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

[Joseph Myers]

On Fri, 2 Nov 2018, Martin Sebor wrote:

> I have reworked the patch to resolve any lingering concerns about
> warnings in configure tests.  The attached revision only warns
> with -Wextra and only for incompatible declarations of built-ins
> that take arguments.  For void built-ins like abort() it only
> warns with -Wpedantic (this required adjustments to several
> tests that are being compiled with -pedantic-errors).

I don't think this use of -Wpedantic is appropriate.  -Wpedantic is not a 
catch-all for warnings we don't want to enable with some other option; 
it's specifically for programs doing something that is disallowed by ISO C 
(such warnings may or may not also be enabled by other relevant options).

Since this declaration is not disallowed by ISO C, -Wpedantic should not 
result in a warning for it.

(I do consider declarations with () for built-in functions without 
arguments to be more dubious than for user-defined functions without 
arguments, simply because good practice would be to include the standard 
header to get declarations of those functions, whereas for user-defined 
functions the code might simply be using C++ style for declaring functions 
without arguments.)

-- 
Joseph S. Myers
joseph@codesourcery.com