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Avoid thread-safety problem in ecpglib.

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ecpglib attempts to force the LC_NUMERIC locale to "C" while reading
server output, to avoid problems with strtod() and related functions.
Historically it's just issued setlocale() calls to do that, but that
has major problems if we're in a threaded application.  setlocale()
itself is not required by POSIX to be thread-safe (and indeed is not,
on recent OpenBSD).  Moreover, its effects are process-wide, so that
we could cause unexpected results in other threads, or another thread
could change our setting.

On platforms having uselocale(), which is required by POSIX:2008,
we can avoid these problems by using uselocale() instead.  Windows
goes its own way as usual, but we can make it safe by using
_configthreadlocale().  Platforms having neither continue to use the
old code, but that should be pretty much nobody among current systems.

This should get back-patched, but let's see what the buildfarm
thinks of it first.

Michael Meskes and Tom Lane; thanks also to Takayuki Tsunakawa.

Discussion: https://postgr.es/m/31420.1547783697@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2019-01-21 12:07:02 -05:00
parent f4593bd2ff
commit 8eb4a9312c
7 changed files with 91 additions and 10 deletions
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42
src/interfaces/ecpg/ecpglib/execute.c
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@ -102,7 +102,12 @@ free_statement(struct statement *stmt)
free_variable(stmt->outlist);
ecpg_free(stmt->command);
ecpg_free(stmt->name);
#ifdef HAVE_USELOCALE
if (stmt->clocale)
freelocale(stmt->clocale);
#else
ecpg_free(stmt->oldlocale);
#endif
ecpg_free(stmt);
}
@ -1771,8 +1776,32 @@ ecpg_do_prologue(int lineno, const int compat, const int force_indicator,
/*
* Make sure we do NOT honor the locale for numeric input/output since the
* database wants the standard decimal point
* database wants the standard decimal point. If available, use
* uselocale() for this because it's thread-safe. Windows doesn't have
* that, but it does have _configthreadlocale().
*/
#ifdef HAVE_USELOCALE
stmt->clocale = newlocale(LC_NUMERIC_MASK, "C", (locale_t) 0);
if (stmt->clocale == (locale_t) 0)
{
ecpg_do_epilogue(stmt);
return false;
}
stmt->oldlocale = uselocale(stmt->clocale);
if (stmt->oldlocale == (locale_t) 0)
{
ecpg_do_epilogue(stmt);
return false;
}
#else
#ifdef WIN32
stmt->oldthreadlocale = _configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
if (stmt->oldthreadlocale == -1)
{
ecpg_do_epilogue(stmt);
return false;
}
#endif
stmt->oldlocale = ecpg_strdup(setlocale(LC_NUMERIC, NULL), lineno);
if (stmt->oldlocale == NULL)
{
@ -1780,6 +1809,7 @@ ecpg_do_prologue(int lineno, const int compat, const int force_indicator,
return false;
}
setlocale(LC_NUMERIC, "C");
#endif
#ifdef ENABLE_THREAD_SAFETY
ecpg_pthreads_init();
@ -1982,8 +2012,18 @@ ecpg_do_epilogue(struct statement *stmt)
if (stmt == NULL)
return;
#ifdef HAVE_USELOCALE
if (stmt->oldlocale != (locale_t) 0)
uselocale(stmt->oldlocale);
#else
if (stmt->oldlocale)
{
setlocale(LC_NUMERIC, stmt->oldlocale);
#ifdef WIN32
_configthreadlocale(stmt->oldthreadlocale);
#endif
}
#endif
free_statement(stmt);
}