Replace 0 and NULL pointer constants with nullptr. Also fix an old

style cast in secmem.h

67 files changed, 200 insertions, 195 deletions

diff --git a/checks/dolook.cpp b/checks/dolook.cpp
index 20e260f64..364a3f8c3 100644
--- a/checks/dolook.cpp
+++ b/checks/dolook.cpp
@@ -139,7 +139,7 @@ class KDF_Filter : public Filter
 Filter* lookup_pbkdf(const std::string& algname,
                    const std::vector<std::string>& params)
    {
-   PBKDF* pbkdf = 0;
+   PBKDF* pbkdf = nullptr;
 
    try {
       pbkdf = get_pbkdf(algname);
@@ -149,7 +149,7 @@ Filter* lookup_pbkdf(const std::string& algname,
    if(pbkdf)
       return new PBKDF_Filter(pbkdf, params[0], to_u32bit(params[1]),
                               to_u32bit(params[2]));
-   return 0;
+   return nullptr;
    }
 
 void RNG_Filter::write(const byte[], size_t length)
@@ -163,7 +163,7 @@ void RNG_Filter::write(const byte[], size_t length)
 Filter* lookup_rng(const std::string& algname,
                    const std::string& key)
    {
-   RandomNumberGenerator* prng = 0;
+   RandomNumberGenerator* prng = nullptr;
 
 #if defined(BOTAN_HAS_AUTO_SEEDING_RNG)
    if(algname == "AutoSeeded")
@@ -233,21 +233,21 @@ Filter* lookup_rng(const std::string& algname,
       return new RNG_Filter(prng);
       }
 
-   return 0;
+   return nullptr;
    }
 
 Filter* lookup_kdf(const std::string& algname, const std::string& salt,
                    const std::string& params)
    {
-   KDF* kdf = 0;
+   KDF* kdf = nullptr;
    try {
       kdf = get_kdf(algname);
       }
-   catch(...) { return 0; }
+   catch(...) { return nullptr; }
 
    if(kdf)
       return new KDF_Filter(kdf, salt, to_u32bit(params));
-   return 0;
+   return nullptr;
    }
 
 Filter* lookup_encoder(const std::string& algname)
@@ -278,7 +278,7 @@ Filter* lookup_encoder(const std::string& algname)
       return new Zlib_Decompression;
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
@@ -288,7 +288,7 @@ Filter* lookup(const std::string& algname,
    {
    std::string key = params[0];
    std::string iv = params[1];
-   Filter* filter = 0;
+   Filter* filter = nullptr;
 
    // The order of the lookup has to change based on how the names are
    // formatted and parsed.
@@ -304,6 +304,6 @@ Filter* lookup(const std::string& algname,
    filter = lookup_pbkdf(algname, params);
    if(filter) return filter;
 
-   return 0;
+   return nullptr;
    }
 
diff --git a/checks/pk.cpp b/checks/pk.cpp
index 261c5f78c..5ef5df94b 100644
--- a/checks/pk.cpp
+++ b/checks/pk.cpp
@@ -108,7 +108,7 @@ void validate_save_and_load(const Private_Key* priv_key,
       DataSource_Memory input_pub(pub_pem);
       std::auto_ptr<Public_Key> restored_pub(X509::load_key(input_pub));
 
-      if(restored_pub.get() == 0)
+      if(!restored_pub.get())
          std::cout << "Could not recover " << name << " public key\n";
       else if(restored_pub->check_key(rng, true) == false)
          std::cout << "Restored pubkey failed self tests " << name << "\n";
@@ -128,7 +128,7 @@ void validate_save_and_load(const Private_Key* priv_key,
       std::auto_ptr<Private_Key> restored_priv(
          PKCS8::load_key(input_priv, rng));
 
-      if(restored_priv.get() == 0)
+      if(!restored_priv.get())
          std::cout << "Could not recover " << name << " privlic key\n";
       else if(restored_priv->check_key(rng, true) == false)
          std::cout << "Restored privkey failed self tests " << name << "\n";
diff --git a/checks/pk_bench.cpp b/checks/pk_bench.cpp
index 8241ee5d1..da2221b90 100644
--- a/checks/pk_bench.cpp
+++ b/checks/pk_bench.cpp
@@ -83,7 +83,7 @@ const char* ec_domains[] = {
    "secp256r1",
    "secp384r1",
    "secp521r1",
-   0
+   nullptr
 };
 
 class Benchmark_Report
@@ -462,7 +462,7 @@ void benchmark_dsa_nr(RandomNumberGenerator& rng,
    const char* domains[] = { "dsa/jce/1024",
                              "dsa/botan/2048",
                              "dsa/botan/3072",
-                             NULL };
+                             nullptr };
 
    std::string algo_name;
 
@@ -513,7 +513,7 @@ void benchmark_dh(RandomNumberGenerator& rng,
                              "modp/ietf/4096",
                              "modp/ietf/6144",
                              "modp/ietf/8192",
-                             NULL };
+                             nullptr };
 
    for(size_t j = 0; domains[j]; j++)
       {
@@ -574,7 +574,7 @@ void benchmark_dlies(RandomNumberGenerator& rng,
                              "modp/ietf/4096",
                              "modp/ietf/6144",
                              "modp/ietf/8192",
-                             NULL };
+                             nullptr };
 
    for(size_t j = 0; domains[j]; j++)
       {
@@ -633,7 +633,7 @@ void benchmark_elg(RandomNumberGenerator& rng,
                              "modp/ietf/4096",
                              "modp/ietf/6144",
                              "modp/ietf/8192",
-                             NULL };
+                             nullptr };
 
    const std::string algo_name = "ElGamal";
 
diff --git a/checks/validate.cpp b/checks/validate.cpp
index c6a4a29d0..bae5e857f 100644
--- a/checks/validate.cpp
+++ b/checks/validate.cpp
@@ -474,8 +474,10 @@ bool failed_test(const std::string& algo,
 
    try {
       Botan::Filter* test = lookup(algo, params);
-      if(test == 0 && is_extension) return !exp_pass;
-      if(test == 0)
+
+      if(!test && is_extension) return !exp_pass;
+
+      if(!test)
          {
          if(algo != last_missing)
             {
diff --git a/src/algo_factory/algo_cache.h b/src/algo_factory/algo_cache.h
index 3a792c994..11a5580fb 100644
--- a/src/algo_factory/algo_cache.h
+++ b/src/algo_factory/algo_cache.h
@@ -112,7 +112,7 @@ const T* Algorithm_Cache<T>::get(const std::string& algo_spec,
 
    auto algo = find_algorithm(algo_spec);
    if(algo == algorithms.end()) // algo not found at all (no providers)
-      return 0;
+      return nullptr;
 
    // If a provider is requested specifically, return it or fail entirely
    if(requested_provider != "")
@@ -120,10 +120,10 @@ const T* Algorithm_Cache<T>::get(const std::string& algo_spec,
       auto prov = algo->second.find(requested_provider);
       if(prov != algo->second.end())
          return prov->second;
-      return 0;
+      return nullptr;
       }
 
-   const T* prototype = 0;
+   const T* prototype = nullptr;
    std::string prototype_provider;
    size_t prototype_prov_weight = 0;
 
diff --git a/src/algo_factory/algo_factory.cpp b/src/algo_factory/algo_factory.cpp
index 9e4f78569..1683648bd 100644
--- a/src/algo_factory/algo_factory.cpp
+++ b/src/algo_factory/algo_factory.cpp
@@ -30,7 +30,7 @@ template<typename T>
 T* engine_get_algo(Engine*,
                    const SCAN_Name&,
                    Algorithm_Factory&)
-   { return 0; }
+   { return nullptr; }
 
 template<>
 BlockCipher* engine_get_algo(Engine* engine,
@@ -75,7 +75,7 @@ const T* factory_prototype(const std::string& algo_spec,
    SCAN_Name scan_name(algo_spec);
 
    if(scan_name.cipher_mode() != "")
-      return 0;
+      return nullptr;
 
    for(size_t i = 0; i != engines.size(); ++i)
       {
@@ -157,7 +157,7 @@ void Algorithm_Factory::set_preferred_provider(const std::string& algo_spec,
 Engine* Algorithm_Factory::get_engine_n(size_t n) const
    {
    if(n >= engines.size())
-      return 0;
+      return nullptr;
    return engines[n];
    }
 
diff --git a/src/alloc/secmem.h b/src/alloc/secmem.h
index 7c27c8d3b..5ee374b6d 100644
--- a/src/alloc/secmem.h
+++ b/src/alloc/secmem.h
@@ -61,9 +61,10 @@ class secure_allocator
          }
 
       template<typename U, typename... Args>
-        void
-        construct(U* p, Args&&... args)
-        { ::new((void *)p) U(std::forward<Args>(args)...); }
+      void construct(U* p, Args&&... args)
+         {
+         ::new(static_cast<void*>(p)) U(std::forward<Args>(args)...);
+         }
 
       template<typename U> void destroy(U* p) { p->~U(); }
 
diff --git a/src/asn1/ber_dec.cpp b/src/asn1/ber_dec.cpp
index ea0a380d4..dbd59988b 100644
--- a/src/asn1/ber_dec.cpp
+++ b/src/asn1/ber_dec.cpp
@@ -276,7 +276,7 @@ BER_Decoder::BER_Decoder(DataSource& src)
    source = &src;
    owns = false;
    pushed.type_tag = pushed.class_tag = NO_OBJECT;
-   parent = 0;
+   parent = nullptr;
    }
 
 /*
@@ -287,7 +287,7 @@ BER_Decoder::BER_Decoder(const byte data[], size_t length)
    source = new DataSource_Memory(data, length);
    owns = true;
    pushed.type_tag = pushed.class_tag = NO_OBJECT;
-   parent = 0;
+   parent = nullptr;
    }
 
 /*
@@ -298,7 +298,7 @@ BER_Decoder::BER_Decoder(const secure_vector<byte>& data)
    source = new DataSource_Memory(data);
    owns = true;
    pushed.type_tag = pushed.class_tag = NO_OBJECT;
-   parent = 0;
+   parent = nullptr;
    }
 
 /*
@@ -309,7 +309,7 @@ BER_Decoder::BER_Decoder(const std::vector<byte>& data)
    source = new DataSource_Memory(&data[0], data.size());
    owns = true;
    pushed.type_tag = pushed.class_tag = NO_OBJECT;
-   parent = 0;
+   parent = nullptr;
    }
 
 /*
@@ -335,7 +335,7 @@ BER_Decoder::~BER_Decoder()
    {
    if(owns)
       delete source;
-   source = 0;
+   source = nullptr;
    }
 
 /*
diff --git a/src/asn1/der_enc.cpp b/src/asn1/der_enc.cpp
index ea9dfe9f8..594c32539 100644
--- a/src/asn1/der_enc.cpp
+++ b/src/asn1/der_enc.cpp
@@ -205,7 +205,7 @@ DER_Encoder& DER_Encoder::raw_bytes(const byte bytes[], size_t length)
 */
 DER_Encoder& DER_Encoder::encode_null()
    {
-   return add_object(NULL_TAG, UNIVERSAL, 0, 0);
+   return add_object(NULL_TAG, UNIVERSAL, nullptr, 0);
    }
 
 /*
diff --git a/src/block/aes_ssse3/aes_ssse3.cpp b/src/block/aes_ssse3/aes_ssse3.cpp
index 774ccbabb..a9ab29863 100644
--- a/src/block/aes_ssse3/aes_ssse3.cpp
+++ b/src/block/aes_ssse3/aes_ssse3.cpp
@@ -568,7 +568,7 @@ void AES_256_SSSE3::key_schedule(const byte keyb[], size_t)
       _mm_storeu_si128(EK_mm + i, aes_schedule_mangle(key2, i % 4));
       _mm_storeu_si128(DK_mm + (14-i), aes_schedule_mangle_dec(key2, (i+2) % 4));
 
-      key2 = aes_schedule_round(NULL, _mm_shuffle_epi32(key2, 0xFF), k_t);
+      key2 = aes_schedule_round(nullptr, _mm_shuffle_epi32(key2, 0xFF), k_t);
       _mm_storeu_si128(EK_mm + i + 1, aes_schedule_mangle(key2, (i - 1) % 4));
       _mm_storeu_si128(DK_mm + (13-i), aes_schedule_mangle_dec(key2, (i+1) % 4));
       }
diff --git a/src/build-data/cc/gcc.txt b/src/build-data/cc/gcc.txt
index f3babb394..ccbba33fa 100644
--- a/src/build-data/cc/gcc.txt
+++ b/src/build-data/cc/gcc.txt
@@ -11,7 +11,7 @@ add_lib_option -l
 lang_flags "-D_REENTRANT -std=c++0x"
 warning_flags "-W -Wall"
 
-maintainer_warning_flags "-Werror -Wall -Wextra -Wstrict-aliasing -Wstrict-overflow=5 -Wcast-align -Wmissing-declarations -Wpointer-arith -Wcast-qual -Wold-style-cast"
+maintainer_warning_flags "-Werror -Wall -Wextra -Wstrict-aliasing -Wstrict-overflow=5 -Wcast-align -Wmissing-declarations -Wpointer-arith -Wcast-qual -Wold-style-cast -Wzero-as-null-pointer-constant"
 
 lib_opt_flags "-O3"
 check_opt_flags "-O2"
diff --git a/src/cert/x509cert/x509_ext.cpp b/src/cert/x509cert/x509_ext.cpp
index 873de4264..919fb790a 100644
--- a/src/cert/x509cert/x509_ext.cpp
+++ b/src/cert/x509cert/x509_ext.cpp
@@ -36,7 +36,7 @@ Certificate_Extension* Extensions::get_extension(const OID& oid)
    X509_EXTENSION("X509v3.CertificatePolicies", Certificate_Policies);
    X509_EXTENSION("X509v3.ReasonCode", CRL_ReasonCode);
 
-   return 0;
+   return nullptr;
    }
 
 /*
diff --git a/src/cert/x509cert/x509cert.cpp b/src/cert/x509cert/x509cert.cpp
index 8dc4b8b0c..95033f75e 100644
--- a/src/cert/x509cert/x509cert.cpp
+++ b/src/cert/x509cert/x509cert.cpp
@@ -385,7 +385,7 @@ std::string X509_Certificate::to_string() const
                                "DNS",
                                "URI",
                                "PKIX.XMPPAddr",
-                               0 };
+                               nullptr };
 
    std::ostringstream out;
 
diff --git a/src/codec/openpgp/openpgp.cpp b/src/codec/openpgp/openpgp.cpp
index fe6ac6edf..7bd811a2f 100644
--- a/src/codec/openpgp/openpgp.cpp
+++ b/src/codec/openpgp/openpgp.cpp
@@ -136,7 +136,7 @@ secure_vector<byte> PGP_decode(DataSource& source,
       }
 
    Pipe base64(new Base64_Decoder,
-               new Fork(0,
+               new Fork(nullptr,
                         new Chain(new Hash_Filter(new CRC24),
                                   new Base64_Encoder)
                   )
diff --git a/src/constructs/cryptobox/cryptobox.cpp b/src/constructs/cryptobox/cryptobox.cpp
index bb7bf353c..aa2369c6c 100644
--- a/src/constructs/cryptobox/cryptobox.cpp
+++ b/src/constructs/cryptobox/cryptobox.cpp
@@ -64,7 +64,7 @@ std::string encrypt(const byte input[], size_t input_len,
 
    Pipe pipe(get_cipher("Serpent/CTR-BE", cipher_key, iv, ENCRYPTION),
              new Fork(
-                0,
+                nullptr,
                 new MAC_Filter(new HMAC(new SHA_512),
                                mac_key, MAC_OUTPUT_LEN)));
 
diff --git a/src/credentials/credentials_manager.cpp b/src/credentials/credentials_manager.cpp
index 6013fe4ea..adb3a64fc 100644
--- a/src/credentials/credentials_manager.cpp
+++ b/src/credentials/credentials_manager.cpp
@@ -82,7 +82,7 @@ Private_Key* Credentials_Manager::private_key_for(const X509_Certificate&,
                                                   const std::string&,
                                                   const std::string&)
    {
-   return 0;
+   return nullptr;
    }
 
 std::vector<X509_Certificate>
diff --git a/src/engine/asm_engine/asm_engine.cpp b/src/engine/asm_engine/asm_engine.cpp
index 6d475136f..a43a3302d 100644
--- a/src/engine/asm_engine/asm_engine.cpp
+++ b/src/engine/asm_engine/asm_engine.cpp
@@ -40,7 +40,7 @@ Assembler_Engine::find_block_cipher(const SCAN_Name& request,
 #endif
       }
 
-   return 0;
+   return nullptr;
    }
 
 HashFunction*
@@ -66,7 +66,7 @@ Assembler_Engine::find_hash(const SCAN_Name& request,
 #endif
       }
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/core_engine/core_modes.cpp b/src/engine/core_engine/core_modes.cpp
index 8a929e880..ffd8aa04f 100644
--- a/src/engine/core_engine/core_modes.cpp
+++ b/src/engine/core_engine/core_modes.cpp
@@ -111,7 +111,7 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
          else
             return new CTS_Decryption(block_cipher->clone());
 #else
-         return 0;
+         return nullptr;
 #endif
          }
 
@@ -123,7 +123,7 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
          return new CBC_Decryption(block_cipher->clone(),
                                    get_bc_pad(padding, "PKCS7"));
 #else
-      return 0;
+      return nullptr;
 #endif
       }
 
@@ -149,7 +149,7 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
       else if(algo_info.size() == 2)
          bits = to_u32bit(algo_info[1]);
       else
-         return 0;
+         return nullptr;
 
 #if defined(BOTAN_HAS_CFB)
       if(mode_name == "CFB")
@@ -172,7 +172,7 @@ Keyed_Filter* get_cipher_mode(const BlockCipher* block_cipher,
 #endif
       }
 
-   return 0;
+   return nullptr;
    }
 
 /*
@@ -195,10 +195,10 @@ Keyed_Filter* Core_Engine::get_cipher(const std::string& algo_spec,
 
    const BlockCipher* block_cipher = af.prototype_block_cipher(cipher_name);
    if(!block_cipher)
-      return 0;
+      return nullptr;
 
    if(algo_parts.size() >= 4)
-      return 0; // 4 part mode, not something we know about
+      return nullptr; // 4 part mode, not something we know about
 
    if(algo_parts.size() < 2)
       throw Lookup_Error("Cipher specification '" + algo_spec +
@@ -213,7 +213,7 @@ Keyed_Filter* Core_Engine::get_cipher(const std::string& algo_spec,
       padding = (mode == "CBC") ? "PKCS7" : "NoPadding";
 
    if(mode == "ECB" && padding == "CTS")
-      return 0;
+      return nullptr;
    else if((mode != "CBC" && mode != "ECB") && padding != "NoPadding")
       throw Invalid_Algorithm_Name(algo_spec);
 
diff --git a/src/engine/core_engine/def_pk_ops.cpp b/src/engine/core_engine/def_pk_ops.cpp
index db418d5bc..23ba7722c 100644
--- a/src/engine/core_engine/def_pk_ops.cpp
+++ b/src/engine/core_engine/def_pk_ops.cpp
@@ -58,7 +58,7 @@ Core_Engine::get_encryption_op(const Public_Key& key) const
       return new ElGamal_Encryption_Operation(*s);
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Decryption*
@@ -74,7 +74,7 @@ Core_Engine::get_decryption_op(const Private_Key& key) const
       return new ElGamal_Decryption_Operation(*s);
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Key_Agreement*
@@ -90,7 +90,7 @@ Core_Engine::get_key_agreement_op(const Private_Key& key) const
       return new ECDH_KA_Operation(*ecdh);
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Signature*
@@ -127,7 +127,7 @@ Core_Engine::get_signature_op(const Private_Key& key) const
       return new NR_Signature_Operation(*s);
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Verification*
@@ -164,7 +164,7 @@ Core_Engine::get_verify_op(const Public_Key& key) const
       return new NR_Verification_Operation(*s);
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/core_engine/lookup_block.cpp b/src/engine/core_engine/lookup_block.cpp
index c46d4f4cd..a02c75daa 100644
--- a/src/engine/core_engine/lookup_block.cpp
+++ b/src/engine/core_engine/lookup_block.cpp
@@ -277,13 +277,13 @@ BlockCipher* Core_Engine::find_block_cipher(const SCAN_Name& request,
          af.prototype_stream_cipher(request.arg(1));
 
       if(!hash || !stream_cipher)
-         return 0;
+         return nullptr;
 
       return new Lion(hash->clone(), stream_cipher->clone(), block_size);
       }
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/core_engine/lookup_hash.cpp b/src/engine/core_engine/lookup_hash.cpp
index f94a97864..9958d18b9 100644
--- a/src/engine/core_engine/lookup_hash.cpp
+++ b/src/engine/core_engine/lookup_hash.cpp
@@ -218,7 +218,7 @@ HashFunction* Core_Engine::find_hash(const SCAN_Name& request,
          {
          const HashFunction* hash = af.prototype_hash_function(request.arg(i));
          if(!hash)
-            return 0;
+            return nullptr;
 
          hash_prototypes.push_back(hash);
          }
@@ -232,7 +232,7 @@ HashFunction* Core_Engine::find_hash(const SCAN_Name& request,
 
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/core_engine/lookup_mac.cpp b/src/engine/core_engine/lookup_mac.cpp
index 9f322b399..32275b559 100644
--- a/src/engine/core_engine/lookup_mac.cpp
+++ b/src/engine/core_engine/lookup_mac.cpp
@@ -64,7 +64,7 @@ Core_Engine::find_mac(const SCAN_Name& request,
       return new ANSI_X919_MAC(af.make_block_cipher("DES"));
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/core_engine/lookup_pbkdf.cpp b/src/engine/core_engine/lookup_pbkdf.cpp
index 9e9255f0a..2419f4373 100644
--- a/src/engine/core_engine/lookup_pbkdf.cpp
+++ b/src/engine/core_engine/lookup_pbkdf.cpp
@@ -46,7 +46,7 @@ PBKDF* Core_Engine::find_pbkdf(const SCAN_Name& algo_spec,
       return new OpenPGP_S2K(af.make_hash_function(algo_spec.arg(0)));
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/core_engine/lookup_stream.cpp b/src/engine/core_engine/lookup_stream.cpp
index 5b4859c1a..50e246756 100644
--- a/src/engine/core_engine/lookup_stream.cpp
+++ b/src/engine/core_engine/lookup_stream.cpp
@@ -55,7 +55,7 @@ Core_Engine::find_stream_cipher(const SCAN_Name& request,
       return new WiderWake_41_BE;
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/dyn_engine/dyn_engine.cpp b/src/engine/dyn_engine/dyn_engine.cpp
index 2d8dbae3b..078ec4b83 100644
--- a/src/engine/dyn_engine/dyn_engine.cpp
+++ b/src/engine/dyn_engine/dyn_engine.cpp
@@ -21,7 +21,7 @@ extern "C" {
 
 Dynamically_Loaded_Engine::Dynamically_Loaded_Engine(
    const std::string& library_path) :
-   engine(0)
+   engine(nullptr)
    {
    lib = new Dynamically_Loaded_Library(library_path);
 
@@ -49,7 +49,7 @@ Dynamically_Loaded_Engine::Dynamically_Loaded_Engine(
    catch(...)
       {
       delete lib;
-      lib = 0;
+      lib = nullptr;
       throw;
       }
    }
diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index 80712a2f8..d4f6885bc 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -13,79 +13,79 @@ BlockCipher*
 Engine::find_block_cipher(const SCAN_Name&,
                           Algorithm_Factory&) const
    {
-   return 0;
+   return nullptr;
    }
 
 StreamCipher*
 Engine::find_stream_cipher(const SCAN_Name&,
                            Algorithm_Factory&) const
    {
-   return 0;
+   return nullptr;
    }
 
 HashFunction*
 Engine::find_hash(const SCAN_Name&,
                   Algorithm_Factory&) const
    {
-   return 0;
+   return nullptr;
    }
 
 MessageAuthenticationCode*
 Engine::find_mac(const SCAN_Name&,
                  Algorithm_Factory&) const
    {
-   return 0;
+   return nullptr;
    }
 
 PBKDF*
 Engine::find_pbkdf(const SCAN_Name&,
                    Algorithm_Factory&) const
    {
-   return 0;
+   return nullptr;
    }
 
 Modular_Exponentiator*
 Engine::mod_exp(const BigInt&,
                 Power_Mod::Usage_Hints) const
    {
-   return 0;
+   return nullptr;
    }
 
 Keyed_Filter* Engine::get_cipher(const std::string&,
                                  Cipher_Dir,
                                  Algorithm_Factory&)
    {
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Key_Agreement*
 Engine::get_key_agreement_op(const Private_Key&) const
    {
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Signature*
 Engine::get_signature_op(const Private_Key&) const
    {
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Verification*
 Engine::get_verify_op(const Public_Key&) const
    {
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Encryption*
 Engine::get_encryption_op(const Public_Key&) const
    {
-   return 0;
+   return nullptr;
    }
 
 PK_Ops::Decryption*
 Engine::get_decryption_op(const Private_Key&) const
    {
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/engine/simd_engine/simd_engine.cpp b/src/engine/simd_engine/simd_engine.cpp
index f9a731a82..70529f1fd 100644
--- a/src/engine/simd_engine/simd_engine.cpp
+++ b/src/engine/simd_engine/simd_engine.cpp
@@ -68,7 +68,7 @@ SIMD_Engine::find_block_cipher(const SCAN_Name& request,
       return new XTEA_SIMD;
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 HashFunction*
@@ -80,7 +80,7 @@ SIMD_Engine::find_hash(const SCAN_Name& request,
       return new SHA_160_SSE2;
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/entropy/dev_random/dev_random.cpp b/src/entropy/dev_random/dev_random.cpp
index d92176ce9..3090f9510 100644
--- a/src/entropy/dev_random/dev_random.cpp
+++ b/src/entropy/dev_random/dev_random.cpp
@@ -45,7 +45,7 @@ size_t Device_EntropySource::Device_Reader::get(byte out[], size_t length,
    timeout.tv_sec = (ms_wait_time / 1000);
    timeout.tv_usec = (ms_wait_time % 1000) * 1000;
 
-   if(::select(fd + 1, &read_set, 0, 0, &timeout) < 0)
+   if(::select(fd + 1, &read_set, nullptr, nullptr, &timeout) < 0)
       return 0;
 
    if(!(FD_ISSET(fd, &read_set)))
diff --git a/src/entropy/proc_walk/es_ftw.cpp b/src/entropy/proc_walk/es_ftw.cpp
index d65aadfb1..7d72e7752 100644
--- a/src/entropy/proc_walk/es_ftw.cpp
+++ b/src/entropy/proc_walk/es_ftw.cpp
@@ -42,7 +42,7 @@ class Directory_Walker : public File_Descriptor_Source
    {
    public:
       Directory_Walker(const std::string& root) :
-         m_cur_dir(std::make_pair<DIR*, std::string>(0, ""))
+         m_cur_dir(std::make_pair<DIR*, std::string>(nullptr, ""))
          {
          if(DIR* root_dir = ::opendir(root.c_str()))
             m_cur_dir = std::make_pair(root_dir, root);
@@ -75,9 +75,9 @@ std::pair<struct dirent*, std::string> Directory_Walker::get_next_dirent()
          return std::make_pair(dir, m_cur_dir.second);
 
       ::closedir(m_cur_dir.first);
-      m_cur_dir = std::make_pair<DIR*, std::string>(0, "");
+      m_cur_dir = std::make_pair<DIR*, std::string>(nullptr, "");
 
-      while(!m_dirlist.empty() && m_cur_dir.first == 0)
+      while(!m_dirlist.empty() && !m_cur_dir.first)
          {
          const std::string next_dir_name = m_dirlist[0];
          m_dirlist.pop_front();
@@ -87,7 +87,7 @@ std::pair<struct dirent*, std::string> Directory_Walker::get_next_dirent()
          }
       }
 
-   return std::make_pair<struct dirent*, std::string>(0, ""); // nothing left
+   return std::make_pair<struct dirent*, std::string>(nullptr, ""); // nothing left
    }
 
 int Directory_Walker::next_fd()
@@ -131,9 +131,8 @@ int Directory_Walker::next_fd()
 /**
 * FTW_EntropySource Constructor
 */
-FTW_EntropySource::FTW_EntropySource(const std::string& p) : path(p)
+FTW_EntropySource::FTW_EntropySource(const std::string& p) : path(p), dir(nullptr)
    {
-   dir = 0;
    }
 
 /**
@@ -142,6 +141,7 @@ FTW_EntropySource::FTW_EntropySource(const std::string& p) : path(p)
 FTW_EntropySource::~FTW_EntropySource()
    {
    delete dir;
+   dir = nullptr;
    }
 
 void FTW_EntropySource::poll(Entropy_Accumulator& accum)
@@ -161,7 +161,7 @@ void FTW_EntropySource::poll(Entropy_Accumulator& accum)
       if(fd == -1)
          {
          delete dir;
-         dir = 0;
+         dir = nullptr;
          break;
          }
 
diff --git a/src/entropy/unix_procs/es_unix.cpp b/src/entropy/unix_procs/es_unix.cpp
index 9ec5f7148..f72a691d2 100644
--- a/src/entropy/unix_procs/es_unix.cpp
+++ b/src/entropy/unix_procs/es_unix.cpp
@@ -68,7 +68,7 @@ void Unix_EntropySource::poll(Entropy_Accumulator& accum)
       "/etc/passwd",
       ".",
       "..",
-      0 };
+      nullptr };
 
    for(size_t i = 0; stat_targets[i]; i++)
       {
diff --git a/src/entropy/unix_procs/unix_cmd.cpp b/src/entropy/unix_procs/unix_cmd.cpp
index 930444075..823da2717 100644
--- a/src/entropy/unix_procs/unix_cmd.cpp
+++ b/src/entropy/unix_procs/unix_cmd.cpp
@@ -29,10 +29,10 @@ void do_exec(const std::vector<std::string>& arg_list,
    {
    const size_t args = arg_list.size() - 1;
 
-   const char* arg1 = (args >= 1) ? arg_list[1].c_str() : 0;
-   const char* arg2 = (args >= 2) ? arg_list[2].c_str() : 0;
-   const char* arg3 = (args >= 3) ? arg_list[3].c_str() : 0;
-   const char* arg4 = (args >= 4) ? arg_list[4].c_str() : 0;
+   const char* arg1 = (args >= 1) ? arg_list[1].c_str() : nullptr;
+   const char* arg2 = (args >= 2) ? arg_list[2].c_str() : nullptr;
+   const char* arg3 = (args >= 3) ? arg_list[3].c_str() : nullptr;
+   const char* arg4 = (args >= 4) ? arg_list[4].c_str() : nullptr;
 
    for(size_t j = 0; j != paths.size(); j++)
       {
@@ -74,7 +74,7 @@ size_t DataSource_Command::read(byte buf[], size_t length)
    tv.tv_usec = MAX_BLOCK_USECS;
 
    ssize_t got = 0;
-   if(::select(pipe->fd + 1, &set, 0, 0, &tv) == 1)
+   if(::select(pipe->fd + 1, &set, nullptr, nullptr, &tv) == 1)
       {
       if(FD_ISSET(pipe->fd, &set))
          got = ::read(pipe->fd, buf, length);
@@ -182,7 +182,7 @@ void DataSource_Command::shutdown_pipe()
    {
    if(pipe)
       {
-      pid_t reaped = waitpid(pipe->pid, 0, WNOHANG);
+      pid_t reaped = waitpid(pipe->pid, nullptr, WNOHANG);
 
       if(reaped == 0)
          {
@@ -191,21 +191,21 @@ void DataSource_Command::shutdown_pipe()
          struct ::timeval tv;
          tv.tv_sec = 0;
          tv.tv_usec = KILL_WAIT;
-         select(0, 0, 0, 0, &tv);
+         select(0, nullptr, nullptr, nullptr, &tv);
 
-         reaped = ::waitpid(pipe->pid, 0, WNOHANG);
+         reaped = ::waitpid(pipe->pid, nullptr, WNOHANG);
 
          if(reaped == 0)
             {
             ::kill(pipe->pid, SIGKILL);
             do
-               reaped = ::waitpid(pipe->pid, 0, 0);
+               reaped = ::waitpid(pipe->pid, nullptr, 0);
             while(reaped == -1);
             }
          }
 
       delete pipe;
-      pipe = 0;
+      pipe = nullptr;
       }
    }
 
@@ -223,7 +223,7 @@ DataSource_Command::DataSource_Command(const std::string& prog_and_args,
    if(arg_list.size() > 5)
       throw Invalid_Argument("DataSource_Command: Too many args");
 
-   pipe = 0;
+   pipe = nullptr;
    create_pipe(paths);
    }
 
diff --git a/src/filters/basefilt.h b/src/filters/basefilt.h
index adde3dd54..5252be973 100644
--- a/src/filters/basefilt.h
+++ b/src/filters/basefilt.h
@@ -39,7 +39,8 @@ class BOTAN_DLL Chain : public Fanout_Filter
       * Construct a chain of up to four filters. The filters are set
       * up in the same order as the arguments.
       */
-      Chain(Filter* = 0, Filter* = 0, Filter* = 0, Filter* = 0);
+      Chain(Filter* = nullptr, Filter* = nullptr,
+            Filter* = nullptr, Filter* = nullptr);
 
       /**
       * Construct a chain from range of filters
@@ -65,7 +66,7 @@ class BOTAN_DLL Fork : public Fanout_Filter
       /**
       * Construct a Fork filter with up to four forks.
       */
-      Fork(Filter*, Filter*, Filter* = 0, Filter* = 0);
+      Fork(Filter*, Filter*, Filter* = nullptr, Filter* = nullptr);
 
       /**
       * Construct a Fork from range of filters
diff --git a/src/filters/data_snk.cpp b/src/filters/data_snk.cpp
index d651dcba7..2903e5e1f 100644
--- a/src/filters/data_snk.cpp
+++ b/src/filters/data_snk.cpp
@@ -29,7 +29,7 @@ void DataSink_Stream::write(const byte out[], size_t length)
 DataSink_Stream::DataSink_Stream(std::ostream& out,
                                  const std::string& name) :
    identifier(name),
-   sink_p(0),
+   sink_p(nullptr),
    sink(out)
    {
    }
diff --git a/src/filters/data_src.cpp b/src/filters/data_src.cpp
index 4980507ca..cc100ab13 100644
--- a/src/filters/data_src.cpp
+++ b/src/filters/data_src.cpp
@@ -174,7 +174,7 @@ DataSource_Stream::DataSource_Stream(const std::string& path,
 DataSource_Stream::DataSource_Stream(std::istream& in,
                                      const std::string& name) :
    identifier(name),
-   source_p(0),
+   source_p(nullptr),
    source(in),
    total_read(0)
    {
diff --git a/src/filters/filter.cpp b/src/filters/filter.cpp
index c33f25814..9432f0304 100644
--- a/src/filters/filter.cpp
+++ b/src/filters/filter.cpp
@@ -96,7 +96,7 @@ Filter* Filter::get_next() const
    {
    if(port_num < next.size())
       return next[port_num];
-   return 0;
+   return nullptr;
    }
 
 /*
@@ -104,7 +104,7 @@ Filter* Filter::get_next() const
 */
 void Filter::set_next(Filter* filters[], size_t size)
    {
-   while(size && filters && filters[size-1] == 0)
+   while(size && filters && filters[size-1] == nullptr)
       --size;
 
    next.clear();
diff --git a/src/filters/modes/eax/eax.cpp b/src/filters/modes/eax/eax.cpp
index fb75d73fd..e67f03f68 100644
--- a/src/filters/modes/eax/eax.cpp
+++ b/src/filters/modes/eax/eax.cpp
@@ -70,7 +70,7 @@ void EAX_Base::set_key(const SymmetricKey& key)
    ctr->set_key(key);
    cmac->set_key(key);
 
-   header_mac = eax_prf(1, BLOCK_SIZE, cmac, 0, 0);
+   header_mac = eax_prf(1, BLOCK_SIZE, cmac, nullptr, 0);
    }
 
 /*
diff --git a/src/filters/out_buf.cpp b/src/filters/out_buf.cpp
index 7b79b4b70..b1dc8ff7f 100644
--- a/src/filters/out_buf.cpp
+++ b/src/filters/out_buf.cpp
@@ -69,7 +69,7 @@ void Output_Buffers::retire()
       if(buffers[i] && buffers[i]->size() == 0)
          {
          delete buffers[i];
-         buffers[i] = 0;
+         buffers[i] = nullptr;
          }
 
    while(buffers.size() && !buffers[0])
@@ -85,7 +85,7 @@ void Output_Buffers::retire()
 SecureQueue* Output_Buffers::get(Pipe::message_id msg) const
    {
    if(msg < offset)
-      return 0;
+      return nullptr;
 
    BOTAN_ASSERT(msg < message_count(),
                 "Message number out of range");
diff --git a/src/filters/pipe.cpp b/src/filters/pipe.cpp
index 6664098b3..e3c2f53b6 100644
--- a/src/filters/pipe.cpp
+++ b/src/filters/pipe.cpp
@@ -66,7 +66,7 @@ Pipe::~Pipe()
 void Pipe::init()
    {
    outputs = new Output_Buffers;
-   pipe = 0;
+   pipe = nullptr;
    default_read = 0;
    inside_msg = false;
    }
@@ -77,7 +77,7 @@ void Pipe::init()
 void Pipe::reset()
    {
    destruct(pipe);
-   pipe = 0;
+   pipe = nullptr;
    inside_msg = false;
    }
 
@@ -159,7 +159,7 @@ void Pipe::start_msg()
    {
    if(inside_msg)
       throw Invalid_State("Pipe::start_msg: Message was already started");
-   if(pipe == 0)
+   if(pipe == nullptr)
       pipe = new Null_Filter;
    find_endpoints(pipe);
    pipe->new_msg();
@@ -178,7 +178,7 @@ void Pipe::end_msg()
    if(dynamic_cast<Null_Filter*>(pipe))
       {
       delete pipe;
-      pipe = 0;
+      pipe = nullptr;
       }
    inside_msg = false;
 
@@ -210,7 +210,7 @@ void Pipe::clear_endpoints(Filter* f)
    for(size_t j = 0; j != f->total_ports(); ++j)
       {
       if(f->next[j] && dynamic_cast<SecureQueue*>(f->next[j]))
-         f->next[j] = 0;
+         f->next[j] = nullptr;
       clear_endpoints(f->next[j]);
       }
    }
diff --git a/src/filters/pipe.h b/src/filters/pipe.h
index e53f0d508..3236e7c36 100644
--- a/src/filters/pipe.h
+++ b/src/filters/pipe.h
@@ -276,7 +276,8 @@ class BOTAN_DLL Pipe : public DataSource
       * Construct a Pipe of up to four filters. The filters are set up
       * in the same order as the arguments.
       */
-      Pipe(Filter* = 0, Filter* = 0, Filter* = 0, Filter* = 0);
+      Pipe(Filter* = nullptr, Filter* = nullptr,
+           Filter* = nullptr, Filter* = nullptr);
 
       /**
       * Construct a Pipe from a list of filters
diff --git a/src/filters/secqueue.cpp b/src/filters/secqueue.cpp
index 63d4f88d3..811a7ef57 100644
--- a/src/filters/secqueue.cpp
+++ b/src/filters/secqueue.cpp
@@ -17,9 +17,9 @@ class SecureQueueNode
    {
    public:
       SecureQueueNode() : buffer(DEFAULT_BUFFERSIZE)
-         { next = 0; start = end = 0; }
+         { next = nullptr; start = end = 0; }
 
-      ~SecureQueueNode() { next = 0; start = end = 0; }
+      ~SecureQueueNode() { next = nullptr; start = end = 0; }
 
       size_t write(const byte input[], size_t length)
          {
@@ -59,7 +59,7 @@ class SecureQueueNode
 */
 SecureQueue::SecureQueue()
    {
-   set_next(0, 0);
+   set_next(nullptr, 0);
    head = tail = new SecureQueueNode;
    }
 
@@ -69,7 +69,7 @@ SecureQueue::SecureQueue()
 SecureQueue::SecureQueue(const SecureQueue& input) :
    Fanout_Filter(), DataSource()
    {
-   set_next(0, 0);
+   set_next(nullptr, 0);
 
    head = tail = new SecureQueueNode;
    SecureQueueNode* temp = input.head;
@@ -92,7 +92,7 @@ void SecureQueue::destroy()
       delete temp;
       temp = holder;
       }
-   head = tail = 0;
+   head = tail = nullptr;
    }
 
 /*
diff --git a/src/libstate/get_enc.cpp b/src/libstate/get_enc.cpp
index b7c9a7146..00297464b 100644
--- a/src/libstate/get_enc.cpp
+++ b/src/libstate/get_enc.cpp
@@ -151,7 +151,7 @@ EME* get_eme(const std::string& algo_spec)
    Algorithm_Factory& af = global_state().algorithm_factory();
 
    if(request.algo_name() == "Raw")
-      return 0; // No padding
+      return nullptr; // No padding
 
 #if defined(BOTAN_HAS_EME_PKCS1v15)
    if(request.algo_name() == "PKCS1v15" && request.arg_count() == 0)
@@ -182,7 +182,7 @@ KDF* get_kdf(const std::string& algo_spec)
    Algorithm_Factory& af = global_state().algorithm_factory();
 
    if(request.algo_name() == "Raw")
-      return 0; // No KDF
+      return nullptr; // No KDF
 
 #if defined(BOTAN_HAS_KDF1)
    if(request.algo_name() == "KDF1" && request.arg_count() == 1)
diff --git a/src/libstate/global_rng.cpp b/src/libstate/global_rng.cpp
index f80146596..65da38f5f 100644
--- a/src/libstate/global_rng.cpp
+++ b/src/libstate/global_rng.cpp
@@ -169,7 +169,7 @@ class Serialized_PRNG : public RandomNumberGenerator
 RandomNumberGenerator* Library_State::make_global_rng(Algorithm_Factory& af,
                                                       std::mutex& mutex)
    {
-   RandomNumberGenerator* rng = 0;
+   RandomNumberGenerator* rng = nullptr;
 
 #if defined(BOTAN_HAS_HMAC_RNG)
 
diff --git a/src/libstate/global_state.cpp b/src/libstate/global_state.cpp
index 34bcd03fc..6a846d9b0 100644
--- a/src/libstate/global_state.cpp
+++ b/src/libstate/global_state.cpp
@@ -22,7 +22,7 @@ namespace Global_State_Management {
 */
 namespace {
 
-Library_State* global_lib_state = 0;
+Library_State* global_lib_state = nullptr;
 
 }
 
@@ -83,7 +83,7 @@ Library_State* swap_global_state(Library_State* new_state)
 */
 bool global_state_exists()
    {
-   return (global_lib_state != 0);
+   return (global_lib_state != nullptr);
    }
 
 }
diff --git a/src/libstate/init.cpp b/src/libstate/init.cpp
index 6ab303909..2d724f366 100644
--- a/src/libstate/init.cpp
+++ b/src/libstate/init.cpp
@@ -41,7 +41,7 @@ void LibraryInitializer::initialize(const std::string&)
 */
 void LibraryInitializer::deinitialize()
    {
-   Global_State_Management::set_global_state(0);
+   Global_State_Management::set_global_state(nullptr);
    }
 
 }
diff --git a/src/libstate/libstate.cpp b/src/libstate/libstate.cpp
index eafa6dbb0..7ddfddfca 100644
--- a/src/libstate/libstate.cpp
+++ b/src/libstate/libstate.cpp
@@ -168,9 +168,9 @@ void Library_State::initialize()
 */
 Library_State::Library_State()
    {
-   m_algorithm_factory = 0;
+   m_algorithm_factory = nullptr;
 
-   global_rng_ptr = 0;
+   global_rng_ptr = nullptr;
    }
 
 /*
@@ -179,10 +179,10 @@ Library_State::Library_State()
 Library_State::~Library_State()
    {
    delete m_algorithm_factory;
-   m_algorithm_factory = 0;
+   m_algorithm_factory = nullptr;
 
    delete global_rng_ptr;
-   global_rng_ptr = 0;
+   global_rng_ptr = nullptr;
    }
 
 }
diff --git a/src/libstate/lookup.h b/src/libstate/lookup.h
index e10c195b8..96364e1d9 100644
--- a/src/libstate/lookup.h
+++ b/src/libstate/lookup.h
@@ -235,7 +235,7 @@ BOTAN_DLL bool have_algorithm(const std::string& algo_spec);
 inline bool have_block_cipher(const std::string& algo_spec)
    {
    Algorithm_Factory& af = global_state().algorithm_factory();
-   return (af.prototype_block_cipher(algo_spec) != 0);
+   return (af.prototype_block_cipher(algo_spec) != nullptr);
    }
 
 /**
@@ -248,7 +248,7 @@ inline bool have_block_cipher(const std::string& algo_spec)
 inline bool have_stream_cipher(const std::string& algo_spec)
    {
    Algorithm_Factory& af = global_state().algorithm_factory();
-   return (af.prototype_stream_cipher(algo_spec) != 0);
+   return (af.prototype_stream_cipher(algo_spec) != nullptr);
    }
 
 /**
@@ -261,7 +261,7 @@ inline bool have_stream_cipher(const std::string& algo_spec)
 inline bool have_hash(const std::string& algo_spec)
    {
    Algorithm_Factory& af = global_state().algorithm_factory();
-   return (af.prototype_hash_function(algo_spec) != 0);
+   return (af.prototype_hash_function(algo_spec) != nullptr);
    }
 
 /**
@@ -274,7 +274,7 @@ inline bool have_hash(const std::string& algo_spec)
 inline bool have_mac(const std::string& algo_spec)
    {
    Algorithm_Factory& af = global_state().algorithm_factory();
-   return (af.prototype_mac(algo_spec) != 0);
+   return (af.prototype_mac(algo_spec) != nullptr);
    }
 
 /*
diff --git a/src/math/numbertheory/pow_mod.cpp b/src/math/numbertheory/pow_mod.cpp
index bf6b29275..c7d7fe70e 100644
--- a/src/math/numbertheory/pow_mod.cpp
+++ b/src/math/numbertheory/pow_mod.cpp
@@ -16,7 +16,7 @@ namespace Botan {
 */
 Power_Mod::Power_Mod(const BigInt& n, Usage_Hints hints)
    {
-   core = 0;
+   core = nullptr;
    set_modulus(n, hints);
    }
 
@@ -25,7 +25,7 @@ Power_Mod::Power_Mod(const BigInt& n, Usage_Hints hints)
 */
 Power_Mod::Power_Mod(const Power_Mod& other)
    {
-   core = 0;
+   core = nullptr;
    if(other.core)
       core = other.core->copy();
    }
@@ -36,7 +36,7 @@ Power_Mod::Power_Mod(const Power_Mod& other)
 Power_Mod& Power_Mod::operator=(const Power_Mod& other)
    {
    delete core;
-   core = 0;
+   core = nullptr;
    if(other.core)
       core = other.core->copy();
    return (*this);
@@ -56,7 +56,7 @@ Power_Mod::~Power_Mod()
 void Power_Mod::set_modulus(const BigInt& n, Usage_Hints hints) const
    {
    delete core;
-   core = 0;
+   core = nullptr;
 
    if(n != 0)
       {
diff --git a/src/passhash/passhash9/passhash9.cpp b/src/passhash/passhash9/passhash9.cpp
index cbfe668f1..af7ed761b 100644
--- a/src/passhash/passhash9/passhash9.cpp
+++ b/src/passhash/passhash9/passhash9.cpp
@@ -40,7 +40,7 @@ MessageAuthenticationCode* get_pbkdf_prf(byte alg_id)
       }
    catch(Algorithm_Not_Found) {}
 
-   return 0;
+   return nullptr;
    }
 
 }
@@ -120,7 +120,7 @@ bool check_passhash9(const std::string& pass, const std::string& hash)
 
    MessageAuthenticationCode* pbkdf_prf = get_pbkdf_prf(alg_id);
 
-   if(pbkdf_prf == 0)
+   if(!pbkdf_prf)
       return false; // unknown algorithm, reject
 
    PKCS5_PBKDF2 kdf(pbkdf_prf); // takes ownership of pointer
diff --git a/src/pbe/pbes2/pbes2.cpp b/src/pbe/pbes2/pbes2.cpp
index 384fc3d90..752a4fb6d 100644
--- a/src/pbe/pbes2/pbes2.cpp
+++ b/src/pbe/pbes2/pbes2.cpp
@@ -228,8 +228,8 @@ PBE_PKCS5v20::PBE_PKCS5v20(BlockCipher* cipher,
 */
 PBE_PKCS5v20::PBE_PKCS5v20(DataSource& params) : direction(DECRYPTION)
    {
-   hash_function = 0;
-   block_cipher = 0;
+   hash_function = nullptr;
+   block_cipher = nullptr;
    decode_params(params);
    }
 
diff --git a/src/pk_pad/emsa3/emsa3.cpp b/src/pk_pad/emsa3/emsa3.cpp
index 493140a63..0d603c508 100644
--- a/src/pk_pad/emsa3/emsa3.cpp
+++ b/src/pk_pad/emsa3/emsa3.cpp
@@ -129,7 +129,7 @@ secure_vector<byte> EMSA3_Raw::encoding_of(const secure_vector<byte>& msg,
                                           size_t output_bits,
                                           RandomNumberGenerator&)
    {
-   return emsa3_encoding(msg, output_bits, 0, 0);
+   return emsa3_encoding(msg, output_bits, nullptr, 0);
    }
 
 /*
@@ -141,7 +141,7 @@ bool EMSA3_Raw::verify(const secure_vector<byte>& coded,
    {
    try
       {
-      return (coded == emsa3_encoding(raw, key_bits, 0, 0));
+      return (coded == emsa3_encoding(raw, key_bits, nullptr, 0));
       }
    catch(...)
       {
diff --git a/src/pubkey/pk_algs.cpp b/src/pubkey/pk_algs.cpp
index 863eb57e4..9673199e0 100644
--- a/src/pubkey/pk_algs.cpp
+++ b/src/pubkey/pk_algs.cpp
@@ -98,7 +98,7 @@ Public_Key* make_public_key(const AlgorithmIdentifier& alg_id,
       return new ECDH_PublicKey(alg_id, key_bits);
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 Private_Key* make_private_key(const AlgorithmIdentifier& alg_id,
@@ -154,7 +154,7 @@ Private_Key* make_private_key(const AlgorithmIdentifier& alg_id,
       return new ECDH_PrivateKey(alg_id, key_bits);
 #endif
 
-   return 0;
+   return nullptr;
    }
 
 }
diff --git a/src/pubkey/pubkey.cpp b/src/pubkey/pubkey.cpp
index 370eeddbf..c27cf4a05 100644
--- a/src/pubkey/pubkey.cpp
+++ b/src/pubkey/pubkey.cpp
@@ -38,7 +38,7 @@ PK_Encryptor_EME::PK_Encryptor_EME(const Public_Key& key,
       throw Lookup_Error("PK_Encryptor_EME: No working engine for " +
                          key.algo_name());
 
-   eme = (eme_name == "Raw") ? 0 : get_eme(eme_name);
+   eme = (eme_name == "Raw") ? nullptr : get_eme(eme_name);
    }
 
 /*
@@ -98,7 +98,7 @@ PK_Decryptor_EME::PK_Decryptor_EME(const Private_Key& key,
       throw Lookup_Error("PK_Decryptor_EME: No working engine for " +
                          key.algo_name());
 
-   eme = (eme_name == "Raw") ? 0 : get_eme(eme_name);
+   eme = (eme_name == "Raw") ? nullptr : get_eme(eme_name);
    }
 
 /*
@@ -130,8 +130,8 @@ PK_Signer::PK_Signer(const Private_Key& key,
    {
    Algorithm_Factory::Engine_Iterator i(global_state().algorithm_factory());
 
-   op = 0;
-   verify_op = 0;
+   op = nullptr;
+   verify_op = nullptr;
 
    while(const Engine* engine = i.next())
       {
@@ -370,7 +370,7 @@ PK_Key_Agreement::PK_Key_Agreement(const PK_Key_Agreement_Key& key,
       throw Lookup_Error("PK_Key_Agreement: No working engine for " +
                          key.algo_name());
 
-   kdf = (kdf_name == "Raw") ? 0 : get_kdf(kdf_name);
+   kdf = (kdf_name == "Raw") ? nullptr : get_kdf(kdf_name);
    }
 
 SymmetricKey PK_Key_Agreement::derive_key(size_t key_len, const byte in[],
diff --git a/src/stream/ctr/ctr.cpp b/src/stream/ctr/ctr.cpp
index 8ceac858a..87ec86c65 100644
--- a/src/stream/ctr/ctr.cpp
+++ b/src/stream/ctr/ctr.cpp
@@ -49,7 +49,7 @@ void CTR_BE::key_schedule(const byte key[], size_t key_len)
    permutation->set_key(key, key_len);
 
    // Set a default all-zeros IV
-   set_iv(0, 0);
+   set_iv(nullptr, 0);
    }
 
 /*
diff --git a/src/stream/ofb/ofb.cpp b/src/stream/ofb/ofb.cpp
index 02521581b..1137a58af 100644
--- a/src/stream/ofb/ofb.cpp
+++ b/src/stream/ofb/ofb.cpp
@@ -46,7 +46,7 @@ void OFB::key_schedule(const byte key[], size_t key_len)
    permutation->set_key(key, key_len);
 
    // Set a default all-zeros IV
-   set_iv(0, 0);
+   set_iv(nullptr, 0);
    }
 
 /*
diff --git a/src/stream/turing/turing.cpp b/src/stream/turing/turing.cpp
index c455185b0..10ac18315 100644
--- a/src/stream/turing/turing.cpp
+++ b/src/stream/turing/turing.cpp
@@ -273,7 +273,7 @@ void Turing::key_schedule(const byte key[], size_t length)
       S3[i] = (W3 & 0xFFFFFF00) | C3;
       }
 
-   set_iv(0, 0);
+   set_iv(nullptr, 0);
    }
 
 /*
diff --git a/src/tls/rec_read.cpp b/src/tls/rec_read.cpp
index 4a1d6aac1..fd57496c8 100644
--- a/src/tls/rec_read.cpp
+++ b/src/tls/rec_read.cpp
@@ -18,7 +18,7 @@ namespace TLS {
 
 Record_Reader::Record_Reader() :
    m_readbuf(TLS_HEADER_SIZE + MAX_CIPHERTEXT_SIZE),
-   m_mac(0)
+   m_mac(nullptr)
    {
    reset();
    set_maximum_fragment_size(0);
@@ -37,7 +37,7 @@ void Record_Reader::reset()
    m_cipher.reset();
 
    delete m_mac;
-   m_mac = 0;
+   m_mac = nullptr;
 
    m_block_size = 0;
    m_iv_size = 0;
@@ -72,7 +72,7 @@ void Record_Reader::activate(Connection_Side side,
    {
    m_cipher.reset();
    delete m_mac;
-   m_mac = 0;
+   m_mac = nullptr;
    m_seq_no = 0;
 
    if(compression_method != NO_COMPRESSION)
diff --git a/src/tls/rec_wri.cpp b/src/tls/rec_wri.cpp
index 63383f85e..d18ab6594 100644
--- a/src/tls/rec_wri.cpp
+++ b/src/tls/rec_wri.cpp
@@ -25,7 +25,7 @@ namespace TLS {
 Record_Writer::Record_Writer(std::function<void (const byte[], size_t)> out) :
    m_output_fn(out),
    m_writebuf(TLS_HEADER_SIZE + MAX_CIPHERTEXT_SIZE),
-   m_mac(0)
+   m_mac(nullptr)
    {
    reset();
    set_maximum_fragment_size(0);
@@ -48,7 +48,7 @@ void Record_Writer::reset()
    m_cipher.reset();
 
    delete m_mac;
-   m_mac = 0;
+   m_mac = nullptr;
 
    m_version = Protocol_Version();
    m_block_size = 0;
@@ -76,7 +76,7 @@ void Record_Writer::activate(Connection_Side side,
    {
    m_cipher.reset();
    delete m_mac;
-   m_mac = 0;
+   m_mac = nullptr;
 
    if(compression_method != NO_COMPRESSION)
       throw Internal_Error("Negotiated unknown compression algorithm");
diff --git a/src/tls/s_kex.cpp b/src/tls/s_kex.cpp
index d28b44857..48901d311 100644
--- a/src/tls/s_kex.cpp
+++ b/src/tls/s_kex.cpp
@@ -33,7 +33,7 @@ Server_Key_Exchange::Server_Key_Exchange(Record_Writer& writer,
                                          Credentials_Manager& creds,
                                          RandomNumberGenerator& rng,
                                          const Private_Key* signing_key) :
-   m_kex_key(0), m_srp_params(0)
+   m_kex_key(nullptr), m_srp_params(nullptr)
    {
    const std::string hostname = state->client_hello->sni_hostname();
    const std::string kex_algo = state->suite.kex_algo();
@@ -146,7 +146,7 @@ Server_Key_Exchange::Server_Key_Exchange(const std::vector<byte>& buf,
                                          const std::string& kex_algo,
                                          const std::string& sig_algo,
                                          Protocol_Version version) :
-   m_kex_key(0), m_srp_params(0)
+   m_kex_key(nullptr), m_srp_params(nullptr)
    {
    if(buf.size() < 6)
       throw Decoding_Error("Server_Key_Exchange: Packet corrupted");
diff --git a/src/tls/tls_channel.cpp b/src/tls/tls_channel.cpp
index ff6722b5e..dadf26e90 100644
--- a/src/tls/tls_channel.cpp
+++ b/src/tls/tls_channel.cpp
@@ -22,7 +22,7 @@ Channel::Channel(std::function<void (const byte[], size_t)> socket_output_fn,
    proc_fn(proc_fn),
    handshake_fn(handshake_complete),
    writer(socket_output_fn),
-   state(0),
+   state(nullptr),
    handshake_completed(false),
    connection_closed(false),
    m_peer_supports_heartbeats(false),
@@ -33,7 +33,7 @@ Channel::Channel(std::function<void (const byte[], size_t)> socket_output_fn,
 Channel::~Channel()
    {
    delete state;
-   state = 0;
+   state = nullptr;
    }
 
 size_t Channel::received_data(const byte buf[], size_t buf_size)
@@ -105,7 +105,7 @@ size_t Channel::received_data(const byte buf[], size_t buf_size)
 
             alert_notify(alert_msg);
 
-            proc_fn(0, 0, alert_msg);
+            proc_fn(nullptr, 0, alert_msg);
 
             if(alert_msg.type() == Alert::CLOSE_NOTIFY)
                {
@@ -120,7 +120,7 @@ size_t Channel::received_data(const byte buf[], size_t buf_size)
                connection_closed = true;
 
                delete state;
-               state = 0;
+               state = nullptr;
 
                writer.reset();
                reader.reset();
@@ -238,7 +238,7 @@ void Channel::send_alert(const Alert& alert)
       connection_closed = true;
 
       delete state;
-      state = 0;
+      state = nullptr;
 
       writer.reset();
       }
diff --git a/src/tls/tls_channel.h b/src/tls/tls_channel.h
index 46dafc416..fc0595064 100644
--- a/src/tls/tls_channel.h
+++ b/src/tls/tls_channel.h
@@ -69,7 +69,7 @@ class BOTAN_DLL Channel
       /**
       * Attempt to send a heartbeat message (if negotiated with counterparty)
       */
-      void heartbeat() { heartbeat(0, 0); }
+      void heartbeat() { heartbeat(nullptr, 0); }
 
       /**
       * @return certificate chain of the peer (may be empty)
diff --git a/src/tls/tls_client.cpp b/src/tls/tls_client.cpp
index feb9ef85f..1ca256f3e 100644
--- a/src/tls/tls_client.cpp
+++ b/src/tls/tls_client.cpp
@@ -132,7 +132,7 @@ void Client::alert_notify(const Alert& alert)
       if(handshake_completed && state)
          {
          delete state;
-         state = 0;
+         state = nullptr;
          }
       }
    }
@@ -143,7 +143,7 @@ void Client::alert_notify(const Alert& alert)
 void Client::process_handshake_msg(Handshake_Type type,
                                    const std::vector<byte>& contents)
    {
-   if(state == 0)
+   if(!state)
       throw Unexpected_Message("Unexpected handshake message from server");
 
    if(type == HELLO_REQUEST)
@@ -157,7 +157,7 @@ void Client::process_handshake_msg(Handshake_Type type,
       if(!secure_renegotiation.supported() && policy.require_secure_renegotiation())
          {
          delete state;
-         state = 0;
+         state = nullptr;
 
          // RFC 5746 section 4.2
          send_alert(Alert(Alert::NO_RENEGOTIATION));
@@ -474,7 +474,7 @@ void Client::process_handshake_msg(Handshake_Type type,
          session_manager.remove_entry(session_info.session_id());
 
       delete state;
-      state = 0;
+      state = nullptr;
       handshake_completed = true;
       }
    else
diff --git a/src/tls/tls_extensions.cpp b/src/tls/tls_extensions.cpp
index 0f4e3176e..df25c40a5 100644
--- a/src/tls/tls_extensions.cpp
+++ b/src/tls/tls_extensions.cpp
@@ -49,7 +49,7 @@ Extension* make_extension(TLS_Data_Reader& reader,
          return new Session_Ticket(reader, size);
 
       default:
-         return 0; // not known
+         return nullptr; // not known
       }
    }
 
diff --git a/src/tls/tls_extensions.h b/src/tls/tls_extensions.h
index 885851c95..542ac0a82 100644
--- a/src/tls/tls_extensions.h
+++ b/src/tls/tls_extensions.h
@@ -351,7 +351,7 @@ class Extensions
 
          if(i != extensions.end())
             return dynamic_cast<T*>(i->second);
-         return 0;
+         return nullptr;
          }
 
       void add(Extension* extn)
diff --git a/src/tls/tls_handshake_state.cpp b/src/tls/tls_handshake_state.cpp
index b8f3125c8..90de7c3f9 100644
--- a/src/tls/tls_handshake_state.cpp
+++ b/src/tls/tls_handshake_state.cpp
@@ -82,24 +82,24 @@ u32bit bitmask_for_handshake_type(Handshake_Type type)
 */
 Handshake_State::Handshake_State(Handshake_Reader* reader)
    {
-   client_hello = 0;
-   server_hello = 0;
-   server_certs = 0;
-   server_kex = 0;
-   cert_req = 0;
-   server_hello_done = 0;
-   next_protocol = 0;
-   new_session_ticket = 0;
-
-   client_certs = 0;
-   client_kex = 0;
-   client_verify = 0;
-   client_finished = 0;
-   server_finished = 0;
+   client_hello = nullptr;
+   server_hello = nullptr;
+   server_certs = nullptr;
+   server_kex = nullptr;
+   cert_req = nullptr;
+   server_hello_done = nullptr;
+   next_protocol = nullptr;
+   new_session_ticket = nullptr;
+
+   client_certs = nullptr;
+   client_kex = nullptr;
+   client_verify = nullptr;
+   client_finished = nullptr;
+   server_finished = nullptr;
 
    m_handshake_reader = reader;
 
-   server_rsa_kex_key = 0;
+   server_rsa_kex_key = nullptr;
 
    m_version = Protocol_Version::SSL_V3;
 
diff --git a/src/tls/tls_messages.h b/src/tls/tls_messages.h
index e3bdaa6a0..31c35d901 100644
--- a/src/tls/tls_messages.h
+++ b/src/tls/tls_messages.h
@@ -414,7 +414,7 @@ class Server_Key_Exchange : public Handshake_Message
                           const Policy& policy,
                           Credentials_Manager& creds,
                           RandomNumberGenerator& rng,
-                          const Private_Key* signing_key = 0);
+                          const Private_Key* signing_key = nullptr);
 
       Server_Key_Exchange(const std::vector<byte>& buf,
                           const std::string& kex_alg,
diff --git a/src/tls/tls_server.cpp b/src/tls/tls_server.cpp
index 7c2c4d323..241215d59 100644
--- a/src/tls/tls_server.cpp
+++ b/src/tls/tls_server.cpp
@@ -163,7 +163,7 @@ std::map<std::string, std::vector<X509_Certificate> >
 get_server_certs(const std::string& hostname,
                  Credentials_Manager& creds)
    {
-   const char* cert_types[] = { "RSA", "DSA", "ECDSA", 0 };
+   const char* cert_types[] = { "RSA", "DSA", "ECDSA", nullptr };
 
    std::map<std::string, std::vector<X509_Certificate> > cert_chains;
 
@@ -223,7 +223,7 @@ void Server::alert_notify(const Alert& alert)
       if(handshake_completed && state)
          {
          delete state;
-         state = 0;
+         state = nullptr;
          }
       }
    }
@@ -249,7 +249,7 @@ void Server::read_handshake(byte rec_type,
 void Server::process_handshake_msg(Handshake_Type type,
                                    const std::vector<byte>& contents)
    {
-   if(state == 0)
+   if(!state)
       throw Unexpected_Message("Unexpected handshake message from client");
 
    state->confirm_transition_to(type);
@@ -432,7 +432,7 @@ void Server::process_handshake_msg(Handshake_Type type,
                                                   cert_chains[sig_algo]);
             }
 
-         Private_Key* private_key = 0;
+         Private_Key* private_key = nullptr;
 
          if(kex_algo == "RSA" || sig_algo != "")
             {
@@ -608,7 +608,7 @@ void Server::process_handshake_msg(Handshake_Type type,
                                   state->server_finished);
 
       delete state;
-      state = 0;
+      state = nullptr;
       handshake_completed = true;
       }
    else
diff --git a/src/utils/dyn_load/dyn_load.cpp b/src/utils/dyn_load/dyn_load.cpp
index 06b8c5df3..51afb1afe 100644
--- a/src/utils/dyn_load/dyn_load.cpp
+++ b/src/utils/dyn_load/dyn_load.cpp
@@ -30,7 +30,7 @@ void raise_runtime_loader_exception(const std::string& lib_name,
 
 Dynamically_Loaded_Library::Dynamically_Loaded_Library(
    const std::string& library) :
-   lib_name(library), lib(0)
+   lib_name(library), lib(nullptr)
    {
 #if defined(BOTAN_TARGET_OS_HAS_DLOPEN)
    lib = ::dlopen(lib_name.c_str(), RTLD_LAZY);
@@ -60,7 +60,7 @@ Dynamically_Loaded_Library::~Dynamically_Loaded_Library()
 
 void* Dynamically_Loaded_Library::resolve_symbol(const std::string& symbol)
    {
-   void* addr = 0;
+   void* addr = nullptr;
 
 #if defined(BOTAN_TARGET_OS_HAS_DLOPEN)
    addr = ::dlsym(lib, symbol.c_str());