Avoid thread-safety problem in ecpglib.

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

1 files changed, 30 insertions, 7 deletions

diff --git a/src/interfaces/ecpg/ecpglib/descriptor.c b/src/interfaces/ecpg/ecpglib/descriptor.c
index 186f92cc3ed..71cef151724 100644
--- a/src/interfaces/ecpg/ecpglib/descriptor.c
+++ b/src/interfaces/ecpg/ecpglib/descriptor.c
@@ -483,22 +483,45 @@ ECPGget_desc(int lineno, const char *desc_name, int index,...)
 	if (data_var.type != ECPGt_EORT)
 	{
 		struct statement stmt;
-		char	   *oldlocale;
+
+		memset(&stmt, 0, sizeof stmt);
+		stmt.lineno = lineno;
 
 		/* Make sure we do NOT honor the locale for numeric input */
 		/* since the database gives the standard decimal point */
-		oldlocale = ecpg_strdup(setlocale(LC_NUMERIC, NULL), lineno);
+		/* (see comments in execute.c) */
+#ifdef HAVE_USELOCALE
+		stmt.clocale = newlocale(LC_NUMERIC_MASK, "C", (locale_t) 0);
+		if (stmt.clocale != (locale_t) 0)
+			stmt.oldlocale = uselocale(stmt.clocale);
+#else
+#ifdef WIN32
+		stmt.oldthreadlocale = _configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
+#endif
+		stmt.oldlocale = ecpg_strdup(setlocale(LC_NUMERIC, NULL), lineno);
 		setlocale(LC_NUMERIC, "C");
-
-		memset(&stmt, 0, sizeof stmt);
-		stmt.lineno = lineno;
+#endif
 
 		/* desperate try to guess something sensible */
 		stmt.connection = ecpg_get_connection(NULL);
 		ecpg_store_result(ECPGresult, index, &stmt, &data_var);
 
-		setlocale(LC_NUMERIC, oldlocale);
-		ecpg_free(oldlocale);
+#ifdef HAVE_USELOCALE
+		if (stmt.oldlocale != (locale_t) 0)
+			uselocale(stmt.oldlocale);
+		if (stmt.clocale)
+			freelocale(stmt.clocale);
+#else
+		if (stmt.oldlocale)
+		{
+			setlocale(LC_NUMERIC, stmt.oldlocale);
+			ecpg_free(stmt.oldlocale);
+		}
+#ifdef WIN32
+		if (stmt.oldthreadlocale != -1)
+			_configthreadlocale(stmt.oldthreadlocale);
+#endif
+#endif
 	}
 	else if (data_var.ind_type != ECPGt_NO_INDICATOR && data_var.ind_pointer != NULL)