3917141d 100644
--- a/src/lib/mac/mac.cpp
+++ b/src/lib/mac/mac.cpp
@@ -38,7 +38,7 @@ namespace Botan {
 std::unique_ptr<MessageAuthenticationCode> MessageAuthenticationCode::create(const std::string& algo_spec,
                                                                              const std::string& provider)
    {
-   return std::unique_ptr<MessageAuthenticationCode>(make_a<MessageAuthenticationCode>(algo_spec, provider));
+   return std::unique_ptr<MessageAuthenticationCode>(make_a<MessageAuthenticationCode>(MessageAuthenticationCode::Spec(algo_spec), provider));
    }
 
 std::vector<std::string> MessageAuthenticationCode::providers(const std::string& algo_spec)
diff --git a/src/lib/math/ec_gfp/point_gfp.h b/src/lib/math/ec_gfp/point_gfp.h
index 206e43155..c64963683 100644
--- a/src/lib/math/ec_gfp/point_gfp.h
+++ b/src/lib/math/ec_gfp/point_gfp.h
@@ -21,7 +21,7 @@ namespace Botan {
 */
 struct BOTAN_DLL Illegal_Transformation : public Exception
    {
-   Illegal_Transformation(const std::string& err =
+   explicit Illegal_Transformation(const std::string& err =
                           "Requested transformation is not possible") :
       Exception(err) {}
    };
@@ -31,7 +31,7 @@ struct BOTAN_DLL Illegal_Transformation : public Exception
 */
 struct BOTAN_DLL Illegal_Point : public Exception
    {
-   Illegal_Point(const std::string& err = "Malformed ECP point detected") :
+   explicit Illegal_Point(const std::string& err = "Malformed ECP point detected") :
       Exception(err) {}
    };
 
@@ -56,7 +56,7 @@ class BOTAN_DLL PointGFp
       * Construct the zero point
       * @param curve The base curve
       */
-      PointGFp(const CurveGFp& curve);
+      explicit PointGFp(const CurveGFp& curve);
 
       static PointGFp zero_of(const CurveGFp& curve)
          {
diff --git a/src/lib/math/numbertheory/dsa_gen.cpp b/src/lib/math/numbertheory/dsa_gen.cpp
index 1f922fd49..42bfeb4c1 100644
--- a/src/lib/math/numbertheory/dsa_gen.cpp
+++ b/src/lib/math/numbertheory/dsa_gen.cpp
@@ -61,7 +61,7 @@ bool generate_dsa_primes(RandomNumberGenerator& rng,
    class Seed
       {
       public:
-         Seed(const std::vector<byte>& s) : m_seed(s) {}
+         explicit Seed(const std::vector<byte>& s) : m_seed(s) {}
 
          operator std::vector<byte>& () { return m_seed; }
 
diff --git a/src/lib/math/numbertheory/pow_mod.cpp b/src/lib/math/numbertheory/pow_mod.cpp
index 49ff6cca2..5503f313c 100644
--- a/src/lib/math/numbertheory/pow_mod.cpp
+++ b/src/lib/math/numbertheory/pow_mod.cpp
@@ -34,10 +34,15 @@ Power_Mod::Power_Mod(const Power_Mod& other)
 */
 Power_Mod& Power_Mod::operator=(const Power_Mod& other)
    {
-   delete m_core;
-   m_core = nullptr;
-   if(other.m_core)
-      m_core = other.m_core->copy();
+   if(this != &other)
+      {
+      delete m_core;
+      m_core = nullptr;
+      if(other.m_core)
+         {
+         m_core = other.m_core->copy();
+         }
+      }
    return (*this);
    }
 
diff --git a/src/lib/math/numbertheory/powm_fw.cpp b/src/lib/math/numbertheory/powm_fw.cpp
index 02e9bbe83..7369959a9 100644
--- a/src/lib/math/numbertheory/powm_fw.cpp
+++ b/src/lib/math/numbertheory/powm_fw.cpp
@@ -60,10 +60,7 @@ BigInt Fixed_Window_Exponentiator::execute() const
 */
 Fixed_Window_Exponentiator::Fixed_Window_Exponentiator(const BigInt& n,
                                                        Power_Mod::Usage_Hints hints)
-   {
-   m_reducer = Modular_Reducer(n);
-   m_hints = hints;
-   m_window_bits = 0;
-   }
+      : m_reducer{Modular_Reducer(n)}, m_exp{}, m_window_bits{}, m_g{}, m_hints{hints}
+   {}
 
 }
diff --git a/src/lib/math/numbertheory/reducer.h b/src/lib/math/numbertheory/reducer.h
index 248de3e2f..36808f00f 100644
--- a/src/lib/math/numbertheory/reducer.h
+++ b/src/lib/math/numbertheory/reducer.h
@@ -50,7 +50,7 @@ class BOTAN_DLL Modular_Reducer
       bool initialized() const { return (m_mod_words != 0); }
 
       Modular_Reducer() { m_mod_words = 0; }
-      Modular_Reducer(const BigInt& mod);
+      explicit Modular_Reducer(const BigInt& mod);
    private:
       BigInt m_modulus, m_modulus_2, m_mu;
       size_t m_mod_words;
diff --git a/src/lib/misc/srp6/srp6_files.h b/src/lib/misc/srp6/srp6_files.h
index 7d6d9a55b..2b20de7a3 100644
--- a/src/lib/misc/srp6/srp6_files.h
+++ b/src/lib/misc/srp6/srp6_files.h
@@ -24,7 +24,7 @@ class BOTAN_DLL SRP6_Authenticator_File
       * @param filename will be opened and processed as a SRP
       * authenticator file
       */
-      SRP6_Authenticator_File(const std::string& filename);
+      explicit SRP6_Authenticator_File(const std::string& filename);
 
       bool lookup_user(const std::string& username,
                        BigInt& v,
diff --git a/src/lib/misc/tss/tss.h b/src/lib/misc/tss/tss.h
index 68eb5158f..6ff47a0cc 100644
--- a/src/lib/misc/tss/tss.h
+++ b/src/lib/misc/tss/tss.h
@@ -46,7 +46,7 @@ class BOTAN_DLL RTSS_Share
       /**
       * @param hex_input the share encoded in hexadecimal
       */
-      RTSS_Share(const std::string& hex_input);
+      explicit RTSS_Share(const std::string& hex_input);
 
       /**
       * @return hex representation
diff --git a/src/lib/modes/aead/ocb/ocb.cpp b/src/lib/modes/aead/ocb/ocb.cpp
index 08157cd47..77126ec7a 100644
--- a/src/lib/modes/aead/ocb/ocb.cpp
+++ b/src/lib/modes/aead/ocb/ocb.cpp
@@ -15,7 +15,7 @@ namespace Botan {
 class L_computer
    {
    public:
-      L_computer(const BlockCipher& cipher)
+      explicit L_computer(const BlockCipher& cipher)
          {
          m_L_star.resize(cipher.block_size());
          cipher.encrypt(m_L_star);
diff --git a/src/lib/modes/aead/siv/siv.h b/src/lib/modes/aead/siv/siv.h
index d46c7dcfd..d3e4c5270 100644
--- a/src/lib/modes/aead/siv/siv.h
+++ b/src/lib/modes/aead/siv/siv.h
@@ -43,7 +43,7 @@ class BOTAN_DLL SIV_Mode : public AEAD_Mode
       size_t tag_size() const override { return 16; }
 
    protected:
-      SIV_Mode(BlockCipher* cipher);
+      explicit SIV_Mode(BlockCipher* cipher);
 
       StreamCipher& ctr() { return *m_ctr; }
 
@@ -73,7 +73,7 @@ class BOTAN_DLL SIV_Encryption final : public SIV_Mode
       /**
       * @param cipher a block cipher
       */
-      SIV_Encryption(BlockCipher* cipher) : SIV_Mode(cipher) {}
+      explicit SIV_Encryption(BlockCipher* cipher) : SIV_Mode(cipher) {}
 
       void finish(secure_vector<byte>& final_block, size_t offset = 0) override;
 
@@ -92,7 +92,7 @@ class BOTAN_DLL SIV_Decryption final : public SIV_Mode
       /**
       * @param cipher a 128-bit block cipher
       */
-      SIV_Decryption(BlockCipher* cipher) : SIV_Mode(cipher) {}
+      explicit SIV_Decryption(BlockCipher* cipher) : SIV_Mode(cipher) {}
 
       void finish(secure_vector<byte>& final_block, size_t offset = 0) override;
 
diff --git a/src/lib/modes/cbc/cbc.h b/src/lib/modes/cbc/cbc.h
index 9a767d3a0..961991d4a 100644
--- a/src/lib/modes/cbc/cbc.h
+++ b/src/lib/modes/cbc/cbc.h
@@ -80,7 +80,7 @@ class BOTAN_DLL CBC_Encryption : public CBC_Mode
 class BOTAN_DLL CTS_Encryption final : public CBC_Encryption
    {
    public:
-      CTS_Encryption(BlockCipher* cipher) : CBC_Encryption(cipher, nullptr) {}
+      explicit CTS_Encryption(BlockCipher* cipher) : CBC_Encryption(cipher, nullptr) {}
 
       size_t output_length(size_t input_length) const override;
 
@@ -117,7 +117,7 @@ class BOTAN_DLL CBC_Decryption : public CBC_Mode
 class BOTAN_DLL CTS_Decryption final : public CBC_Decryption
    {
    public:
-      CTS_Decryption(BlockCipher* cipher) : CBC_Decryption(cipher, nullptr) {}
+      explicit CTS_Decryption(BlockCipher* cipher) : CBC_Decryption(cipher, nullptr) {}
 
       void finish(secure_vector<byte>& final_block, size_t offset = 0) override;
 
diff --git a/src/lib/modes/stream_mode.h b/src/lib/modes/stream_mode.h
index 5450bc37d..f5f1aa33a 100644
--- a/src/lib/modes/stream_mode.h
+++ b/src/lib/modes/stream_mode.h
@@ -15,7 +15,7 @@ namespace Botan {
 class BOTAN_DLL Stream_Cipher_Mode : public Cipher_Mode
    {
    public:
-      Stream_Cipher_Mode(StreamCipher* cipher) : m_cipher(cipher) {}
+      explicit Stream_Cipher_Mode(StreamCipher* cipher) : m_cipher(cipher) {}
 
       void update(secure_vector<byte>& buf, size_t offset) override
          {
diff --git a/src/lib/modes/xts/xts.h b/src/lib/modes/xts/xts.h
index 2df18e82f..e751b1644 100644
--- a/src/lib/modes/xts/xts.h
+++ b/src/lib/modes/xts/xts.h
@@ -33,7 +33,7 @@ class BOTAN_DLL XTS_Mode : public Cipher_Mode
 
       void clear() override;
    protected:
-      XTS_Mode(BlockCipher* cipher);
+      explicit XTS_Mode(BlockCipher* cipher);
 
       const byte* tweak() const { return m_tweak.data(); }
 
@@ -55,7 +55,7 @@ class BOTAN_DLL XTS_Mode : public Cipher_Mode
 class BOTAN_DLL XTS_Encryption final : public XTS_Mode
    {
    public:
-      XTS_Encryption(BlockCipher* cipher) : XTS_Mode(cipher) {}
+      explicit XTS_Encryption(BlockCipher* cipher) : XTS_Mode(cipher) {}
 
       void update(secure_vector<byte>& blocks, size_t offset = 0) override;
 
@@ -70,7 +70,7 @@ class BOTAN_DLL XTS_Encryption final : public XTS_Mode
 class BOTAN_DLL XTS_Decryption final : public XTS_Mode
    {
    public:
-      XTS_Decryption(BlockCipher* cipher) : XTS_Mode(cipher) {}
+      explicit XTS_Decryption(BlockCipher* cipher) : XTS_Mode(cipher) {}
 
       void update(secure_vector<byte>& blocks, size_t offset = 0) override;
 
diff --git a/src/lib/pbkdf/pbkdf.cpp b/src/lib/pbkdf/pbkdf.cpp
index 98722fcc6..01f52853a 100644
--- a/src/lib/pbkdf/pbkdf.cpp
+++ b/src/lib/pbkdf/pbkdf.cpp
@@ -34,7 +34,7 @@ PBKDF::~PBKDF() {}
 std::unique_ptr<PBKDF> PBKDF::create(const std::string& algo_spec,
                                      const std::string& provider)
    {
-   return std::unique_ptr<PBKDF>(make_a<PBKDF>(algo_spec, provider));
+   return std::unique_ptr<PBKDF>(make_a<PBKDF>(Botan::PBKDF::Spec(algo_spec), provider));
    }
 
 std::vector<std::string> PBKDF::providers(const std::string& algo_spec)
diff --git a/src/lib/pbkdf/pbkdf1/pbkdf1.h b/src/lib/pbkdf/pbkdf1/pbkdf1.h
index 22b04a3a0..cd10b3112 100644
--- a/src/lib/pbkdf/pbkdf1/pbkdf1.h
+++ b/src/lib/pbkdf/pbkdf1/pbkdf1.h
@@ -25,7 +25,7 @@ class BOTAN_DLL PKCS5_PBKDF1 final : public PBKDF
       * Create a PKCS #5 instance using the specified hash function.
       * @param hash pointer to a hash function object to use
       */
-      PKCS5_PBKDF1(HashFunction* hash) : m_hash(hash) {}
+      explicit PKCS5_PBKDF1(HashFunction* hash) : m_hash(hash) {}
 
       std::string name() const override
          {
diff --git a/src/lib/pbkdf/pbkdf2/pbkdf2.h b/src/lib/pbkdf/pbkdf2/pbkdf2.h
index 1918f5dd2..4f77f338b 100644
--- a/src/lib/pbkdf/pbkdf2/pbkdf2.h
+++ b/src/lib/pbkdf/pbkdf2/pbkdf2.h
@@ -48,7 +48,7 @@ class BOTAN_DLL PKCS5_PBKDF2 final : public PBKDF
       * Create a PKCS #5 instance using the specified message auth code
       * @param mac_fn the MAC object to use as PRF
       */
-      PKCS5_PBKDF2(MessageAuthenticationCode* mac_fn) : m_mac(mac_fn) {}
+      explicit PKCS5_PBKDF2(MessageAuthenticationCode* mac_fn) : m_mac(mac_fn) {}
 
       static PKCS5_PBKDF2* make(const Spec& spec);
    private:
diff --git a/src/lib/pk_pad/eme.cpp b/src/lib/pk_pad/eme.cpp
index 4804a8a81..623c3777e 100644
--- a/src/lib/pk_pad/eme.cpp
+++ b/src/lib/pk_pad/eme.cpp
@@ -44,7 +44,7 @@ EME* get_eme(const std::string& algo_spec)
    {
    SCAN_Name request(algo_spec);
 
-   if(EME* eme = make_a<EME>(algo_spec))
+   if(EME* eme = make_a<EME>(Botan::EME::Spec(algo_spec)))
       return eme;
 
    if(request.algo_name() == "Raw")
diff --git a/src/lib/pk_pad/emsa.cpp b/src/lib/pk_pad/emsa.cpp
index e20286a7d..3b8641357 100644
--- a/src/lib/pk_pad/emsa.cpp
+++ b/src/lib/pk_pad/emsa.cpp
@@ -39,7 +39,7 @@ EMSA* get_emsa(const std::string& algo_spec)
    {
    SCAN_Name request(algo_spec);
 
-   if(EMSA* emsa = make_a<EMSA>(algo_spec))
+   if(EMSA* emsa = make_a<EMSA>(Botan::EMSA::Spec(algo_spec)))
       return emsa;
 
    throw Algorithm_Not_Found(algo_spec);
diff --git a/src/lib/pk_pad/emsa1/emsa1.h b/src/lib/pk_pad/emsa1/emsa1.h
index 3e10162b2..e346167da 100644
--- a/src/lib/pk_pad/emsa1/emsa1.h
+++ b/src/lib/pk_pad/emsa1/emsa1.h
@@ -23,7 +23,7 @@ class BOTAN_DLL EMSA1 : public EMSA
       /**
       * @param hash the hash function to use
       */
-      EMSA1(HashFunction* hash) : m_hash(hash) {}
+      explicit EMSA1(HashFunction* hash) : m_hash(hash) {}
 
    protected:
       size_t hash_output_length() const { return m_hash->output_length(); }
diff --git a/src/lib/pk_pad/emsa1_bsi/emsa1_bsi.h b/src/lib/pk_pad/emsa1_bsi/emsa1_bsi.h
index f00c0a101..a7fae6c23 100644
--- a/src/lib/pk_pad/emsa1_bsi/emsa1_bsi.h
+++ b/src/lib/pk_pad/emsa1_bsi/emsa1_bsi.h
@@ -24,7 +24,7 @@ class BOTAN_DLL EMSA1_BSI final : public EMSA1
       /**
       * @param hash the hash object to use
       */
-      EMSA1_BSI(HashFunction* hash) : EMSA1(hash) {}
+      explicit EMSA1_BSI(HashFunction* hash) : EMSA1(hash) {}
    private:
       secure_vector<byte> encoding_of(const secure_vector<byte>&, size_t,
                                      RandomNumberGenerator& rng) override;
diff --git a/src/lib/pk_pad/emsa_pkcs1/emsa_pkcs1.h b/src/lib/pk_pad/emsa_pkcs1/emsa_pkcs1.h
index f217af764..9d5bc7829 100644
--- a/src/lib/pk_pad/emsa_pkcs1/emsa_pkcs1.h
+++ b/src/lib/pk_pad/emsa_pkcs1/emsa_pkcs1.h
@@ -26,7 +26,7 @@ class BOTAN_DLL EMSA_PKCS1v15 final : public EMSA
       /**
       * @param hash the hash object to use
       */
-      EMSA_PKCS1v15(HashFunction* hash);
+      explicit EMSA_PKCS1v15(HashFunction* hash);
 
       void update(const byte[], size_t) override;
 
diff --git a/src/lib/pk_pad/emsa_pssr/pssr.h b/src/lib/pk_pad/emsa_pssr/pssr.h
index edbda4640..ee234b0b6 100644
--- a/src/lib/pk_pad/emsa_pssr/pssr.h
+++ b/src/lib/pk_pad/emsa_pssr/pssr.h
@@ -23,7 +23,7 @@ class BOTAN_DLL PSSR final : public EMSA
       /**
       * @param hash the hash object to use
       */
-      PSSR(HashFunction* hash);
+      explicit PSSR(HashFunction* hash);
 
       /**
       * @param hash the hash object to use
diff --git a/src/lib/pk_pad/emsa_x931/emsa_x931.h b/src/lib/pk_pad/emsa_x931/emsa_x931.h
index 3372ac13c..400042a86 100644
--- a/src/lib/pk_pad/emsa_x931/emsa_x931.h
+++ b/src/lib/pk_pad/emsa_x931/emsa_x931.h
@@ -24,7 +24,7 @@ class BOTAN_DLL EMSA_X931 final : public EMSA
       /**
       * @param hash the hash object to use
       */
-      EMSA_X931(HashFunction* hash);
+      explicit EMSA_X931(HashFunction* hash);
    private:
       void update(const byte[], size_t) override;
       secure_vector<byte> raw_data() override;
diff --git a/src/lib/prov/openssl/openssl_rc4.cpp b/src/lib/prov/openssl/openssl_rc4.cpp
index 79ad98ca4..e36535e08 100644
--- a/src/lib/prov/openssl/openssl_rc4.cpp
+++ b/src/lib/prov/openssl/openssl_rc4.cpp
@@ -43,7 +43,7 @@ class OpenSSL_RC4 : public StreamCipher
          return Key_Length_Specification(1, 32);
          }
 
-      OpenSSL_RC4(size_t skip = 0) : m_skip(skip) { clear(); }
+      explicit OpenSSL_RC4(size_t skip = 0) : m_skip(skip) { clear(); }
       ~OpenSSL_RC4() { clear(); }
    private:
       void cipher(const byte in[], byte out[], size_t length) override
diff --git a/src/lib/pubkey/blinding.cpp b/src/lib/pubkey/blinding.cpp
index 4a5c5acff..b20a30fa1 100644
--- a/src/lib/pubkey/blinding.cpp
+++ b/src/lib/pubkey/blinding.cpp
@@ -19,11 +19,8 @@ namespace Botan {
 Blinder::Blinder(const BigInt& modulus,
                  std::function<BigInt (const BigInt&)> fwd,
                  std::function<BigInt (const BigInt&)> inv) :
-   m_fwd_fn(fwd), m_inv_fn(inv)
+      m_reducer{Modular_Reducer(modulus)}, m_rng{}, m_fwd_fn(fwd), m_inv_fn(inv), m_modulus_bits{modulus.bits()}, m_e{}, m_d{}, m_counter{}
    {
-   m_reducer = Modular_Reducer(modulus);
-   m_modulus_bits = modulus.bits();
-
 #if defined(BOTAN_HAS_SYSTEM_RNG)
    m_rng.reset(new System_RNG);
 #else
diff --git a/src/lib/pubkey/curve25519/curve25519.h b/src/lib/pubkey/curve25519/curve25519.h
index c3e3d4e60..9d2868d6d 100644
--- a/src/lib/pubkey/curve25519/curve25519.h
+++ b/src/lib/pubkey/curve25519/curve25519.h
@@ -32,7 +32,7 @@ class BOTAN_DLL Curve25519_PublicKey : public virtual Public_Key
       Curve25519_PublicKey(const AlgorithmIdentifier& alg_id,
                            const secure_vector<byte>& key_bits);
 
-      Curve25519_PublicKey(const secure_vector<byte>& pub) : m_public(pub) {}
+      explicit Curve25519_PublicKey(const secure_vector<byte>& pub) : m_public(pub) {}
    protected:
       Curve25519_PublicKey() {}
       secure_vector<byte> m_public;
@@ -47,9 +47,9 @@ class BOTAN_DLL Curve25519_PrivateKey : public Curve25519_PublicKey,
                             const secure_vector<byte>& key_bits,
                             RandomNumberGenerator& rng);
 
-      Curve25519_PrivateKey(RandomNumberGenerator& rng);
+      explicit Curve25519_PrivateKey(RandomNumberGenerator& rng);
 
-      Curve25519_PrivateKey(const secure_vector<byte>& secret_key);
+      explicit Curve25519_PrivateKey(const secure_vector<byte>& secret_key);
 
       std::vector<byte> public_value() const override { return Curve25519_PublicKey::public_value(); }
 
diff --git a/src/lib/pubkey/dsa/dsa.cpp b/src/lib/pubkey/dsa/dsa.cpp
index 63b7bd07e..471189cd8 100644
--- a/src/lib/pubkey/dsa/dsa.cpp
+++ b/src/lib/pubkey/dsa/dsa.cpp
@@ -140,13 +140,10 @@ class DSA_Verification_Operation : public PK_Ops::Verification_with_EMSA
       DSA_Verification_Operation(const DSA_PublicKey& dsa,
                                  const std::string& emsa) :
          PK_Ops::Verification_with_EMSA(emsa),
-         m_q(dsa.group_q()), m_y(dsa.get_y())
-         {
-         m_powermod_g_p = Fixed_Base_Power_Mod(dsa.group_g(), dsa.group_p());
-         m_powermod_y_p = Fixed_Base_Power_Mod(m_y, dsa.group_p());
-         m_mod_p = Modular_Reducer(dsa.group_p());
-         m_mod_q = Modular_Reducer(dsa.group_q());
-         }
+         m_q(dsa.group_q()), m_y(dsa.get_y()), m_powermod_g_p{Fixed_Base_Power_Mod(dsa.group_g(), dsa.group_p())},
+         m_powermod_y_p{Fixed_Base_Power_Mod(m_y, dsa.group_p())}, m_mod_p{Modular_Reducer(dsa.group_p())},
+         m_mod_q{Modular_Reducer(dsa.group_q())}
+         {}
 
       size_t message_parts() const override { return 2; }
       size_t message_part_size() const override { return m_q.bytes(); }
diff --git a/src/lib/pubkey/ec_group/ec_group.h b/src/lib/pubkey/ec_group/ec_group.h
index c7e52b238..a03b97a68 100644
--- a/src/lib/pubkey/ec_group/ec_group.h
+++ b/src/lib/pubkey/ec_group/ec_group.h
@@ -54,13 +54,13 @@ class BOTAN_DLL EC_Group
       * Decode a BER encoded ECC domain parameter set
       * @param ber_encoding the bytes of the BER encoding
       */
-      EC_Group(const std::vector<byte>& ber_encoding);
+      explicit EC_Group(const std::vector<byte>& ber_encoding);
 
       /**
       * Create an EC domain by OID (or throw if unknown)
       * @param oid the OID of the EC domain to create
       */
-      EC_Group(const OID& oid);
+      explicit EC_Group(const OID& oid);
 
       /**
       * Create an EC domain from PEM encoding (as from PEM_encode), or
diff --git a/src/lib/pubkey/ecc_key/ecc_key.cpp b/src/lib/pubkey/ecc_key/ecc_key.cpp
index a3f0ea93d..2dca20725 100644
--- a/src/lib/pubkey/ecc_key/ecc_key.cpp
+++ b/src/lib/pubkey/ecc_key/ecc_key.cpp
@@ -33,13 +33,8 @@ EC_PublicKey::EC_PublicKey(const EC_Group& dom_par,
    }
 
 EC_PublicKey::EC_PublicKey(const AlgorithmIdentifier& alg_id,
-                           const secure_vector<byte>& key_bits)
-   {
-   m_domain_params = EC_Group(alg_id.parameters);
-   m_domain_encoding = EC_DOMPAR_ENC_EXPLICIT;
-
-   m_public_key = OS2ECP(key_bits, domain().get_curve());
-   }
+                           const secure_vector<byte>& key_bits) : m_domain_params{EC_Group(alg_id.parameters)}, m_public_key{OS2ECP(key_bits, domain().get_curve())}, m_domain_encoding{EC_DOMPAR_ENC_EXPLICIT}
+   {}
 
 bool EC_PublicKey::check_key(RandomNumberGenerator&,
                              bool) const
diff --git a/src/lib/pubkey/ecc_key/ecc_key.h b/src/lib/pubkey/ecc_key/ecc_key.h
index 3557d0266..3f93a908c 100644
--- a/src/lib/pubkey/ecc_key/ecc_key.h
+++ b/src/lib/pubkey/ecc_key/ecc_key.h
@@ -81,7 +81,8 @@ class BOTAN_DLL EC_PublicKey : public virtual Public_Key
       size_t estimated_strength() const override;
 
    protected:
-      EC_PublicKey() : m_domain_encoding(EC_DOMPAR_ENC_EXPLICIT) {}
+      EC_PublicKey() : m_domain_params{}, m_public_key{}, m_domain_encoding(EC_DOMPAR_ENC_EXPLICIT)
+      {}
 
       EC_Group m_domain_params;
       PointGFp m_public_key;
diff --git a/src/lib/pubkey/if_algo/if_algo.cpp b/src/lib/pubkey/if_algo/if_algo.cpp
index a79cad116..e5f3ae20f 100644
--- a/src/lib/pubkey/if_algo/if_algo.cpp
+++ b/src/lib/pubkey/if_algo/if_algo.cpp
@@ -97,13 +97,11 @@ IF_Scheme_PrivateKey::IF_Scheme_PrivateKey(RandomNumberGenerator& rng,
                                            const BigInt& prime2,
                                            const BigInt& exp,
                                            const BigInt& d_exp,
-                                           const BigInt& mod)
+                                           const BigInt& mod) : 
+      m_d{ d_exp }, m_p{ prime1 }, m_q{ prime2 }, m_d1{}, m_d2{}, m_c{ inverse_mod( m_q, m_p ) }
    {
-   m_p = prime1;
-   m_q = prime2;
-   m_e = exp;
-   m_d = d_exp;
    m_n = mod.is_nonzero() ? mod : m_p * m_q;
+   m_e = exp;
 
    if(m_d == 0)
       {
@@ -116,7 +114,6 @@ IF_Scheme_PrivateKey::IF_Scheme_PrivateKey(RandomNumberGenerator& rng,
 
    m_d1 = m_d % (m_p - 1);
    m_d2 = m_d % (m_q - 1);
-   m_c = inverse_mod(m_q, m_p);
 
    load_check(rng);
    }
diff --git a/src/lib/pubkey/mce/gf2m_small_m.h b/src/lib/pubkey/mce/gf2m_small_m.h
index 6a8de4424..0b27a82e3 100644
--- a/src/lib/pubkey/mce/gf2m_small_m.h
+++ b/src/lib/pubkey/mce/gf2m_small_m.h
@@ -25,7 +25,7 @@ typedef u16bit gf2m;
 class BOTAN_DLL GF2m_Field
    {
    public:
-      GF2m_Field(size_t extdeg);
+      explicit GF2m_Field(size_t extdeg);
 
       gf2m gf_mul(gf2m x, gf2m y) const
          {
diff --git a/src/lib/pubkey/mce/mceliece.h b/src/lib/pubkey/mce/mceliece.h
index b9e54ec0e..311f0f253 100644
--- a/src/lib/pubkey/mce/mceliece.h
+++ b/src/lib/pubkey/mce/mceliece.h
@@ -21,7 +21,7 @@ namespace Botan {
 class BOTAN_DLL McEliece_PublicKey : public virtual Public_Key
    {
    public:
-      McEliece_PublicKey(const std::vector<byte>& key_bits);
+      explicit McEliece_PublicKey(const std::vector<byte>& key_bits);
 
       McEliece_PublicKey(std::vector<byte> const& pub_matrix, u32bit the_t, u32bit the_code_length) :
          m_public_matrix(pub_matrix),
@@ -90,7 +90,7 @@ class BOTAN_DLL McEliece_PrivateKey : public virtual McEliece_PublicKey,
       */
       McEliece_PrivateKey(RandomNumberGenerator& rng, size_t code_length, size_t t);
 
-      McEliece_PrivateKey(const secure_vector<byte>& key_bits);
+      explicit McEliece_PrivateKey(const secure_vector<byte>& key_bits);
 
       McEliece_PrivateKey(polyn_gf2m const& goppa_polyn,
                           std::vector<u32bit> const& parity_check_matrix_coeffs,
diff --git a/src/lib/pubkey/mce/polyn_gf2m.h b/src/lib/pubkey/mce/polyn_gf2m.h
index 938c1f553..62264e480 100644
--- a/src/lib/pubkey/mce/polyn_gf2m.h
+++ b/src/lib/pubkey/mce/polyn_gf2m.h
@@ -27,7 +27,7 @@ struct polyn_gf2m
       /**
       * create a zero polynomial:
       */
-      polyn_gf2m( std::shared_ptr<GF2m_Field> sp_field );
+      explicit polyn_gf2m( std::shared_ptr<GF2m_Field> sp_field );
 
       polyn_gf2m()
          :m_deg(-1)
diff --git a/src/lib/pubkey/nr/nr.cpp b/src/lib/pubkey/nr/nr.cpp
index 64e08a111..5e2cb1be5 100644
--- a/src/lib/pubkey/nr/nr.cpp
+++ b/src/lib/pubkey/nr/nr.cpp
@@ -144,13 +144,10 @@ class NR_Verification_Operation : public PK_Ops::Verification_with_EMSA
       typedef NR_PublicKey Key_Type;
       NR_Verification_Operation(const NR_PublicKey& nr, const std::string& emsa) :
          PK_Ops::Verification_with_EMSA(emsa),
-         m_q(nr.group_q()), m_y(nr.get_y())
-         {
-         m_powermod_g_p = Fixed_Base_Power_Mod(nr.group_g(), nr.group_p());
-         m_powermod_y_p = Fixed_Base_Power_Mod(m_y, nr.group_p());
-         m_mod_p = Modular_Reducer(nr.group_p());
-         m_mod_q = Modular_Reducer(nr.group_q());
-         }
+         m_q(nr.group_q()), m_y(nr.get_y()), m_powermod_g_p{Fixed_Base_Power_Mod(nr.group_g(), nr.group_p())},
+         m_powermod_y_p{Fixed_Base_Power_Mod(m_y, nr.group_p())}, m_mod_p{Modular_Reducer(nr.group_p())},
+         m_mod_q{Modular_Reducer(nr.group_q())}
+         {}
 
       size_t message_parts() const override { return 2; }
       size_t message_part_size() const override { return m_q.bytes(); }
diff --git a/src/lib/pubkey/pk_ops_impl.h b/src/lib/pubkey/pk_ops_impl.h
index bda3434bf..9be65cf21 100644
--- a/src/lib/pubkey/pk_ops_impl.h
+++ b/src/lib/pubkey/pk_ops_impl.h
@@ -23,7 +23,7 @@ class Encryption_with_EME : public Encryption
 
       ~Encryption_with_EME();
    protected:
-      Encryption_with_EME(const std::string& eme);
+      explicit Encryption_with_EME(const std::string& eme);
    private:
       virtual size_t max_raw_input_bits() const = 0;
 
@@ -41,7 +41,7 @@ class Decryption_with_EME : public Decryption
 
       ~Decryption_with_EME();
    protected:
-      Decryption_with_EME(const std::string& eme);
+      explicit Decryption_with_EME(const std::string& eme);
    private:
       virtual size_t max_raw_input_bits() const = 0;
       virtual secure_vector<byte> raw_decrypt(const byte msg[], size_t len) = 0;
@@ -59,7 +59,7 @@ class Verification_with_EMSA : public Verification
 
    protected:
 
-      Verification_with_EMSA(const std::string& emsa);
+      explicit Verification_with_EMSA(const std::string& emsa);
       ~Verification_with_EMSA();
 
       /**
@@ -105,7 +105,7 @@ class Signature_with_EMSA : public Signature
 
       secure_vector<byte> sign(RandomNumberGenerator& rng) override;
    protected:
-      Signature_with_EMSA(const std::string& emsa);
+      explicit Signature_with_EMSA(const std::string& emsa);
       ~Signature_with_EMSA();
    private:
 
@@ -132,7 +132,7 @@ class Key_Agreement_with_KDF : public Key_Agreement
                                 const byte salt[], size_t salt_len) override;
 
    protected:
-      Key_Agreement_with_KDF(const std::string& kdf);
+      explicit Key_Agreement_with_KDF(const std::string& kdf);
       ~Key_Agreement_with_KDF();
    private:
       virtual secure_vector<byte> raw_agree(const byte w[], size_t w_len) = 0;
@@ -154,7 +154,7 @@ class KEM_Encryption_with_KDF : public KEM_Encryption
                                    secure_vector<byte>& raw_shared_key,
                                    Botan::RandomNumberGenerator& rng) = 0;
 
-      KEM_Encryption_with_KDF(const std::string& kdf);
+      explicit KEM_Encryption_with_KDF(const std::string& kdf);
       ~KEM_Encryption_with_KDF();
    private:
       std::unique_ptr<KDF> m_kdf;
@@ -173,7 +173,7 @@ class KEM_Decryption_with_KDF : public KEM_Decryption
       virtual secure_vector<byte>
       raw_kem_decrypt(const byte encap_key[], size_t len) = 0;
 
-      KEM_Decryption_with_KDF(const std::string& kdf);
+      explicit KEM_Decryption_with_KDF(const std::string& kdf);
       ~KEM_Decryption_with_KDF();
    private:
       std::unique_ptr<KDF> m_kdf;
diff --git a/src/lib/pubkey/pkcs8.h b/src/lib/pubkey/pkcs8.h
index 9dc5265c7..791a612df 100644
--- a/src/lib/pubkey/pkcs8.h
+++ b/src/lib/pubkey/pkcs8.h
@@ -19,7 +19,7 @@ namespace Botan {
 */
 struct BOTAN_DLL PKCS8_Exception : public Decoding_Error
    {
-   PKCS8_Exception(const std::string& error) :
+   explicit PKCS8_Exception(const std::string& error) :
       Decoding_Error("PKCS #8: " + error) {}
    };
 
diff --git a/src/lib/pubkey/rsa/rsa.cpp b/src/lib/pubkey/rsa/rsa.cpp
index 18a694754..eb9fc2892 100644
--- a/src/lib/pubkey/rsa/rsa.cpp
+++ b/src/lib/pubkey/rsa/rsa.cpp
@@ -71,7 +71,7 @@ class RSA_Private_Operation
    protected:
       size_t get_max_input_bits() const { return (m_n.bits() - 1); }
 
-      RSA_Private_Operation(const RSA_PrivateKey& rsa) :
+      explicit RSA_Private_Operation(const RSA_PrivateKey& rsa) :
          m_n(rsa.get_n()),
          m_q(rsa.get_q()),
          m_c(rsa.get_c()),
@@ -190,7 +190,7 @@ class RSA_KEM_Decryption_Operation : public PK_Ops::KEM_Decryption_with_KDF,
 class RSA_Public_Operation
    {
    public:
-      RSA_Public_Operation(const RSA_PublicKey& rsa) :
+      explicit RSA_Public_Operation(const RSA_PublicKey& rsa) :
          m_n(rsa.get_n()), m_powermod_e_n(rsa.get_e(), rsa.get_n())
          {}
 
diff --git a/src/lib/rng/rng.h b/src/lib/rng/rng.h
index a01212359..2e29a713c 100644
--- a/src/lib/rng/rng.h
+++ b/src/lib/rng/rng.h
@@ -199,7 +199,7 @@ class BOTAN_DLL Serialized_RNG : public RandomNumberGenerator
          }
 
       Serialized_RNG() : m_rng(RandomNumberGenerator::make_rng()) {}
-      Serialized_RNG(RandomNumberGenerator* rng) : m_rng(rng) {}
+      explicit Serialized_RNG(RandomNumberGenerator* rng) : m_rng(rng) {}
    private:
       mutable std::mutex m_mutex;
       std::unique_ptr<RandomNumberGenerator> m_rng;
diff --git a/src/lib/stream/ctr/ctr.h b/src/lib/stream/ctr/ctr.h
index dc05fa596..8e931605c 100644
--- a/src/lib/stream/ctr/ctr.h
+++ b/src/lib/stream/ctr/ctr.h
@@ -43,7 +43,7 @@ class BOTAN_DLL CTR_BE final : public StreamCipher
       /**
       * @param cipher the underlying block cipher to use
       */
-      CTR_BE(BlockCipher* cipher);
+      explicit CTR_BE(BlockCipher* cipher);
    private:
       void key_schedule(const byte key[], size_t key_len) override;
       void increment_counter();
diff --git a/src/lib/stream/ofb/ofb.h b/src/lib/stream/ofb/ofb.h
index 4775c5575..fecd47d9d 100644
--- a/src/lib/stream/ofb/ofb.h
+++ b/src/lib/stream/ofb/ofb.h
@@ -43,7 +43,7 @@ class BOTAN_DLL OFB final : public StreamCipher
       /**
       * @param cipher the underlying block cipher to use
       */
-      OFB(BlockCipher* cipher);
+      explicit OFB(BlockCipher* cipher);
    private:
       void key_schedule(const byte key[], size_t key_len) override;
 
diff --git a/src/lib/stream/rc4/rc4.h b/src/lib/stream/rc4/rc4.h
index db1726a18..f166a2772 100644
--- a/src/lib/stream/rc4/rc4.h
+++ b/src/lib/stream/rc4/rc4.h
@@ -36,7 +36,7 @@ class BOTAN_DLL RC4 final : public StreamCipher
       /**
       * @param skip skip this many initial bytes in the keystream
       */
-      RC4(size_t skip = 0);
+      explicit RC4(size_t skip = 0);
 
       ~RC4() { clear(); }
    private:
diff --git a/src/lib/stream/stream_cipher.cpp b/src/lib/stream/stream_cipher.cpp
index 060e65d86..03ef5e329 100644
--- a/src/lib/stream/stream_cipher.cpp
+++ b/src/lib/stream/stream_cipher.cpp
@@ -33,7 +33,7 @@ namespace Botan {
 std::unique_ptr<StreamCipher> StreamCipher::create(const std::string& algo_spec,
                                                    const std::string& provider)
    {
-   return std::unique_ptr<StreamCipher>(make_a<StreamCipher>(algo_spec, provider));
+   return std::unique_ptr<StreamCipher>(make_a<StreamCipher>(Botan::StreamCipher::Spec(algo_spec), provider));
    }
 
 std::vector<std::string> StreamCipher::providers(const std::string& algo_spec)
diff --git a/src/lib/tls/msg_finished.cpp b/src/lib/tls/msg_finished.cpp
index b837172b6..2d6b11995 100644
--- a/src/lib/tls/msg_finished.cpp
+++ b/src/lib/tls/msg_finished.cpp
@@ -48,9 +48,8 @@ std::vector<byte> finished_compute_verify(const Handshake_State& state,
 */
 Finished::Finished(Handshake_IO& io,
                    Handshake_State& state,
-                   Connection_Side side)
+                   Connection_Side side) : m_verification_data(finished_compute_verify( state, side ))
    {
-   m_verification_data = finished_compute_verify(state, side);
    state.hash().update(io.send(*this));
    }
 
@@ -65,10 +64,8 @@ std::vector<byte> Finished::serialize() const
 /*
 * Deserialize a Finished message
 */
-Finished::Finished(const std::vector<byte>& buf)
-   {
-   m_verification_data = buf;
-   }
+Finished::Finished(const std::vector<byte>& buf) : m_verification_data(buf)
+   {}
 
 /*
 * Verify a Finished message
diff --git a/src/lib/tls/msg_server_hello.cpp b/src/lib/tls/msg_server_hello.cpp
index f9962a8ee..f8d0c63c7 100644
--- a/src/lib/tls/msg_server_hello.cpp
+++ b/src/lib/tls/msg_server_hello.cpp
@@ -28,7 +28,7 @@ Server_Hello::Server_Hello(Handshake_IO& io,
                            u16bit ciphersuite,
                            byte compression,
                            bool offer_session_ticket,
-                           const std::string next_protocol) :
+                           const std::string& next_protocol) :
    m_version(new_session_version),
    m_session_id(new_session_id),
    m_random(make_hello_random(rng, policy)),
diff --git a/src/lib/tls/msg_server_kex.cpp b/src/lib/tls/msg_server_kex.cpp
index fcff7349e..7389cb35b 100644
--- a/src/lib/tls/msg_server_kex.cpp
+++ b/src/lib/tls/msg_server_kex.cpp
@@ -48,7 +48,7 @@ Server_Key_Exchange::Server_Key_Exchange(Handshake_IO& io,
 
    if(kex_algo == "DH" || kex_algo == "DHE_PSK")
       {
-      std::unique_ptr<DH_PrivateKey> dh(new DH_PrivateKey(rng, policy.dh_group()));
+      std::unique_ptr<DH_PrivateKey> dh(new DH_PrivateKey(rng, DL_Group(policy.dh_group())));
 
       append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_p()), 2);
       append_tls_length_value(m_params, BigInt::encode(dh->get_domain().get_g()), 2);
diff --git a/src/lib/tls/tls_alert.h b/src/lib/tls/tls_alert.h
index 2c82514a3..1184c6260 100644
--- a/src/lib/tls/tls_alert.h
+++ b/src/lib/tls/tls_alert.h
@@ -92,7 +92,7 @@ class BOTAN_DLL Alert
       * Deserialize an Alert message
       * @param buf the serialized alert
       */
-      Alert(const secure_vector<byte>& buf);
+      explicit Alert(const secure_vector<byte>& buf);
 
       /**
       * Create a new Alert
diff --git a/src/lib/tls/tls_blocking.cpp b/src/lib/tls/tls_blocking.cpp
index f88b7896c..a1867b6b5 100644
--- a/src/lib/tls/tls_blocking.cpp
+++ b/src/lib/tls/tls_blocking.cpp
@@ -20,7 +20,7 @@ Blocking_Client::Blocking_Client(read_fn reader,
                                  const Policy& policy,
                                  RandomNumberGenerator& rng,
                                  const Server_Information& server_info,
-                                 const Protocol_Version offer_version,
+                                 const Protocol_Version& offer_version,
                                  const std::vector<std::string>& next) :
    m_read(reader),
    m_channel(writer,
@@ -42,7 +42,7 @@ bool Blocking_Client::handshake_cb(const Session& session)
    return this->handshake_complete(session);
    }
 
-void Blocking_Client::alert_cb(const Alert alert, const byte[], size_t)
+void Blocking_Client::alert_cb(const Alert& alert, const byte[], size_t)
    {
    this->alert_notification(alert);
    }
diff --git a/src/lib/tls/tls_blocking.h b/src/lib/tls/tls_blocking.h
index 89421f5f5..00e65cbaf 100644
--- a/src/lib/tls/tls_blocking.h
+++ b/src/lib/tls/tls_blocking.h
@@ -39,7 +39,7 @@ class BOTAN_DLL Blocking_Client
                       const Policy& policy,
                       RandomNumberGenerator& rng,
                       const Server_Information& server_info = Server_Information(),
-                      const Protocol_Version offer_version = Protocol_Version::latest_tls_version(),
+                      const Protocol_Version& offer_version = Protocol_Version::latest_tls_version(),
                       const std::vector<std::string>& next_protos = {});
 
       /**
@@ -89,7 +89,7 @@ class BOTAN_DLL Blocking_Client
 
       void data_cb(const byte data[], size_t data_len);
 
-      void alert_cb(const Alert alert, const byte data[], size_t data_len);
+      void alert_cb(const Alert& alert, const byte data[], size_t data_len);
 
       read_fn m_read;
       TLS::Client m_channel;
diff --git a/src/lib/tls/tls_client.cpp b/src/lib/tls/tls_client.cpp
index 368e4569e..3a219ccff 100644
--- a/src/lib/tls/tls_client.cpp
+++ b/src/lib/tls/tls_client.cpp
@@ -51,7 +51,7 @@ Client::Client(output_fn output_fn,
                const Policy& policy,
                RandomNumberGenerator& rng,
                const Server_Information& info,
-               const Protocol_Version offer_version,
+               const Protocol_Version& offer_version,
                const std::vector<std::string>& next_protos,
                size_t io_buf_sz) :
    Channel(output_fn, proc_cb, alert_cb, handshake_cb, Channel::handshake_msg_cb(),
@@ -75,7 +75,7 @@ Client::Client(output_fn output_fn,
                const Policy& policy,
                RandomNumberGenerator& rng,
                const Server_Information& info,
-               const Protocol_Version offer_version,
+               const Protocol_Version& offer_version,
                const std::vector<std::string>& next_protos) :
    Channel(output_fn, proc_cb, alert_cb, handshake_cb, hs_msg_cb,
            session_manager, rng, policy, offer_version.is_datagram_protocol()),
diff --git a/src/lib/tls/tls_client.h b/src/lib/tls/tls_client.h
index d17ea74d0..45a741878 100644
--- a/src/lib/tls/tls_client.h
+++ b/src/lib/tls/tls_client.h
@@ -62,7 +62,7 @@ class BOTAN_DLL Client final : public Channel
              const Policy& policy,
              RandomNumberGenerator& rng,
              const Server_Information& server_info = Server_Information(),
-             const Protocol_Version offer_version = Protocol_Version::latest_tls_version(),
+             const Protocol_Version& offer_version = Protocol_Version::latest_tls_version(),
              const std::vector<std::string>& next_protocols = {},
              size_t reserved_io_buffer_size = 16*1024
          );
@@ -77,7 +77,7 @@ class BOTAN_DLL Client final : public Channel
              const Policy& policy,
              RandomNumberGenerator& rng,
              const Server_Information& server_info = Server_Information(),
-             const Protocol_Version offer_version = Protocol_Version::latest_tls_version(),
+             const Protocol_Version& offer_version = Protocol_Version::latest_tls_version(),
              const std::vector<std::string>& next_protocols = {}
          );
 
diff --git a/src/lib/tls/tls_exceptn.h b/src/lib/tls/tls_exceptn.h
index 509226094..2ed5b685c 100644
--- a/src/lib/tls/tls_exceptn.h
+++ b/src/lib/tls/tls_exceptn.h
@@ -36,7 +36,7 @@ class BOTAN_DLL TLS_Exception : public Exception
 */
 struct BOTAN_DLL Unexpected_Message : public TLS_Exception
    {
-   Unexpected_Message(const std::string& err) :
+   explicit Unexpected_Message(const std::string& err) :
       TLS_Exception(Alert::UNEXPECTED_MESSAGE, err) {}
    };
 
diff --git a/src/lib/tls/tls_extensions.cpp b/src/lib/tls/tls_extensions.cpp
index 35c39ddab..4acf9a6fe 100644
--- a/src/lib/tls/tls_extensions.cpp
+++ b/src/lib/tls/tls_extensions.cpp
@@ -180,10 +180,8 @@ std::vector<byte> Server_Name_Indicator::serialize() const
 #if defined(BOTAN_HAS_SRP6)
 
 SRP_Identifier::SRP_Identifier(TLS_Data_Reader& reader,
-                               u16bit extension_size)
+                               u16bit extension_size) : m_srp_identifier(reader.get_string(1, 1, 255))
    {
-   m_srp_identifier = reader.get_string(1, 1, 255);
-
    if(m_srp_identifier.size() + 1 != extension_size)
       throw Decoding_Error("Bad encoding for SRP identifier extension");
    }
@@ -203,10 +201,8 @@ std::vector<byte> SRP_Identifier::serialize() const
 #endif
 
 Renegotiation_Extension::Renegotiation_Extension(TLS_Data_Reader& reader,
-                                                 u16bit extension_size)
+                                                 u16bit extension_size) : m_reneg_data(reader.get_range<byte>(1, 0, 255))
    {
-   m_reneg_data = reader.get_range<byte>(1, 0, 255);
-
    if(m_reneg_data.size() + 1 != extension_size)
       throw Decoding_Error("Bad encoding for secure renegotiation extn");
    }
@@ -516,16 +512,12 @@ Signature_Algorithms::Signature_Algorithms(TLS_Data_Reader& reader,
    }
 
 Session_Ticket::Session_Ticket(TLS_Data_Reader& reader,
-                               u16bit extension_size)
-   {
-   m_ticket = reader.get_elem<byte, std::vector<byte> >(extension_size);
-   }
+                               u16bit extension_size) : m_ticket(reader.get_elem<byte, std::vector<byte>>(extension_size))
+   {}
 
 SRTP_Protection_Profiles::SRTP_Protection_Profiles(TLS_Data_Reader& reader,
-                                                   u16bit extension_size)
+                                                   u16bit extension_size) : m_pp(reader.get_range<u16bit>(2, 0, 65535))
    {
-   m_pp = reader.get_range<u16bit>(2, 0, 65535);
-
    const std::vector<byte> mki = reader.get_range<byte>(1, 0, 255);
 
    if(m_pp.size() * 2 + mki.size() + 3 != extension_size)
diff --git a/src/lib/tls/tls_extensions.h b/src/lib/tls/tls_extensions.h
index 5a8aff9de..a5aac0020 100644
--- a/src/lib/tls/tls_extensions.h
+++ b/src/lib/tls/tls_extensions.h
@@ -79,7 +79,7 @@ class Server_Name_Indicator final : public Extension
 
       Handshake_Extension_Type type() const override { return static_type(); }
 
-      Server_Name_Indicator(const std::string& host_name) :
+      explicit Server_Name_Indicator(const std::string& host_name) :
          m_sni_host_name(host_name) {}
 
       Server_Name_Indicator(TLS_Data_Reader& reader,
@@ -106,7 +106,7 @@ class SRP_Identifier final : public Extension
 
       Handshake_Extension_Type type() const override { return static_type(); }
 
-      SRP_Identifier(const std::string& identifier) :
+      explicit SRP_Identifier(const std::string& identifier) :
          m_srp_identifier(identifier) {}
 
       SRP_Identifier(TLS_Data_Reader& reader,
@@ -135,7 +135,7 @@ class Renegotiation_Extension final : public Extension
 
       Renegotiation_Extension() {}
 
-      Renegotiation_Extension(const std::vector<byte>& bits) :
+      explicit Renegotiation_Extension(const std::vector<byte>& bits) :
          m_reneg_data(bits) {}
 
       Renegotiation_Extension(TLS_Data_Reader& reader,
@@ -168,13 +168,13 @@ class Application_Layer_Protocol_Notification final : public Extension
       /**
       * Single protocol, used by server
       */
-      Application_Layer_Protocol_Notification(const std::string& protocol) :
+      explicit Application_Layer_Protocol_Notification(const std::string& protocol) :
          m_protocols(1, protocol) {}
 
       /**
       * List of protocols, used by client
       */
-      Application_Layer_Protocol_Notification(const std::vector<std::string>& protocols) :
+      explicit Application_Layer_Protocol_Notification(const std::vector<std::string>& protocols) :
          m_protocols(protocols) {}
 
       Application_Layer_Protocol_Notification(TLS_Data_Reader& reader,
@@ -211,7 +211,7 @@ class Session_Ticket final : public Extension
       /**
       * Extension with ticket, used by client
       */
-      Session_Ticket(const std::vector<byte>& session_ticket) :
+      explicit Session_Ticket(const std::vector<byte>& session_ticket) :
          m_ticket(session_ticket) {}
 
       /**
@@ -244,7 +244,7 @@ class Supported_Elliptic_Curves final : public Extension
 
       std::vector<byte> serialize() const override;
 
-      Supported_Elliptic_Curves(const std::vector<std::string>& curves) :
+      explicit Supported_Elliptic_Curves(const std::vector<std::string>& curves) :
          m_curves(curves) {}
 
       Supported_Elliptic_Curves(TLS_Data_Reader& reader,
@@ -285,7 +285,7 @@ class Signature_Algorithms final : public Extension
       Signature_Algorithms(const std::vector<std::string>& hashes,
                            const std::vector<std::string>& sig_algos);
 
-      Signature_Algorithms(const std::vector<std::pair<std::string, std::string> >& algos) :
+      explicit Signature_Algorithms(const std::vector<std::pair<std::string, std::string> >& algos) :
          m_supported_algos(algos) {}
 
       Signature_Algorithms(TLS_Data_Reader& reader,
@@ -311,9 +311,9 @@ class SRTP_Protection_Profiles final : public Extension
 
       bool empty() const override { return m_pp.empty(); }
 
-      SRTP_Protection_Profiles(const std::vector<u16bit>& pp) : m_pp(pp) {}
+      explicit SRTP_Protection_Profiles(const std::vector<u16bit>& pp) : m_pp(pp) {}
 
-      SRTP_Protection_Profiles(u16bit pp) : m_pp(1, pp) {}
+      explicit SRTP_Protection_Profiles(u16bit pp) : m_pp(1, pp) {}
 
       SRTP_Protection_Profiles(TLS_Data_Reader& reader, u16bit extension_size);
    private:
@@ -377,7 +377,7 @@ class Extensions
 
       Extensions() {}
 
-      Extensions(TLS_Data_Reader& reader) { deserialize(reader); }
+      explicit Extensions(TLS_Data_Reader& reader) { deserialize(reader); }
 
    private:
       Extensions(const Extensions&) {}
diff --git a/src/lib/tls/tls_handshake_io.h b/src/lib/tls/tls_handshake_io.h
index f2bb2ac71..601ac41d9 100644
--- a/src/lib/tls/tls_handshake_io.h
+++ b/src/lib/tls/tls_handshake_io.h
@@ -67,7 +67,7 @@ class Stream_Handshake_IO final : public Handshake_IO
    public:
       typedef std::function<void (byte, const std::vector<byte>&)> writer_fn;
 
-      Stream_Handshake_IO(writer_fn writer) : m_send_hs(writer) {}
+      explicit Stream_Handshake_IO(writer_fn writer) : m_send_hs(writer) {}
 
       Protocol_Version initial_record_version() const override;
 
diff --git a/src/lib/tls/tls_messages.h b/src/lib/tls/tls_messages.h
index c648df720..00033826f 100644
--- a/src/lib/tls/tls_messages.h
+++ b/src/lib/tls/tls_messages.h
@@ -46,7 +46,7 @@ class Hello_Verify_Request final : public Handshake_Message
 
       std::vector<byte> cookie() const { return m_cookie; }
 
-      Hello_Verify_Request(const std::vector<byte>& buf);
+      explicit Hello_Verify_Request(const std::vector<byte>& buf);
 
       Hello_Verify_Request(const std::vector<byte>& client_hello_bits,
                            const std::string& client_identity,
@@ -178,7 +178,7 @@ class Client_Hello final : public Handshake_Message
                    const Session& resumed_session,
                    const std::vector<std::string>& next_protocols);
 
-      Client_Hello(const std::vector<byte>& buf);
+      explicit Client_Hello(const std::vector<byte>& buf);
 
    private:
       std::vector<byte> serialize() const override;
@@ -267,7 +267,7 @@ class Server_Hello final : public Handshake_Message
                    u16bit ciphersuite,
                    byte compression,
                    bool offer_session_ticket,
-                   const std::string next_protocol);
+                   const std::string& next_protocol);
 
       Server_Hello(Handshake_IO& io,
                    Handshake_Hash& hash,
@@ -279,7 +279,7 @@ class Server_Hello final : public Handshake_Message
                    bool offer_session_ticket,
                    const std::string& next_protocol);
 
-      Server_Hello(const std::vector<byte>& buf);
+      explicit Server_Hello(const std::vector<byte>& buf);
    private:
       std::vector<byte> serialize() const override;
 
@@ -341,7 +341,7 @@ class Certificate final : public Handshake_Message
                   Handshake_Hash& hash,
                   const std::vector<X509_Certificate>& certs);
 
-      Certificate(const std::vector<byte>& buf);
+      explicit Certificate(const std::vector<byte>& buf);
    private:
       std::vector<byte> serialize() const override;
 
@@ -431,7 +431,7 @@ class Finished final : public Handshake_Message
                Handshake_State& state,
                Connection_Side side);
 
-      Finished(const std::vector<byte>& buf);
+      explicit Finished(const std::vector<byte>& buf);
    private:
       std::vector<byte> serialize() const override;
 
@@ -446,8 +446,8 @@ class Hello_Request final : public Handshake_Message
    public:
       Handshake_Type type() const override { return HELLO_REQUEST; }
 
-      Hello_Request(Handshake_IO& io);
-      Hello_Request(const std::vector<byte>& buf);
+      explicit Hello_Request(Handshake_IO& io);
+      explicit Hello_Request(const std::vector<byte>& buf);
    private:
       std::vector<byte> serialize() const override;
    };
@@ -514,7 +514,7 @@ class Server_Hello_Done final : public Handshake_Message
       Handshake_Type type() const override { return SERVER_HELLO_DONE; }
 
       Server_Hello_Done(Handshake_IO& io, Handshake_Hash& hash);
-      Server_Hello_Done(const std::vector<byte>& buf);
+      explicit Server_Hello_Done(const std::vector<byte>& buf);
    private:
       std::vector<byte> serialize() const override;
    };
@@ -538,7 +538,7 @@ class New_Session_Ticket final : public Handshake_Message
       New_Session_Ticket(Handshake_IO& io,
                          Handshake_Hash& hash);
 
-      New_Session_Ticket(const std::vector<byte>& buf);
+      explicit New_Session_Ticket(const std::vector<byte>& buf);
    private:
       std::vector<byte> serialize() const override;
 
diff --git a/src/lib/tls/tls_policy.h b/src/lib/tls/tls_policy.h
index c1f40df17..6e4b442c8 100644
--- a/src/lib/tls/tls_policy.h
+++ b/src/lib/tls/tls_policy.h
@@ -300,16 +300,14 @@ class BOTAN_DLL Text_Policy : public Policy
 
       void set(const std::string& k, const std::string& v) { m_kv[k] = v; }
 
-      Text_Policy(const std::string& s)
+      explicit Text_Policy(const std::string& s)
          {
          std::istringstream iss(s);
          m_kv = read_cfg(iss);
          }
 
-      Text_Policy(std::istream& in)
-         {
-         m_kv = read_cfg(in);
-         }
+      explicit Text_Policy(std::istream& in) : m_kv(read_cfg(in))
+         {}
 
    private:
 
diff --git a/src/lib/tls/tls_session.h b/src/lib/tls/tls_session.h
index 0e22037f6..8ca646cf2 100644
--- a/src/lib/tls/tls_session.h
+++ b/src/lib/tls/tls_session.h
@@ -65,7 +65,7 @@ class BOTAN_DLL Session
       /**
       * Load a session from PEM representation (created by PEM_encode)
       */
-      Session(const std::string& pem);
+      explicit Session(const std::string& pem);
 
       /**
       * Encode this session data for storage
diff --git a/src/lib/utils/data_src.h b/src/lib/utils/data_src.h
index 0a6ce0a8c..6a100ce63 100644
--- a/src/lib/utils/data_src.h
+++ b/src/lib/utils/data_src.h
@@ -108,7 +108,7 @@ class BOTAN_DLL DataSource_Memory : public DataSource
       * Construct a memory source that reads from a string
       * @param in the string to read from
       */
-      DataSource_Memory(const std::string& in);
+      explicit DataSource_Memory(const std::string& in);
 
       /**
       * Construct a memory source that reads from a byte array
@@ -122,14 +122,14 @@ class BOTAN_DLL DataSource_Memory : public DataSource
       * Construct a memory source that reads from a secure_vector
       * @param in the MemoryRegion to read from
       */
-      DataSource_Memory(const secure_vector<byte>& in) :
+      explicit DataSource_Memory(const secure_vector<byte>& in) :
          m_source(in), m_offset(0) {}
 
       /**
       * Construct a memory source that reads from a std::vector
       * @param in the MemoryRegion to read from
       */
-      DataSource_Memory(const std::vector<byte>& in) :
+      explicit DataSource_Memory(const std::vector<byte>& in) :
          m_source(in.begin(), in.end()), m_offset(0) {}
 
       size_t get_bytes_read() const override { return m_offset; }
diff --git a/src/lib/utils/database.h b/src/lib/utils/database.h
index 4d8b90d0c..4cc0989b1 100644
--- a/src/lib/utils/database.h
+++ b/src/lib/utils/database.h
@@ -23,7 +23,7 @@ class BOTAN_DLL SQL_Database
       class BOTAN_DLL SQL_DB_Error : public Exception
          {
          public:
-            SQL_DB_Error(const std::string& what) : Exception("SQL database", what) {}
+            explicit SQL_DB_Error(const std::string& what) : Exception("SQL database", what) {}
          };
 
       class BOTAN_DLL Statement
diff --git a/src/lib/utils/donna128.h b/src/lib/utils/donna128.h
index c72ccb55c..c2a3e0d2e 100644
--- a/src/lib/utils/donna128.h
+++ b/src/lib/utils/donna128.h
@@ -104,8 +104,8 @@ inline u64bit carry_shift(const donna128& a, size_t shift)
    return (a >> shift).lo();
    }
 
-inline u64bit combine_lower(const donna128 a, size_t s1,
-                            const donna128 b, size_t s2)
+inline u64bit combine_lower(const donna128& a, size_t s1,
+                            const donna128& b, size_t s2)
    {
    donna128 z = (a >> s1) | (b << s2);
    return z.lo();
diff --git a/src/lib/utils/exceptn.h b/src/lib/utils/exceptn.h
index 1e9cd68d5..b6797f0f6 100644
--- a/src/lib/utils/exceptn.h
+++ b/src/lib/utils/exceptn.h
@@ -21,7 +21,7 @@ namespace Botan {
 class BOTAN_DLL Exception : public std::exception
    {
    public:
-      Exception(const std::string& msg) : m_msg(msg) {}
+      explicit Exception(const std::string& msg) : m_msg(msg) {}
       Exception(const char* prefix, const std::string& msg) : m_msg(std::string(prefix) + " " + msg) {}
       const char* what() const BOTAN_NOEXCEPT override { return m_msg.c_str(); }
    private:
@@ -34,7 +34,7 @@ class BOTAN_DLL Exception : public std::exception
 class BOTAN_DLL Invalid_Argument : public Exception
    {
    public:
-      Invalid_Argument(const std::string& msg) :
+      explicit Invalid_Argument(const std::string& msg) :
          Exception("Invalid argument", msg) {}
    };
 
@@ -46,7 +46,7 @@ class BOTAN_DLL Invalid_Argument : public Exception
 */
 struct BOTAN_DLL Unsupported_Argument : public Invalid_Argument
    {
-   Unsupported_Argument(const std::string& msg) : Invalid_Argument(msg) {}
+   explicit Unsupported_Argument(const std::string& msg) : Invalid_Argument(msg) {}
    };
 
 /**
@@ -54,7 +54,7 @@ struct BOTAN_DLL Unsupported_Argument : public Invalid_Argument
 */
 struct BOTAN_DLL Invalid_State : public Exception
    {
-   Invalid_State(const std::string& err) :
+   explicit Invalid_State(const std::string& err) :
       Exception(err)
       {}
    };
@@ -64,7 +64,7 @@ struct BOTAN_DLL Invalid_State : public Exception
 */
 struct BOTAN_DLL Lookup_Error : public Exception
    {
-   Lookup_Error(const std::string& err) :
+   explicit Lookup_Error(const std::string& err) :
       Exception(err)
       {}
    };
@@ -74,7 +74,7 @@ struct BOTAN_DLL Lookup_Error : public Exception
 */
 struct BOTAN_DLL Internal_Error : public Exception
    {
-   Internal_Error(const std::string& err) :
+   explicit Internal_Error(const std::string& err) :
       Exception("Internal error: " + err)
       {}
    };
@@ -106,7 +106,7 @@ struct BOTAN_DLL Invalid_IV_Length : public Invalid_Argument
 */
 struct BOTAN_DLL PRNG_Unseeded : public Invalid_State
    {
-   PRNG_Unseeded(const std::string& algo) :
+   explicit PRNG_Unseeded(const std::string& algo) :
       Invalid_State("PRNG not seeded: " + algo)
       {}
    };
@@ -116,7 +116,7 @@ struct BOTAN_DLL PRNG_Unseeded : public Invalid_State
 */
 struct BOTAN_DLL Policy_Violation : public Invalid_State
    {
-   Policy_Violation(const std::string& err) :
+   explicit Policy_Violation(const std::string& err) :
       Invalid_State("Policy violation: " + err)
       {}
    };
@@ -126,7 +126,7 @@ struct BOTAN_DLL Policy_Violation : public Invalid_State
 */
 struct BOTAN_DLL Algorithm_Not_Found : public Lookup_Error
    {
-   Algorithm_Not_Found(const std::string& name) :
+   explicit Algorithm_Not_Found(const std::string& name) :
       Lookup_Error("Could not find any algorithm named \"" + name + "\"")
       {}
    };
@@ -136,7 +136,7 @@ struct BOTAN_DLL Algorithm_Not_Found : public Lookup_Error
 */
 struct BOTAN_DLL No_Provider_Found : public Exception
    {
-   No_Provider_Found(const std::string& name) :
+   explicit No_Provider_Found(const std::string& name) :
       Exception("Could not find any provider for algorithm named \"" + name + "\"")
       {}
    };
@@ -146,7 +146,7 @@ struct BOTAN_DLL No_Provider_Found : public Exception
 */
 struct BOTAN_DLL Invalid_Algorithm_Name : public Invalid_Argument
    {
-   Invalid_Algorithm_Name(const std::string& name):
+   explicit Invalid_Algorithm_Name(const std::string& name):
       Invalid_Argument("Invalid algorithm name: " + name)
       {}
    };
@@ -156,7 +156,7 @@ struct BOTAN_DLL Invalid_Algorithm_Name : public Invalid_Argument
 */
 struct BOTAN_DLL Encoding_Error : public Invalid_Argument
    {
-   Encoding_Error(const std::string& name) :
+   explicit Encoding_Error(const std::string& name) :
       Invalid_Argument("Encoding error: " + name) {}
    };
 
@@ -165,7 +165,7 @@ struct BOTAN_DLL Encoding_Error : public Invalid_Argument
 */
 struct BOTAN_DLL Decoding_Error : public Invalid_Argument
    {
-   Decoding_Error(const std::string& name) :
+   explicit Decoding_Error(const std::string& name) :
       Invalid_Argument("Decoding error: " + name) {}
    };
 
@@ -174,7 +174,7 @@ struct BOTAN_DLL Decoding_Error : public Invalid_Argument
 */
 struct BOTAN_DLL Integrity_Failure : public Exception
    {
-   Integrity_Failure(const std::string& msg) :
+   explicit Integrity_Failure(const std::string& msg) :
       Exception("Integrity failure: " + msg) {}
    };
 
@@ -183,7 +183,7 @@ struct BOTAN_DLL Integrity_Failure : public Exception
 */
 struct BOTAN_DLL Invalid_OID : public Decoding_Error
    {
-   Invalid_OID(const std::string& oid) :
+   explicit Invalid_OID(const std::string& oid) :
       Decoding_Error("Invalid ASN.1 OID: " + oid) {}
    };
 
@@ -192,7 +192,7 @@ struct BOTAN_DLL Invalid_OID : public Decoding_Error
 */
 struct BOTAN_DLL Stream_IO_Error : public Exception
    {
-   Stream_IO_Error(const std::string& err) :
+   explicit Stream_IO_Error(const std::string& err) :
       Exception("I/O error: " + err)
       {}
    };
@@ -210,7 +210,7 @@ struct BOTAN_DLL No_Filesystem_Access : public Exception
 */
 struct BOTAN_DLL Self_Test_Failure : public Internal_Error
    {
-   Self_Test_Failure(const std::string& err) :
+   explicit Self_Test_Failure(const std::string& err) :
       Internal_Error("Self test failed: " + err)
       {}
    };
diff --git a/src/lib/utils/os_utils.cpp b/src/lib/utils/os_utils.cpp
index bd87ca2ed..8fa099bc6 100644
--- a/src/lib/utils/os_utils.cpp
+++ b/src/lib/utils/os_utils.cpp
@@ -30,8 +30,8 @@ uint32_t get_process_id()
    {
 #if defined(BOTAN_TARGET_OS_IS_UNIX)
    return ::getpid();
-#elif defined(BOTAN_TARGET_OS_IS_WIDOWS)
-   return ::GetProcessId();
+#elif defined(BOTAN_TARGET_OS_IS_WINDOWS)
+   return ::GetCurrentProcessId();
 #else
    return 0;
 #endif
diff --git a/src/lib/utils/semaphore.h b/src/lib/utils/semaphore.h
index 3495043e5..994a15f21 100644
--- a/src/lib/utils/semaphore.h
+++ b/src/lib/utils/semaphore.h
@@ -16,7 +16,7 @@ namespace Botan {
 class Semaphore
    {
    public:
-      Semaphore(int value = 0) : m_value(value), m_wakeups(0) {}
+      explicit Semaphore(int value = 0) : m_value(value), m_wakeups(0) {}
 
       void acquire();
 
diff --git a/src/lib/utils/simd/simd_sse2/simd_sse2.h b/src/lib/utils/simd/simd_sse2/simd_sse2.h
index 1757b5976..551e9189c 100644
--- a/src/lib/utils/simd/simd_sse2/simd_sse2.h
+++ b/src/lib/utils/simd/simd_sse2/simd_sse2.h
@@ -18,7 +18,7 @@ namespace Botan {
 class SIMD_SSE2
    {
    public:
-      SIMD_SSE2(const u32bit B[4])
+      explicit SIMD_SSE2(const u32bit B[4])
          {
          m_reg = _mm_loadu_si128(reinterpret_cast<const __m128i*>(B));
          }
@@ -28,14 +28,14 @@ class SIMD_SSE2
          m_reg = _mm_set_epi32(B0, B1, B2, B3);
          }
 
-      SIMD_SSE2(u32bit B)
+      explicit SIMD_SSE2(u32bit B)
          {
          m_reg = _mm_set1_epi32(B);
          }
 
       static SIMD_SSE2 load_le(const void* in)
          {
-         return _mm_loadu_si128(reinterpret_cast<const __m128i*>(in));
+         return SIMD_SSE2(_mm_loadu_si128(reinterpret_cast<const __m128i*>(in)));
          }
 
       static SIMD_SSE2 load_be(const void* in)
@@ -71,7 +71,7 @@ class SIMD_SSE2
 
       SIMD_SSE2 operator+(const SIMD_SSE2& other) const
          {
-         return _mm_add_epi32(m_reg, other.m_reg);
+         return SIMD_SSE2(_mm_add_epi32(m_reg, other.m_reg));
          }
 
       void operator-=(const SIMD_SSE2& other)
@@ -81,7 +81,7 @@ class SIMD_SSE2
 
       SIMD_SSE2 operator-(const SIMD_SSE2& other) const
          {
-         return _mm_sub_epi32(m_reg, other.m_reg);
+         return SIMD_SSE2(_mm_sub_epi32(m_reg, other.m_reg));
          }
 
       void operator^=(const SIMD_SSE2& other)
@@ -91,7 +91,7 @@ class SIMD_SSE2
 
       SIMD_SSE2 operator^(const SIMD_SSE2& other) const
          {
-         return _mm_xor_si128(m_reg, other.m_reg);
+         return SIMD_SSE2(_mm_xor_si128(m_reg, other.m_reg));
          }
 
       void operator|=(const SIMD_SSE2& other)
@@ -101,7 +101,7 @@ class SIMD_SSE2
 
       SIMD_SSE2 operator&(const SIMD_SSE2& other)
          {
-         return _mm_and_si128(m_reg, other.m_reg);
+         return SIMD_SSE2(_mm_and_si128(m_reg, other.m_reg));
          }
 
       void operator&=(const SIMD_SSE2& other)
@@ -111,23 +111,23 @@ class SIMD_SSE2
 
       SIMD_SSE2 operator<<(size_t shift) const
          {
-         return _mm_slli_epi32(m_reg, static_cast<int>(shift));
+         return SIMD_SSE2(_mm_slli_epi32(m_reg, static_cast<int>(shift)));
          }
 
       SIMD_SSE2 operator>>(size_t shift) const
          {
-         return _mm_srli_epi32(m_reg, static_cast<int>(shift));
+         return SIMD_SSE2(_mm_srli_epi32(m_reg, static_cast<int>(shift)));
          }
 
       SIMD_SSE2 operator~() const
          {
-         return _mm_xor_si128(m_reg, _mm_set1_epi32(0xFFFFFFFF));
+         return SIMD_SSE2(_mm_xor_si128(m_reg, _mm_set1_epi32(0xFFFFFFFF)));
          }
 
       // (~reg) & other
       SIMD_SSE2 andc(const SIMD_SSE2& other)
          {
-         return _mm_andnot_si128(m_reg, other.m_reg);
+         return SIMD_SSE2(_mm_andnot_si128(m_reg, other.m_reg));
          }
 
       SIMD_SSE2 bswap() const
@@ -137,8 +137,8 @@ class SIMD_SSE2
          T = _mm_shufflehi_epi16(T, _MM_SHUFFLE(2, 3, 0, 1));
          T = _mm_shufflelo_epi16(T, _MM_SHUFFLE(2, 3, 0, 1));
 
-         return _mm_or_si128(_mm_srli_epi16(T, 8),
-                             _mm_slli_epi16(T, 8));
+         return SIMD_SSE2(_mm_or_si128(_mm_srli_epi16(T, 8),
+                             _mm_slli_epi16(T, 8)));
          }
 
       static void transpose(SIMD_SSE2& B0, SIMD_SSE2& B1,
@@ -155,7 +155,7 @@ class SIMD_SSE2
          }
 
    private:
-      SIMD_SSE2(__m128i in) { m_reg = in; }
+      explicit SIMD_SSE2(__m128i in) { m_reg = in; }
 
       __m128i m_reg;
    };