[wasm] Enforce strict ordering of WASM module sections.

src/wasm/wasm-module.h

Index: src/wasm/wasm-module.h
diff --git a/src/wasm/wasm-module.h b/src/wasm/wasm-module.h
index 4e5aa7848605cddd3c8597434a9b97fab9174688..45969bc705bd391dc7ef583d0969aba57e053971 100644
--- a/src/wasm/wasm-module.h
+++ b/src/wasm/wasm-module.h
@@ -29,20 +29,20 @@ const uint32_t kWasmVersion = 0x0a;
 // internally V8 uses an enum to handle them.
 //
 // Entries have the form F(enumerator, string).

[JF, 2016/04/19 15:48:47]

Update doc on F.

[titzer, 2016/04/20 08:51:24]

Done.

-#define FOR_EACH_WASM_SECTION_TYPE(F)          \
-  F(Memory, "memory")                          \
-  F(Signatures, "signatures")                  \
-  F(Functions, "functions")                    \
-  F(Globals, "globals")                        \
-  F(DataSegments, "data_segments")             \
-  F(FunctionTable, "function_table")           \
-  F(End, "end")                                \
-  F(StartFunction, "start_function")           \
-  F(ImportTable, "import_table")               \
-  F(ExportTable, "export_table")               \
-  F(FunctionSignatures, "function_signatures") \
-  F(FunctionBodies, "function_bodies")         \
-  F(Names, "names")
+#define FOR_EACH_WASM_SECTION_TYPE(F)             \
+  F(Signatures, 1, "signatures")                  \
+  F(ImportTable, 2, "import_table")               \
+  F(FunctionSignatures, 3, "function_signatures") \
+  F(FunctionTable, 4, "function_table")           \
+  F(Memory, 5, "memory")                          \
+  F(ExportTable, 6, "export_table")               \
+  F(StartFunction, 7, "start_function")           \
+  F(FunctionBodies, 8, "function_bodies")         \
+  F(DataSegments, 9, "data_segments")             \
+  F(Names, 10, "names")                           \
+  F(Globals, 0, "globals")                        \
+  F(Functions, 0, "functions")                    \
+  F(End, 0, "end")

[JF, 2016/04/19 15:48:47]

I'm not sure I understand orders: the non-zero ones have to follow each other,
but globals / functions / end ca appear anywhere, and repeat as much as they
want?

[titzer, 2016/04/20 08:51:24]

That's right. The 0-value sections are V8-internal/legacy sections. (We should
also probably rename the V8-only sections: later).

 
 // Contants for the above section types: {LEB128 length, characters...}.
 #define WASM_SECTION_MEMORY 6, 'm', 'e', 'm', 'o', 'r', 'y'
@@ -85,7 +85,7 @@ const uint32_t kWasmVersion = 0x0a;
 
 struct WasmSection {
   enum class Code : uint32_t {
-#define F(enumerator, string) enumerator,
+#define F(enumerator, order, string) enumerator,
     FOR_EACH_WASM_SECTION_TYPE(F)
 #undef F
         Max
@@ -94,7 +94,9 @@ struct WasmSection {
   static WasmSection::Code end();
   static WasmSection::Code next(WasmSection::Code code);
   static const char* getName(Code code);
+  static int getOrder(Code code);
   static size_t getNameLength(Code code);
+  static WasmSection::Code lookup(const byte* string, uint32_t length);
 };
 
 enum WasmFunctionDeclBit {