Second try at fixing ecpglib thread-safety problem.

While Windows (allegedly) has _configthreadlocale() pretty far back,
it seems MinGW didn't acquire support for that till more recently.
Fortunately, we can use an autoconf probe on that toolchain,
instead of guessing whether it's there.  (Hm, I wonder whether Cygwin
will need this also.)

Per buildfarm.

Discussion: https://postgr.es/m/20190121193512.tdmcnic2yjxlufaw@alap3.anarazel.de

configure

@@ -15942,6 +15942,17 @@ fi
 
 # Win32 (really MinGW) support
 if test "$PORTNAME" = "win32"; then
+  for ac_func in _configthreadlocale
+do :
+  ac_fn_c_check_func "$LINENO" "_configthreadlocale" "ac_cv_func__configthreadlocale"
+if test "x$ac_cv_func__configthreadlocale" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE__CONFIGTHREADLOCALE 1
+_ACEOF
+
+fi
+done
+
   ac_fn_c_check_func "$LINENO" "gettimeofday" "ac_cv_func_gettimeofday"
 if test "x$ac_cv_func_gettimeofday" = xyes; then :
   $as_echo "#define HAVE_GETTIMEOFDAY 1" >>confdefs.h

configure.in

@@ -1754,6 +1754,7 @@ fi
 
 # Win32 (really MinGW) support
 if test "$PORTNAME" = "win32"; then
+  AC_CHECK_FUNCS(_configthreadlocale)
   AC_REPLACE_FUNCS(gettimeofday)
   AC_LIBOBJ(dirmod)
   AC_LIBOBJ(kill)

src/include/pg_config.h.in

@@ -757,6 +757,9 @@
 /* Define to 1 if your compiler understands __builtin_unreachable. */
 #undef HAVE__BUILTIN_UNREACHABLE
 
+/* Define to 1 if you have the `_configthreadlocale' function. */
+#undef HAVE__CONFIGTHREADLOCALE
+
 /* Define to 1 if you have __cpuid. */
 #undef HAVE__CPUID
 

src/include/pg_config.h.win32

@@ -596,6 +596,9 @@
 /* Define to 1 if your compiler understands __builtin_unreachable. */
 /* #undef HAVE__BUILTIN_UNREACHABLE */
 
+/* Define to 1 if you have the `_configthreadlocale' function. */
+#define HAVE__CONFIGTHREADLOCALE 1
+
 /* Define to 1 if you have __cpuid. */
 #define HAVE__CPUID 1
 

src/interfaces/ecpg/ecpglib/descriptor.c

@@ -495,7 +495,7 @@ ECPGget_desc(int lineno, const char *desc_name, int index,...)
 		if (stmt.clocale != (locale_t) 0)
 			stmt.oldlocale = uselocale(stmt.clocale);
 #else
-#ifdef WIN32
+#ifdef HAVE__CONFIGTHREADLOCALE
 		stmt.oldthreadlocale = _configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
 #endif
 		stmt.oldlocale = ecpg_strdup(setlocale(LC_NUMERIC, NULL), lineno);
@@ -517,7 +517,7 @@ ECPGget_desc(int lineno, const char *desc_name, int index,...)
 			setlocale(LC_NUMERIC, stmt.oldlocale);
 			ecpg_free(stmt.oldlocale);
 		}
-#ifdef WIN32
+#ifdef HAVE__CONFIGTHREADLOCALE
 		if (stmt.oldthreadlocale != -1)
 			_configthreadlocale(stmt.oldthreadlocale);
 #endif

src/interfaces/ecpg/ecpglib/ecpglib_extern.h

@@ -69,7 +69,7 @@ struct statement
 	locale_t	oldlocale;
 #else
 	char	   *oldlocale;
-#ifdef WIN32
+#ifdef HAVE__CONFIGTHREADLOCALE
 	int			oldthreadlocale;
 #endif
 #endif

src/interfaces/ecpg/ecpglib/execute.c

@@ -1778,7 +1778,7 @@ 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.  If available, use
 	 * uselocale() for this because it's thread-safe.  Windows doesn't have
-	 * that, but it does have _configthreadlocale().
+	 * that, but it usually does have _configthreadlocale().
 	 */
 #ifdef HAVE_USELOCALE
 	stmt->clocale = newlocale(LC_NUMERIC_MASK, "C", (locale_t) 0);
@@ -1794,7 +1794,7 @@ ecpg_do_prologue(int lineno, const int compat, const int force_indicator,
 		return false;
 	}
 #else
-#ifdef WIN32
+#ifdef HAVE__CONFIGTHREADLOCALE
 	stmt->oldthreadlocale = _configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
 	if (stmt->oldthreadlocale == -1)
 	{
@@ -2019,7 +2019,7 @@ ecpg_do_epilogue(struct statement *stmt)
 	if (stmt->oldlocale)
 	{
 		setlocale(LC_NUMERIC, stmt->oldlocale);
-#ifdef WIN32
+#ifdef HAVE__CONFIGTHREADLOCALE
 		_configthreadlocale(stmt->oldthreadlocale);
 #endif
 	}