src: add wrapper for process.emitWarning()

PR-URL: https://github.com/nodejs/node/pull/9139
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>

src/node.cc

@@ -2609,6 +2609,33 @@ void ClearFatalExceptionHandlers(Environment* env) {
       Undefined(env->isolate())).FromJust();
 }
 
+// Call process.emitWarning(str), fmt is a snprintf() format string
+void ProcessEmitWarning(Environment* env, const char* fmt, ...) {
+  char warning[1024];
+  va_list ap;
+
+  va_start(ap, fmt);
+  vsnprintf(warning, sizeof(warning), fmt, ap);
+  va_end(ap);
+
+  HandleScope handle_scope(env->isolate());
+  Context::Scope context_scope(env->context());
+
+  Local<Object> process = env->process_object();
+  MaybeLocal<Value> emit_warning = process->Get(env->context(),
+      FIXED_ONE_BYTE_STRING(env->isolate(), "emitWarning"));
+  Local<Value> arg = node::OneByteString(env->isolate(), warning);
+
+  Local<Value> f;
+
+  if (!emit_warning.ToLocal(&f)) return;
+  if (!f->IsFunction()) return;
+
+  // MakeCallback() unneeded, because emitWarning is internal code, it calls
+  // process.emit('warning', ..), but does so on the nextTick.
+  f.As<v8::Function>()->Call(process, 1, &arg);
+}
+
 
 static void Binding(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);

src/node_internals.h

@@ -133,6 +133,8 @@ void AppendExceptionLine(Environment* env,
 
 NO_RETURN void FatalError(const char* location, const char* message);
 
+void ProcessEmitWarning(Environment* env, const char* fmt, ...);
+
 v8::Local<v8::Value> BuildStatsObject(Environment* env, const uv_stat_t* s);
 
 enum Endianness {