[c++] Use memcpy to type pun; fix alias violations

We now use memcpy to pun from one type to another, avoiding aliasing
violations as well as alignment errors. x86-like chips never failed due
to the alignment errors, but others, like some ARM chips, did. This
should also fix emscripten cross-compilation.

Fixes microsoft#305

CHANGELOG.md

@@ -35,6 +35,10 @@ different versioning scheme, following the Haskell community's
 * Eliminate need for warning suppression on MSVC14 via warning.h in Bond
   itself. warning.h is still in place on MSVC12; furthermore, we don't alter
   warning.h for now as it may be depended upon by application code.
+* Avoid unaligned memory access on non-x86/x64 platforms.
+  [Issue #305](https://github.com/Microsoft/bond/issues/305)
+* Improve compliance with strict-aliasing rules.
+    * Bond now builds on Clang/GCC with `-fstrict-aliasing`.
 
 ## C# ###
 

cmake/Config.cmake

@@ -114,6 +114,7 @@ add_definitions (-D_ENABLE_ATOMIC_ALIGNMENT_FIX)
 
 cxx_add_compile_options(Clang
     -fPIC
+    -fstrict-aliasing
     --std=c++11
     -Wall
     -Werror
@@ -122,6 +123,7 @@ cxx_add_compile_options(Clang
 
 cxx_add_compile_options(AppleClang
     -fPIC
+    -fstrict-aliasing
     --std=c++11
     -Wall
     -Werror
@@ -130,6 +132,7 @@ cxx_add_compile_options(AppleClang
 
 cxx_add_compile_options(GNU
     -fPIC
+    -fstrict-aliasing
     --std=c++11
     -Wall
     -Werror

cpp/inc/bond/protocol/compact_binary.h

@@ -10,6 +10,8 @@
 #include <bond/stream/output_counter.h>
 #include <boost/call_traits.hpp>
 #include <boost/noncopyable.hpp>
+#include <boost/static_assert.hpp>
+#include <cstring>
 
 /*
 
@@ -224,14 +226,18 @@ class CompactBinaryReader
 
         if (id == (0x07 << 5))
         {
+            // ID is in (0xff, 0xffff] and is in the next two bytes
             _input.Read(id);
         }
         else if (id == (0x06 << 5))
         {
-            _input.Read(reinterpret_cast<uint8_t&>(id));
+            // ID is in (5, 0xff] and is in the next one byte
+            _input.Read(raw);
+            id = static_cast<uint16_t>(raw);
         }
         else
         {
+            // ID is in [0, 5] and was in the byte we already read
             id >>= 5;
         }
     }
@@ -310,7 +316,9 @@ class CompactBinaryReader
     Read(T& value)
     {
         BOOST_STATIC_ASSERT(sizeof(value) == sizeof(int32_t));
-        Read(*reinterpret_cast<int32_t*>(&value));
+        int32_t raw;
+        Read(raw);
+        std::memcpy(&value, &raw, sizeof(raw));
     }
 
 

cpp/inc/bond/protocol/random_protocol.h

@@ -6,9 +6,8 @@
 #include <bond/core/containers.h>
 #include <bond/core/blob.h>
 #include <bond/core/traits.h>
-
-#include <cstring>
 #include <boost/static_assert.hpp>
+#include <cstring>
 
 namespace bond
 {
@@ -116,6 +115,8 @@ class RandomProtocolReader
 
     void Read(double& value)
     {
+        BOOST_STATIC_ASSERT(sizeof(double) == sizeof(uint64_t));
+
         uint8_t sign;
         uint8_t exponent;
         uint32_t mantissa;
@@ -129,12 +130,13 @@ class RandomProtocolReader
             exponent = 0x80;
 
         uint64_t bits = ((uint64_t)(sign) << 63) | ((uint64_t)(exponent) << (52 + 3)) | (uint64_t)mantissa;
-
-        *reinterpret_cast<uint64_t*>(&value) = bits;
+        std::memcpy(&value, &bits, sizeof(bits));
     }
 
     void Read(float& value)
     {
+        BOOST_STATIC_ASSERT(sizeof(float) == sizeof(uint32_t));
+
         uint8_t sign;
         uint8_t exponent;
         uint16_t mantissa;
@@ -148,8 +150,7 @@ class RandomProtocolReader
             exponent = 0x80;
 
         uint32_t bits = ((uint32_t)(sign) << 31) | ((uint32_t)(exponent) << 23) | (uint32_t)mantissa;
-
-        *reinterpret_cast<uint32_t*>(&value) = bits;
+        std::memcpy(&value, &bits, sizeof(bits));
     }
 
     template <typename T>

cpp/inc/bond/stream/input_buffer.h

@@ -5,7 +5,9 @@
 
 #include <bond/core/blob.h>
 #include <bond/core/exception.h>
+#include <bond/core/traits.h>
 #include <boost/static_assert.hpp>
+#include <cstring>
 
 namespace bond
 {
@@ -21,7 +23,7 @@ struct VariableUnsignedUnchecked
     {
         T byte = *p++;
         value |= (byte & 0x7f) << Shift;
-        
+
         if (byte >= 0x80)
             VariableUnsignedUnchecked<T, Shift + 7>::Read(p, value);
     }
@@ -36,7 +38,7 @@ struct VariableUnsignedUnchecked<T, 0>
     {
         T byte = *p++;
         value = (byte & 0x7f);
-        
+
         if (byte >= 0x80)
             VariableUnsignedUnchecked<T, 7>::Read(p, value);
     }
@@ -84,14 +86,14 @@ struct VariableUnsignedUnchecked<uint64_t, 56>
 }
 
 /// @brief Memory backed input stream
-class InputBuffer 
+class InputBuffer
 {
 public:
     /// @brief Default constructor
     InputBuffer()
         : _pointer()
     {}
-    
+
     /// @brief Construct from a blob
     ///
     /// InputBuffer makes a copy of the blob. Assuming that the blob was
@@ -106,7 +108,7 @@ class InputBuffer
     ///
     /// Pointer(s) to the memory buffer may be held by the objects deserialized
     /// from the stream. It is the application's responsibility to manage
-    /// the lifetime of the memory buffer appropriately. 
+    /// the lifetime of the memory buffer appropriately.
     InputBuffer(const void* buffer, uint32_t length)
         : _blob(buffer, length),
           _pointer()
@@ -126,38 +128,42 @@ class InputBuffer
         {
             EofException(sizeof(uint8_t));
         }
-        
+
         value = static_cast<const uint8_t>(_blob.content()[_pointer++]);
     }
 
-    
+
     template <typename T>
     void Read(T& value)
     {
+        BOOST_STATIC_ASSERT(bond::is_arithmetic<T>::value || bond::is_enum<T>::value);
+
         if (sizeof(T) > _blob.length() - _pointer)
         {
             EofException(sizeof(T));
         }
-
-        value = *reinterpret_cast<const T*>(_blob.content() + _pointer);
+
+        const void* const src = _blob.content() + _pointer;
+        std::memcpy(&value, src, sizeof(T));
 
         _pointer += sizeof(T);
     }
 
-    
+
     void Read(void *buffer, uint32_t size)
     {
         if (size > _blob.length() - _pointer)
         {
             EofException(size);
         }
 
-        ::memcpy(buffer, _blob.content() + _pointer, size);
+        const void* const src = _blob.content() + _pointer;
+        std::memcpy(buffer, src, size);
 
         _pointer += size;
     }
 
-    
+
     void Read(blob& blob, uint32_t size)
     {
         if (size > _blob.length() - _pointer)
@@ -170,14 +176,14 @@ class InputBuffer
         _pointer += size;
     }
 
-    
-    void Skip(uint32_t size) 
+
+    void Skip(uint32_t size)
     {
         if (size > _blob.length() - _pointer)
         {
             return;
         }
-        
+
         _pointer += size;
     }
 
@@ -202,7 +208,7 @@ class InputBuffer
             GenericReadVariableUnsigned(*this, value);
         }
     }
-    
+
 protected:
     void EofException(uint32_t size) const
     {