Re: [RFC PATCH] diagnose built-in declarations without prototype (PR 83656)

[Jeff Law <law at redhat dot com>]

On 06/27/2018 09:27 AM, Jakub Jelinek wrote:
> On Wed, Jun 27, 2018 at 09:17:07AM -0600, Jeff Law wrote:
>>> About 115 tests fail due to incompatible declarations of
>>> the built-in functions below (the number shows the number
>>> of warnings for each functions):
>>>
>>> 428   abort
>>>  58   exit
>>>  36   memcpy
>>>  17   memmove
>>>  15   realloc
>>>  14   cabs
>>>   5   strncpy
>>>   4   strcmp
>>>   3   alloca
>>>   2   rindex
>>>   1   aligned_alloc
>> I'm supportive of this change.  Though I'm more worried about the
>> affects on the distros than I am on the testsuite (which I expected to
>> be in worse shape WRT this issue than your analysis indicates).
> 
> I'm mainly worried about configure tests, those will be hit hardest by
> this and might result in silently turning off many features of the compiled
> programs.
It's certainly a concern.  Sadly, it's a hard one to deal with because
we can't just throw code at it and see what complains.  Instead we end
up with packages that don't configure in the appropriate features.

I think when Roland and I discussed this in the context of gold the
thing we sketched out was to build the distro, capturing the resultant
config.h, then rebuild with gold, capture the new config.h and compare.

We never actually tried that -- we didn't green light the gold
transition due to other reasons.

Just wandering around our own configury bits does show some of these
kinds of problems.  No idea if they'd manifest themselves in a visible
ways though.

Maybe it's a case where it's an opt-in argument in the immediate term
and we work with the autoconf folks to squash out as many problems as we
can and build out some kind of distro-like testing before flipping the
default.

jeff