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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>, Dave Page <dpage@pgadmin.org>
Cc: David Steele <david@pgmasters.net>, pgsql-hackers@lists.postgresql.org
Date: 2018-08-16T14:22:20Z
Lists: pgsql-hackers 
Hi,

On 2018-08-16 04:18:59 -0700, Andres Freund wrote:
> Besides gaur, I'm also awaiting casteroides' results. The latter
> definitely does support C99, but I'm not sure autconf pushes hard
> enough.  I think every other relevant animal has reported back.

Casteroides wasn't a problem, -D_STDC_C99= does the trick.

But enabling C99 support triggered a somewhat weird failure on
protosciurus (also solaris, but gcc)
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=protosciurus&dt=2018-08-16%2013%3A37%3A46

It detects C99 support successfully via -std=gnu99 but then fails
somewhere during build with:

gcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -Wno-unused-command-line-argument -g -I/usr/local/include -m64 -I../../../../src/include    -c -o gistutil.o gistutil.c
In file included from gistutil.c:24:
../../../../src/include/utils/float.h: In function `get_float4_infinity':
../../../../src/include/utils/float.h:71: error: `__builtin_infinity' undeclared (first use in this function)
../../../../src/include/utils/float.h:71: error: (Each undeclared identifier is reported only once
../../../../src/include/utils/float.h:71: error: for each function it appears in.)
../../../../src/include/utils/float.h: In function `get_float8_infinity':
../../../../src/include/utils/float.h:91: error: `__builtin_infinity' undeclared (first use in this function)
../../../../src/include/utils/float.h: In function `get_float4_nan':
../../../../src/include/utils/float.h:108: error: pointer value used where a floating point value was expected
../../../../src/include/utils/float.h: In function `get_float8_nan':
../../../../src/include/utils/float.h:121: error: pointer value used where a floating point value was expected
../../../../src/include/utils/float.h: In function `check_float4_val':
../../../../src/include/utils/float.h:136: warning: implicit declaration of function `__builtin_isinf'
../../../../src/include/utils/float.h: In function `float4_eq':
../../../../src/include/utils/float.h:283: warning: implicit declaration of function `__builtin_isnan'

While I'd personally have no problem kicking gcc 3.4 to the curb, I'm
still confused what causes this error mode.  Kinda looks like
out-of-sync headers with gcc or something.

Greetings,

Andres Freund

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.