Re: [PATCH/RFC 0/3] compiling git with gcc -O3 -Wuninitialized

From: Jeff King <peff@peff.net>
Date: Dec 15, 2012, 10:09 UTC
Message-ID: <20121215100954.GA21577@sigill.intra.peff.net>
In-Reply-To: <CACsJy8BqOEvEHy7i89fKSgQH5kUYFWvchJwD_fQsYjagrh+X2w@mail.gmail.com>

On Sat, Dec 15, 2012 at 10:07:54AM +0700, Nguyen Thai Ngoc Duy wrote:

Show 12 quoted lines

> > If get_foo() is not inlined, then when compiling some_fun, gcc sees only
> > that a pointer to the local variable is passed, and must assume that it
> > is an out parameter that is initialized after get_foo returns.
> >
> > However, when get_foo() is inlined, the compiler may look at all of the
> > code together and see that some code paths in get_foo() do not
> > initialize the variable. And we get the extra warnings.
> 
> Other options:
> 
>  - Any __attribute__ or #pragma to aid flow analysis (or would gcc dev be
>    willing to add one)?

I looked through the full list of __attribute__ flags and couldn't find anything that would help.

>  - Maintain a list of false positives and filter them out from gcc output?

I think it would be just as simple to use the "int foo = foo" hack, which accomplishes the same thing without any post-processing step.

> And if we do this, should we support other compilers as well? I tried
> clang once a long while ago and got a bunch of warnings iirc.

I don't use clang myself, but I don't have any problem with other people submitting patches to clean up its warnings, provided they don't make the code harder to read or write.

-Peff