Closures do not report their class in stack traces

[Ocramius]

debug_backtrace() does not report the class that a particular Closure instance is bound to:

<?php

class Foo {
    public function bar() {
        $cb = function () {
            var_dump(debug_backtrace()[0]['class']);
        };

        $cb();
    }
}

(new Foo)->bar();

Example: http://3v4l.org/L1J8V (also verified on current master)

This makes it quite hard to emulate scope access limitations in userland.

[Ocramius]

After further inspection, I found the bits of code that require action, but I don't really know where to look to make all this happen:

• hhvm/hphp/runtime/base/backtrace.cpp

  Line 204 in cbeea88

  if (ctx != nullptr && !fp->m_func->isClosureBody()) {

  - && !fp->m_func->isClosureBody() must be removed

• hhvm/hphp/runtime/vm/bytecode.cpp

  Lines 173 to 178 in cbeea88

  	Class* arGetContextClassImpl<false>(const ActRec* ar) {
  	if (ar == nullptr) {
  	return nullptr;
  	}
  	return ar->m_func->cls();
  	}

  must be capable to extract closure bound class, something like following pseudo-code:

  template <>
  Class* arGetContextClassImpl<false>(const ActRec* ar) {
    if (ar == nullptr) {
      return nullptr;
    }
  
    if (ar->m_func->isClosureBody()) {
      // incomplete (probably wrong right now) - need to get a reference to the closure itself first
      return ActRec::decodeClass(ar->getThisOrClass());
    }
  
    return ar->m_func->cls();
  }

[paulbiss]

The ActRec may contain a this rather than a class so you'll need to check for that and extract the class from the ObjectData if it isn't a static closure, it may also contain neither. Also note that this will give you the bound class which may not even be related to the declaring class. It may also be different from the scope class. Lastly arGetContextClassImpl should probably return the scope class not the bound class, so you should make your changes in backtrace.cpp and leave that function alone.

[Ocramius]

and leave that function alone

Actually a good hint, as arGetContextClassImpl() is probably used in a lot of other contexts

[Ocramius]

Another detail that slipped through is that also key 'object' is missing: http://3v4l.org/q0Cqj

[Ocramius]

Any news on this? Pretty much blocked by it for building Doctrine3 prototypes :-(