child_process: fix segfault after failed spawn

The process handle is uninitialized when uv_spawn() fails so don't export the
handle to JS land when that happens. Attempts to close the uninitialized handle
resulted in segmentation faults and memory corruption.

Fixes #2481.

src/process_wrap.cc

@@ -177,10 +177,14 @@ class ProcessWrap : public HandleWrap {
 
  int r = uv_spawn(uv_default_loop(), &wrap->process_, options);
 
- wrap->SetHandle((uv_handle_t*)&wrap->process_);
- assert(wrap->process_.data == wrap);
-
- wrap->object_->Set(String::New("pid"), Integer::New(wrap->process_.pid));
+ if (r) {
+ SetErrno(uv_last_error(uv_default_loop()));
+ }
+ else {
+ wrap->SetHandle((uv_handle_t*)&wrap->process_);
+ assert(wrap->process_.data == wrap);
+ wrap->object_->Set(String::New("pid"), Integer::New(wrap->process_.pid));
+ }
 
  if (options.args) {
  for (int i = 0; options.args[i]; i++) free(options.args[i]);
@@ -195,8 +199,6 @@ class ProcessWrap : public HandleWrap {
  delete [] options.env;
  }
 
- if (r) SetErrno(uv_last_error(uv_default_loop()));
-
  return scope.Close(Integer::New(r));
  }