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: Alexander Kuzmenkov <a.kuzmenkov@postgrespro.ru>, pgsql-hackers@lists.postgresql.org
Date: 2018-10-03T17:51:38Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2018-10-03 13:18:35 -0400, Tom Lane wrote:
>> Having said that, maybe there's a case for changing the type spec
>> in only the va_arg() call, and leaving snprintf's related local
>> variables as int64.  (Is that what you actually meant?)  Then,
>> if long long really is different from int64, at least we have
>> predictable truncation behavior after fetching the value, rather
>> than undefined behavior while fetching it.

> Hm. I guess that'd be a bit better, but I'm not sure it's worth it. How
> about we simply add a static assert that long long isn't bigger than
> int64?

WFM, I'll make it happen.

			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().