Add BOTAN_WARN_UNUSED_RESULT macro

Only works for GCC and Clang

3 files changed, 19 insertions, 13 deletions

diff --git a/src/build-data/buildh.in b/src/build-data/buildh.in
index fea18fd90..56b70e060 100644
--- a/src/build-data/buildh.in
+++ b/src/build-data/buildh.in
@@ -201,6 +201,12 @@ Each read generates 32 bits of output
   #define BOTAN_FUNC_ISA(isa)
 #endif
 
+#if defined(__GNUG__) || defined(__clang__)
+  #define BOTAN_WARN_UNUSED_RESULT __attribute__ ((warn_unused_result))
+#else
+  #define BOTAN_WARN_UNUSED_RESULT
+#endif
+
 /*
 * Compile-time deprecation warnings
 */
diff --git a/src/lib/filters/pipe.h b/src/lib/filters/pipe.h
index 286484a81..8775e1433 100644
--- a/src/lib/filters/pipe.h
+++ b/src/lib/filters/pipe.h
@@ -134,7 +134,7 @@ class BOTAN_DLL Pipe final : public DataSource
       * for which the information is desired
       * @return number of bytes that can still be read
       */
-      size_t remaining(message_id msg = DEFAULT_MESSAGE) const;
+      size_t remaining(message_id msg = DEFAULT_MESSAGE) const BOTAN_WARN_UNUSED_RESULT;
 
       /**
       * Read the default message from the pipe. Moves the internal
@@ -145,7 +145,7 @@ class BOTAN_DLL Pipe final : public DataSource
       * @param length the length of the byte array output
       * @return number of bytes actually read into output
       */
-      size_t read(byte output[], size_t length) override;
+      size_t read(byte output[], size_t length) override BOTAN_WARN_UNUSED_RESULT;
 
       /**
       * Read a specified message from the pipe. Moves the internal
@@ -156,7 +156,7 @@ class BOTAN_DLL Pipe final : public DataSource
       * @param msg the number identifying the message to read from
       * @return number of bytes actually read into output
       */
-      size_t read(byte output[], size_t length, message_id msg);
+      size_t read(byte output[], size_t length, message_id msg) BOTAN_WARN_UNUSED_RESULT;
 
       /**
       * Read a single byte from the pipe. Moves the internal offset so
@@ -167,23 +167,24 @@ class BOTAN_DLL Pipe final : public DataSource
       * @param msg the message to read from
       * @return number of bytes actually read into output
       */
-      size_t read(byte& output, message_id msg = DEFAULT_MESSAGE);
+      size_t read(byte& output, message_id msg = DEFAULT_MESSAGE) BOTAN_WARN_UNUSED_RESULT;
 
       /**
       * Read the full contents of the pipe.
       * @param msg the number identifying the message to read from
       * @return secure_vector holding the contents of the pipe
       */
-      secure_vector<byte> read_all(message_id msg = DEFAULT_MESSAGE);
+      secure_vector<byte> read_all(message_id msg = DEFAULT_MESSAGE) BOTAN_WARN_UNUSED_RESULT;
 
       /**
       * Read the full contents of the pipe.
       * @param msg the number identifying the message to read from
       * @return string holding the contents of the pipe
       */
-      std::string read_all_as_string(message_id = DEFAULT_MESSAGE);
+      std::string read_all_as_string(message_id = DEFAULT_MESSAGE) BOTAN_WARN_UNUSED_RESULT;
 
-      /** Read from the default message but do not modify the internal
+      /**
+      * Read from the default message but do not modify the internal
       * offset. Consecutive calls to peek() will return portions of
       * the message starting at the same position.
       * @param output the byte array to write the peeked message part to
@@ -191,7 +192,7 @@ class BOTAN_DLL Pipe final : public DataSource
       * @param offset the offset from the current position in message
       * @return number of bytes actually peeked and written into output
       */
-      size_t peek(byte output[], size_t length, size_t offset) const override;
+      size_t peek(byte output[], size_t length, size_t offset) const override BOTAN_WARN_UNUSED_RESULT;
 
       /** Read from the specified message but do not modify the
       * internal offset. Consecutive calls to peek() will return
@@ -203,7 +204,7 @@ class BOTAN_DLL Pipe final : public DataSource
       * @return number of bytes actually peeked and written into output
       */
       size_t peek(byte output[], size_t length,
-                  size_t offset, message_id msg) const;
+                  size_t offset, message_id msg) const BOTAN_WARN_UNUSED_RESULT;
 
       /** Read a single byte from the specified message but do not
       * modify the internal offset. Consecutive calls to peek() will
@@ -214,7 +215,7 @@ class BOTAN_DLL Pipe final : public DataSource
       * @return number of bytes actually peeked and written into output
       */
       size_t peek(byte& output, size_t offset,
-                  message_id msg = DEFAULT_MESSAGE) const;
+                  message_id msg = DEFAULT_MESSAGE) const BOTAN_WARN_UNUSED_RESULT;
 
       /**
       * @return the number of bytes read from the default message.
diff --git a/src/lib/utils/data_src.h b/src/lib/utils/data_src.h
index b24fd75a4..299a42ab5 100644
--- a/src/lib/utils/data_src.h
+++ b/src/lib/utils/data_src.h
@@ -30,7 +30,7 @@ class BOTAN_DLL DataSource
       * @return length in bytes that was actually read and put
       * into out
       */
-      virtual size_t read(byte out[], size_t length) = 0;
+      virtual size_t read(byte out[], size_t length) BOTAN_WARN_UNUSED_RESULT = 0;
 
       virtual bool check_available(size_t n) = 0;
 
@@ -45,8 +45,7 @@ class BOTAN_DLL DataSource
       * @return length in bytes that was actually read and put
       * into out
       */
-      virtual size_t peek(byte out[], size_t length,
-                          size_t peek_offset) const = 0;
+      virtual size_t peek(byte out[], size_t length, size_t peek_offset) const BOTAN_WARN_UNUSED_RESULT = 0;
 
       /**
       * Test whether the source still has data that can be read.