Local type inference with auto is in C2X

[David Brown]

On 03/11/2022 16:19, Michael Matz via Gcc wrote:
> Hello,
> 
> On Thu, 3 Nov 2022, Florian Weimer via Gcc wrote:
> 
>> will not have propagated widely once GCC 13 releases, so rejecting
>> implicit ints in GCC 13 might be too early.  GCC 14 might want to switch
>> to C23/C24 mode by default, activating auto support, if the standard
>> comes out in 2023 (which apparently is the plan).
>>
>> Then we would go from
>> warning to changed semantics in a single release.
>>
>> Comments?
> 
> I would argue that changing the default C mode to c23 in the year that
> comes out (or even a year later) is too aggressive and early.  Existing
> sources are often compiled with defaults, and hence would change
> semantics, which seems unattractive.  New code can instead easily use
> -std=c23 for a time.
> 
> E.g. c99/gnu99 (a largish deviation from gnu90) was never default and
> gnu11 was made default only in 2014.
> 

That's true - and the software world still has not recovered from the 
endless mass of drivel that gcc (and other compilers) accepted in lieu 
of decent C as a result of not changing to C99 as the standard.

Good C programmers put the standards flag explicitly in their makefile 
(or other build system).  Bad ones use whatever the compiler gives them 
by default and believe "the compiler accepted it, it must be good code".

My vote would be to make "-std=c17 -Wall -Wextra -Wpedantic -Werror -O2" 
the default flags.  Force those who don't really know what they are 
doing, to learn - it's not /that/ hard, and the effort pays off quickly. 
  (Or they can give up and move to Python.)  Those who understand how to 
use their tools can happily change the standards and warnings to suit 
their needs.

And the person who first decided "implicit declaration of function" 
should merely be a /warning/ should be sentenced to 10 years Cobol 
programming.

It's probably a good thing that it is not I who decides the default 
flags for gcc !