Avoid concurrent calls to bindtextdomain().

tglsfdc · tglsfdc · commit 9fb1396a96bd · 2024-02-09T11:21:08.000-05:00
We previously supposed that it was okay for different threads to call bindtextdomain() concurrently (cf. commit 1f655fd). It now emerges that there's at least one gettext implementation in which that triggers an abort() crash, so let's stop doing that. Add mutexes guarding libpq's and ecpglib's calls, which are the only ones that need worry about multithreaded callers. Note: in libpq, we could perhaps have piggybacked on default_threadlock() to avoid defining a new mutex variable. I judge that not terribly safe though, since libpq_gettext could be called from code that is holding the default mutex. If that were the first such call in the process, it'd fail. An extra mutex is cheap insurance against unforeseen interactions. Per bug #18312 from Christian Maurer. Back-patch to all supported versions. Discussion: https://postgr.es/m/18312-bbbabc8113592b78@postgresql.org Discussion: https://postgr.es/m/264860.1707163416@sss.pgh.pa.us
diff --git a/src/interfaces/ecpg/ecpglib/misc.c b/src/interfaces/ecpg/ecpglib/misc.c
@@ -518,13 +518,14 @@ char *
 ecpg_gettext(const char *msgid)
 {
 	/*
-	 * If multiple threads come through here at about the same time, it's okay
-	 * for more than one of them to call bindtextdomain().  But it's not okay
-	 * for any of them to reach dgettext() before bindtextdomain() is
-	 * complete, so don't set the flag till that's done.  Use "volatile" just
-	 * to be sure the compiler doesn't try to get cute.
+	 * At least on Windows, there are gettext implementations that fail if
+	 * multiple threads call bindtextdomain() concurrently.  Use a mutex and
+	 * flag variable to ensure that we call it just once per process.  It is
+	 * not known that similar bugs exist on non-Windows platforms, but we
+	 * might as well do it the same way everywhere.
 	 */
 	static volatile bool already_bound = false;
+	static pthread_mutex_t binddomain_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 	if (!already_bound)
 	{
@@ -534,14 +535,26 @@ ecpg_gettext(const char *msgid)
 #else
 		int			save_errno = errno;
 #endif
-		const char *ldir;
-
-		/* No relocatable lookup here because the binary could be anywhere */
-		ldir = getenv("PGLOCALEDIR");
-		if (!ldir)
-			ldir = LOCALEDIR;
-		bindtextdomain(PG_TEXTDOMAIN("ecpglib"), ldir);
-		already_bound = true;
+
+		(void) pthread_mutex_lock(&binddomain_mutex);
+
+		if (!already_bound)
+		{
+			const char *ldir;
+
+			/*
+			 * No relocatable lookup here because the calling executable could
+			 * be anywhere
+			 */
+			ldir = getenv("PGLOCALEDIR");
+			if (!ldir)
+				ldir = LOCALEDIR;
+			bindtextdomain(PG_TEXTDOMAIN("ecpglib"), ldir);
+			already_bound = true;
+		}
+
+		(void) pthread_mutex_unlock(&binddomain_mutex);
+
 #ifdef WIN32
 		SetLastError(save_errno);
 #else
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
@@ -1274,13 +1274,14 @@ static void
 libpq_binddomain()
 {
 	/*
-	 * If multiple threads come through here at about the same time, it's okay
-	 * for more than one of them to call bindtextdomain().  But it's not okay
-	 * for any of them to return to caller before bindtextdomain() is
-	 * complete, so don't set the flag till that's done.  Use "volatile" just
-	 * to be sure the compiler doesn't try to get cute.
+	 * At least on Windows, there are gettext implementations that fail if
+	 * multiple threads call bindtextdomain() concurrently.  Use a mutex and
+	 * flag variable to ensure that we call it just once per process.  It is
+	 * not known that similar bugs exist on non-Windows platforms, but we
+	 * might as well do it the same way everywhere.
 	 */
 	static volatile bool already_bound = false;
+	static pthread_mutex_t binddomain_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 	if (!already_bound)
 	{
@@ -1290,14 +1291,26 @@ libpq_binddomain()
 #else
 		int			save_errno = errno;
 #endif
-		const char *ldir;
-
-		/* No relocatable lookup here because the binary could be anywhere */
-		ldir = getenv("PGLOCALEDIR");
-		if (!ldir)
-			ldir = LOCALEDIR;
-		bindtextdomain(PG_TEXTDOMAIN("libpq"), ldir);
-		already_bound = true;
+
+		(void) pthread_mutex_lock(&binddomain_mutex);
+
+		if (!already_bound)
+		{
+			const char *ldir;
+
+			/*
+			 * No relocatable lookup here because the calling executable could
+			 * be anywhere
+			 */
+			ldir = getenv("PGLOCALEDIR");
+			if (!ldir)
+				ldir = LOCALEDIR;
+			bindtextdomain(PG_TEXTDOMAIN("libpq"), ldir);
+			already_bound = true;
+		}
+
+		(void) pthread_mutex_unlock(&binddomain_mutex);
+
 #ifdef WIN32
 		SetLastError(save_errno);
 #else
