1665026 - Prevent ToResultInvoke from being instantiated with a raw pointer result type

Status: RESOLVED FIXED

(Core :: MFBT, task)

Description

[Simon Giesecke [:sg] [he/him]]

The following would produce a leak, since the result type with be Result<nsIFile*, nsresult>:

bool DoIt(nsIFile& aFile) {
  auto res = ToResultInvoke(std::mem_fn(&nsIFIle::Clone), aFile);
  return res.isOk();
}

The correct way to do this would be to specify explicitly that a smart pointer should be the result type:

void DoIt(nsIFile& aFile) {
  auto res = ToResultInvoke<nsCOMPtr<nsIFile>>(std::mem_fn(&nsIFIle::Clone), aFile);
  return res.isOk();
}

The former variant should therefore be prevented from being instantiated.

Note that this also prevents ToResultInvoke to be used with non-owning raw pointer output parameters, but XPCOM conventions do not allow this, at least not for ref-counted types.

Comment 1

[Simon Giesecke [:sg] [he/him]]

Attachment: Bug 1665026 - Prevent ToResultInvoke from being instantiated with a raw pointer result type.

Depends on D90234

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/dd6db9d9349c
Prevent ToResultInvoke from being instantiated with a raw pointer result type. r=janv

Comment 3

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/dd6db9d9349c