C89isms in the test suite

[Florian Weimer]

* Joseph Myers:

>> Other tests look like they might be intended to be built in C89 mode,
>> e.g.  gcc/testsuite/gcc.c-torture/compile/386.c, although it's not
>> immediately obvious to me what they test.
>
> For tests that might be deliberately testing implicit function 
> declarations or unprototyped functions, it's probably better to use 
> explicit options that avoid errors (note that the c-torture tests already 
> use -w to disable all warnings).

That may incur future maintenance overhead because if it's possible to
re-enable implicit declarations in later language modes, we might run
into conflicts with future standardization.

>> What's the expected default behavior for GCC 14 regarding old-style
>> function definitions (function definitions which do not have a
>> prototype)?  I assume if GCC 14 defaults to C2x mode, these no longer
>> valid constructs would be rejected by default?  Based on some earlier
>
> The existing situation is that it's a warning enabled by default in C2x 
> mode.  You could of course argue for an error instead.

I plan to make the case for a change to an error in GCC 14, but would
argue against doing this in GCC 13 already.  I just got my tester going
today (I think) and found non-trivial problem in a generic Python
distutils check, and what appears to be a systemic issue in the SWIG
binding generator.  We may have to iterate through one or more (non-GCC)
upstream releases to roll out fixes.

Thanks,
Florian