Re: Testing build failure with latest GCC

[Steve Ellcey <sellcey@cavium.com>]

On Thu, 2017-05-25 at 18:56 +0200, Florian Weimer wrote:
> On Thu, May 25, 2017 at 6:50 PM, Steve Ellcey <sellcey@cavium.com>
> wrote:
> > 
> > I am building the top-of-tree glibc with top-of-tree gcc and getting
> > these messages when running 'make check'.  Should we explicitly ignore
> > the return value of fgets in these tests or check it and set 'failed'
> > if it is not the expected value?  Or do we think GCC is at fault?  It
> > seems like a legimate warning and we do compile with -Wall -Werror.
> Any idea why it didn't warn before?

No I don't know why it didn't warn before.  I assume it is a recent GCC
change but I don't know what change.  I'll see if I can track down a
specific change that caused this to start.

> The f* stream functions are special. You can check for errors using
> the return value, or using ferror. Therefore, the attribute might not
> be correct.
> 
> Considering how difficult is to bypass warn-used attribute (a cast to
> void is not enough), I wonder if we should drop the attribute.

That is a good point, I thought a '(void)' cast could fix this but I
see that it does not.

Steve Ellcey