Fix wrong endianness of wasm header in WasmModuleWriter on big-endian platforms

src/wasm/encoder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/signature.h"
 
 #include "src/handles.h"
 #include "src/v8.h"
 #include "src/zone-containers.h"
 
 #include "src/wasm/ast-decoder.h"
 #include "src/wasm/encoder.h"
 #include "src/wasm/leb-helper.h"
+#include "src/wasm/wasm-external-refs.h"
 #include "src/wasm/wasm-macro-gen.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-opcodes.h"
 
 #include "src/v8memory.h"
 
 #if DEBUG
 #define TRACE(...)                                    \
   do {                                                \
     if (FLAG_trace_wasm_encoder) PrintF(__VA_ARGS__); \
@@ skipping 267 matching lines @@
       data_segments_(zone),
       signatures_(zone),
       indirect_functions_(zone),
       globals_(zone) {}
 
 void WasmModuleWriter::WriteTo(ZoneBuffer& buffer) const {
   uint32_t exports = 0;
 
   // == Emit magic =============================================================
   TRACE("emit magic\n");
-  buffer.write_u32(kWasmMagic);
-  buffer.write_u32(kWasmVersion);
+  buffer.write_u32(word32_to_little_endianness(&kWasmMagic));

[titzer, 2016/05/27 10:47:27]

What about instead making the write_u32 function always write little endian, and
forgoing the byte swap routines, similar to how the decoder always reads little
endian?

[ivica.bogosavljevic, 2016/05/27 12:23:24]

Say no more!

+  buffer.write_u32(word32_to_little_endianness(&kWasmVersion));
 
   // == Emit signatures ========================================================
   if (signatures_.size() > 0) {
     size_t start = EmitSection(WasmSection::Code::Signatures, buffer);
     buffer.write_size(signatures_.size());
 
     for (FunctionSig* sig : signatures_) {
       buffer.write_u8(kWasmFunctionTypeForm);
       buffer.write_size(sig->parameter_count());
       for (size_t j = 0; j < sig->parameter_count(); j++) {
@@ skipping 101 matching lines @@
 
     for (auto segment : data_segments_) {
       segment->Write(buffer);
     }
     FixupSection(buffer, start);
   }
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8