Horton

Re: Performance improvements for src/port/snprintf.c

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@lists.postgresql.org, Thomas Munro <thomas.munro@enterprisedb.com>, Andrew Gierth <andrew@tao11.riddles.org.uk>, Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>
Date: 2018-10-03T18:48:59Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2018-10-03 14:01:35 -0400, Tom Lane wrote:
>> BTW, so far as I can tell on F28, strfromd isn't exposed without
>> "-D__STDC_WANT_IEC_60559_BFP_EXT__", which seems fairly scary;
>> what else does that affect?

> So I don't think anything's needed to enable that in pg, given that we
> define _GNU_SOURCE

Ah, OK.  I thought my test case had _GNU_SOURCE defined already,
but it didn't.  You might want to do something like what I stuck
in for strchrnul, though:

/*
 * glibc's <string.h> declares strchrnul only if _GNU_SOURCE is defined.
 * While we typically use that on glibc platforms, configure will set
 * HAVE_STRCHRNUL whether it's used or not.  Fill in the missing declaration
 * so that this file will compile cleanly with or without _GNU_SOURCE.
 */
#ifndef _GNU_SOURCE
extern char *strchrnul(const char *s, int c);
#endif


			regards, tom lane

Commits

  1. Improve snprintf.c's handling of NaN, Infinity, and minus zero.

  2. Rationalize snprintf.c's handling of "ll" formats.

  3. Provide fast path in snprintf.c for conversion specs that are just "%s".

  4. Make assorted performance improvements in snprintf.c.

  5. Set snprintf.c's maximum number of NL arguments to be 31.

  6. Always use our own versions of *printf().