[PATCH] D81525: [Support] Ensure errs() is constructed after outs() and don't rerun tie when errs() is called

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added a comment.

In D81525#2088267 <https://reviews.llvm.org/D81525#2088267>, @amaiorano wrote:

> I posted this on the GitHub PR, but was told the main discussion about this bug is here:
>  https://github.com/llvm/llvm-project/commit/1ce831912c797df1cb6d313d8e576a3f86175b6d#r39838454
>
> Not sure a separate InitializeAndTie struct is needed when you can use an immediately-invoked lambda:
>
>   raw_fd_ostream &llvm::errs() {
>     // Set standard error to be unbuffered and tied to outs() by default.
>     static auto S = [] { 
>       raw_fd_ostream s(STDERR_FILENO, false, true);
>       s.tie(&outs());
>       return s;
>     }();
>     return S;
>   }
>
>
> I'm assuming 's' can be returned by value here, of course, otherwise we could make it static and return by reference from the lambda.


A lambda does not work. raw_fd_ostream does not have a copy constructor.

> Unless there is an immediate resolution (and the discussion seems to indicate that it is worth taking our time here), can we revert the patch that introduces a TSAN failure?

@mehdi_amini Pushing this patch will fix the issue.

Can you be more specific about concurrent outs() or outs()+errs() calls?


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