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

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Since our substitute snprintf now returns a C99-compliant result,
there's no need anymore to have complicated code to cope with pre-C99
behavior.  We can just make configure substitute snprintf.c if it finds
that the system snprintf() is pre-C99.  (Note: I do not believe that
there are any platforms where this test will trigger that weren't
already being rejected due to our other C99-ish feature requirements for
snprintf.  But let's add the check for paranoia's sake.)  Then, simplify
the call sites that had logic to cope with the pre-C99 definition.

I also dropped some stuff that was being paranoid about the possibility
of snprintf overrunning the given buffer.  The only reports we've ever
heard of that being a problem were for Solaris 7, which is long dead,
and we've sure not heard any reports of these assertions triggering in
a long time.  So let's drop that complexity too.

Likewise, drop some code that wasn't trusting snprintf to set errno
when it returns -1.  That would be not-per-spec, and again there's
no real reason to believe it is a live issue, especially not for
snprintfs that pass all of configure's feature checks.

Discussion: https://postgr.es/m/17245.1534289329@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2018-08-16 13:01:09 -04:00
parent 1eb9221585
commit e1d19c902e
6 changed files with 125 additions and 123 deletions
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23
src/backend/utils/misc/guc.c
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@ -9441,26 +9441,19 @@ do_serialize(char **destptr, Size *maxbytes, const char *fmt,...)
if (*maxbytes <= 0)
elog(ERROR, "not enough space to serialize GUC state");
errno = 0;
va_start(vargs, fmt);
n = vsnprintf(*destptr, *maxbytes, fmt, vargs);
va_end(vargs);
/*
* Cater to portability hazards in the vsnprintf() return value just like
* appendPQExpBufferVA() does. Note that this requires an extra byte of
* slack at the end of the buffer. Since serialize_variable() ends with a
* do_serialize_binary() rather than a do_serialize(), we'll always have
* that slack; estimate_variable_size() need not add a byte for it.
*/
if (n < 0 || n >= *maxbytes - 1)
if (n < 0)
{
if (n < 0 && errno != 0 && errno != ENOMEM)
/* Shouldn't happen. Better show errno description. */
elog(ERROR, "vsnprintf failed: %m");
else
elog(ERROR, "not enough space to serialize GUC state");
/* Shouldn't happen. Better show errno description. */
elog(ERROR, "vsnprintf failed: %m");
}
if (n >= *maxbytes)
{
/* This shouldn't happen either, really. */
elog(ERROR, "not enough space to serialize GUC state");
}
/* Shift the destptr ahead of the null terminator */