From: Peter Eisentraut <peter@eisentraut.org>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: thread-safety: gmtime_r(), localtime_r()
Date: Fri, 23 Aug 2024 05:47:25 +0000
Message-ID: <E1shN8v-0013F0-5i@gemulon.postgresql.org> (raw)
thread-safety: gmtime_r(), localtime_r()
Use gmtime_r() and localtime_r() instead of gmtime() and localtime(),
for thread-safety.
There are a few affected calls in libpq and ecpg's libpgtypes, which
are probably effectively bugs, because those libraries already claim
to be thread-safe.
There is one affected call in the backend. Most of the backend
otherwise uses the custom functions pg_gmtime() and pg_localtime(),
which are implemented differently.
While we're here, change the call in the backend to gmtime*() instead
of localtime*(), since for that use time zone behavior is irrelevant,
and this side-steps any questions about when time zones are
initialized by localtime_r() vs localtime().
Portability: gmtime_r() and localtime_r() are in POSIX but are not
available on Windows. Windows has functions gmtime_s() and
localtime_s() that can fulfill the same purpose, so we add some small
wrappers around them. (Note that these *_s() functions are also
different from the *_s() functions in the bounds-checking extension of
C11. We are not using those here.)
On MinGW, you can get the POSIX-style *_r() functions by defining
_POSIX_C_SOURCE appropriately before including <time.h>. This leads
to a conflict at least in plpython because apparently _POSIX_C_SOURCE
gets defined in some header there, and then our replacement
definitions conflict with the system definitions. To avoid that sort
of thing, we now always define _POSIX_C_SOURCE on MinGW and use the
POSIX-style functions here.
Reviewed-by: Stepan Neretin <sncfmgg@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/eba1dc75-298e-4c46-8869-48ba8aad7d70@eisentraut.org
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/a2bbc58f743489784de797d81be37ea309cb0773
Modified Files
--------------
meson.build | 4 ++++
src/backend/utils/adt/pg_locale.c | 3 ++-
src/include/port/win32_port.h | 13 +++++++++++++
src/interfaces/ecpg/pgtypeslib/dt_common.c | 11 +++++++----
src/interfaces/ecpg/pgtypeslib/timestamp.c | 3 ++-
src/interfaces/libpq/fe-trace.c | 3 ++-
src/template/win32 | 3 +++
7 files changed, 33 insertions(+), 7 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: peter@eisentraut.org, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: thread-safety: gmtime_r(), localtime_r()
In-Reply-To: <E1shN8v-0013F0-5i@gemulon.postgresql.org>
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