Request for a new compiler warning for moved objects

[Sean]

Is it possible to add a compiler warning when calling methods on objects that have been moved.  Especially in a function call?  I've been bitten by this a few times now.

Throws SIGSEGV:

std::unique_ptr<Thingy> smart_ptr = ...;

...

delegate_->Resolve(

  smart_ptr->bar(),

  base::Bind(&Handler::OnResolveHandled,

                      weak_factory_.GetWeakPtr(), base::Passed(&smart_ptr)));

FIXED:

std::unique_ptr<Thingy> smart_ptr = ...;

...

const Bar& ref = smart_ptr->bar();

delegate_->Resolve(

  ref,

  base::Bind(&Handler::OnResolveHandled,

                      weak_factory_.GetWeakPtr(), base::Passed(&smart_ptr)));

The cause of this is that there's no required ordering for the evaluation of function parameters.  So, smart_ptr is moved before smart_ptr->bar() is evaluated.  So, smart_ptr->bar() might cause a segfault.

[Nick Maniscalco]

Sean, this sounds related to https://bugs.chromium.org/p/chromium/issues/detail?id=409318

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[Nico Weber]

Yup; also see https://llvm.org/bugs/show_bug.cgi?id=20819 Let me know if you're interested in working on this :-)

[Sean Kau]

yep.  That's definitely the right bug.  Would I be interested? yes.  Do I have time?  Probably not.  :(

[Sean]

If anybody ends up picking this up, this is an update to llvm's use-after-move detection:

https://reviews.llvm.org/D25612

[CJ Dimeglio]

Im looking into it now.