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Re: C99 compliance for src/port/snprintf.c

Peter Eisentraut <peter.eisentraut@2ndquadrant.com>

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From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Steele <david@pgmasters.net>, pgsql-hackers@lists.postgresql.org
Date: 2018-08-16T12:54:17Z
Lists: pgsql-hackers 
On 16/08/2018 14:30, Andres Freund wrote:
> Hi,
> 
> On 2018-08-16 14:26:07 +0200, Peter Eisentraut wrote:
>> On 16/08/2018 13:18, Andres Freund wrote:
>>>   checking for ccache gcc option to accept ISO C99... unsupported
>>>
>>>   I suspect that's because of the '-ansi' flag in CFLAGS, not because
>>>   the compiler is incapable of actually supporting C99.
>>
>> -ansi is equivalent to -std=c90.  If we make the switch, the build farm
>> configuration should just probably replace -ansi with -std=c99.
> 
> Right. I just hadn't checked the addition of -std=c99 doesn't override
> the -ansi. Presumably just an ordering thing.

The mistake is putting -ansi or similar options into CFLAGS.  You need
to put them into CC.

The Autoconf test for C99 correctly puts the candidate options into CC,
but then if the test compilation invocation is something like "$CC
$CFLAGS -c conftest.c", the -ansi cancels out the earlier -std=c99 or
whatever.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Remove test for VA_ARGS, implied by C99.

  2. Introduce minimal C99 usage to verify compiler support.

  3. Require C99 (and thus MSCV 2013 upwards).

  4. Require a C99-compliant snprintf(), and remove related workarounds.

  5. Try to enable C99 in configure, but do not rely on it (yet).

  6. Make snprintf.c follow the C99 standard for snprintf's result value.

  7. Clean up assorted misuses of snprintf()'s result value.