[wasm] Generate correct locations for error messages

src/d8.cc

 // Copyright 2012 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 <errno.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 
 #include <algorithm>
@@ skipping 404 matching lines @@
 ShellOptions Shell::options;
 base::OnceType Shell::quit_once_ = V8_ONCE_INIT;
 
 bool CounterMap::Match(void* key1, void* key2) {
   const char* name1 = reinterpret_cast<const char*>(key1);
   const char* name2 = reinterpret_cast<const char*>(key2);
   return strcmp(name1, name2) == 0;
 }
 
 
-// Converts a V8 value to a C string.
-const char* Shell::ToCString(const v8::String::Utf8Value& value) {
-  return *value ? *value : "<string conversion failed>";
-}
-
-
 ScriptCompiler::CachedData* CompileForCachedData(
     Local<String> source, Local<Value> name,
     ScriptCompiler::CompileOptions compile_options) {
   int source_length = source->Length();
   uint16_t* source_buffer = new uint16_t[source_length];
   source->Write(source_buffer, 0, source_length);
   int name_length = 0;
   uint16_t* name_buffer = NULL;
   if (name->IsString()) {
     Local<String> name_string = Local<String>::Cast(name);
@@ skipping 808 matching lines @@
 
 void Shell::Version(const v8::FunctionCallbackInfo<v8::Value>& args) {
   args.GetReturnValue().Set(
       String::NewFromUtf8(args.GetIsolate(), V8::GetVersion(),
                           NewStringType::kNormal).ToLocalChecked());
 }
 
 
 void Shell::ReportException(Isolate* isolate, v8::TryCatch* try_catch) {
   HandleScope handle_scope(isolate);
-  Local<Context> context;
-  bool enter_context = !isolate->InContext();
+  Local<Context> context = isolate->GetCurrentContext();
+  bool enter_context = context.IsEmpty();
   if (enter_context) {
     context = Local<Context>::New(isolate, evaluation_context_);
     context->Enter();
   }
+  // Converts a V8 value to a C string.
+  auto ToCString = [](const v8::String::Utf8Value& value) {

[titzer, 2016/12/12 11:51:33]

Finally a decent use of C++ lambda!

+    return *value ? *value : "<string conversion failed>";
+  };
+
   v8::String::Utf8Value exception(try_catch->Exception());
   const char* exception_string = ToCString(exception);
   Local<Message> message = try_catch->Message();
   if (message.IsEmpty()) {
     // V8 didn't provide any extra information about this error; just
     // print the exception.
     printf("%s\n", exception_string);
+  } else if (message->GetScriptOrigin().Options().IsWasm()) {
+    // Print <WASM>[(function index)]((function name))+(offset): (message).
+    int function_index = message->GetLineNumber(context).FromJust() - 1;
+    int offset = message->GetStartColumn(context).FromJust();
+    printf("<WASM>[%d]+%d: %s\n", function_index, offset, exception_string);
   } else {
     // Print (filename):(line number): (message).
     v8::String::Utf8Value filename(message->GetScriptOrigin().ResourceName());
     const char* filename_string = ToCString(filename);
-    Maybe<int> maybeline = message->GetLineNumber(isolate->GetCurrentContext());
-    int linenum = maybeline.IsJust() ? maybeline.FromJust() : -1;
+    int linenum = message->GetLineNumber(context).FromMaybe(-1);
     printf("%s:%i: %s\n", filename_string, linenum, exception_string);
     Local<String> sourceline;
-    if (message->GetSourceLine(isolate->GetCurrentContext())
-            .ToLocal(&sourceline)) {
+    if (message->GetSourceLine(context).ToLocal(&sourceline)) {
       // Print line of source code.
       v8::String::Utf8Value sourcelinevalue(sourceline);
       const char* sourceline_string = ToCString(sourcelinevalue);
       printf("%s\n", sourceline_string);
       // Print wavy underline (GetUnderline is deprecated).
-      int start =
-          message->GetStartColumn(isolate->GetCurrentContext()).FromJust();
+      int start = message->GetStartColumn(context).FromJust();
       for (int i = 0; i < start; i++) {
         printf(" ");
       }
-      int end = message->GetEndColumn(isolate->GetCurrentContext()).FromJust();
+      int end = message->GetEndColumn(context).FromJust();
       for (int i = start; i < end; i++) {
         printf("^");
       }
       printf("\n");
     }
-    Local<Value> stack_trace_string;
-    if (try_catch->StackTrace(isolate->GetCurrentContext())
-            .ToLocal(&stack_trace_string) &&
-        stack_trace_string->IsString()) {
-      v8::String::Utf8Value stack_trace(
-          Local<String>::Cast(stack_trace_string));
-      printf("%s\n", ToCString(stack_trace));
-    }
+  }
+  Local<Value> stack_trace_string;
+  if (try_catch->StackTrace(context).ToLocal(&stack_trace_string) &&
+      stack_trace_string->IsString()) {
+    v8::String::Utf8Value stack_trace(Local<String>::Cast(stack_trace_string));
+    printf("%s\n", ToCString(stack_trace));
   }
   printf("\n");
   if (enter_context) context->Exit();
 }
 
 
 int32_t* Counter::Bind(const char* name, bool is_histogram) {
   int i;
   for (i = 0; i < kMaxNameSize - 1 && name[i]; i++)
     name_[i] = static_cast<char>(name[i]);
@@ skipping 1705 matching lines @@
 }
 
 }  // namespace v8
 
 
 #ifndef GOOGLE3
 int main(int argc, char* argv[]) {
   return v8::Shell::Main(argc, argv);
 }
 #endif