hard-locale: Make multithread-safe.

* lib/hard-locale.h (hard_locale): Move documentation to here.
* lib/hard-locale.c: Don't include <stdlib.h>.
(GLIBC_VERSION): Remove macro.
(hard_locale): Assume that all systems name the "C" and "POSIX" locales
"C" or "POSIX". Invoke setlocale_null instead of setlocale.
* modules/hard-locale (Depends-on): Remove strdup. Add setlocale-null.
(configure.ac): Require gl_FUNC_SETLOCALE_NULL. Set LIB_HARD_LOCALE.
(Link): New section.
* modules/hard-locale-tests (Makefile.am): Link test-hard-locale against
$(LIB_HARD_LOCALE).

5 files changed, 30 insertions, 43 deletions

diff --git a/ChangeLog b/ChangeLog
index 2f41e5e8a7..e2c33fb163 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,19 @@
 2019-12-18  Bruno Haible  <bruno@clisp.org>
 
+	hard-locale: Make multithread-safe.
+	* lib/hard-locale.h (hard_locale): Move documentation to here.
+	* lib/hard-locale.c: Don't include <stdlib.h>.
+	(GLIBC_VERSION): Remove macro.
+	(hard_locale): Assume that all systems name the "C" and "POSIX" locales
+	"C" or "POSIX". Invoke setlocale_null instead of setlocale.
+	* modules/hard-locale (Depends-on): Remove strdup. Add setlocale-null.
+	(configure.ac): Require gl_FUNC_SETLOCALE_NULL. Set LIB_HARD_LOCALE.
+	(Link): New section.
+	* modules/hard-locale-tests (Makefile.am): Link test-hard-locale against
+	$(LIB_HARD_LOCALE).
+
+2019-12-18  Bruno Haible  <bruno@clisp.org>
+
 	hard-locale: Avoid test failure on Haiku.
 	* tests/test-hard-locale.c (test_one): Treat Haiku like recent OpenBSD.
 
diff --git a/lib/hard-locale.c b/lib/hard-locale.c
index dcfcad62ee..4a2adabb7e 100644
--- a/lib/hard-locale.c
+++ b/lib/hard-locale.c
@@ -21,52 +21,15 @@
 #include "hard-locale.h"
 
 #include <locale.h>
-#include <stdlib.h>
 #include <string.h>
 
-#ifdef __GLIBC__
-# define GLIBC_VERSION __GLIBC__
-#elif defined __UCLIBC__
-# define GLIBC_VERSION 2
-#else
-# define GLIBC_VERSION 0
-#endif
-
-/* Return true if the current CATEGORY locale is hard, i.e. if you
-   can't get away with assuming traditional C or POSIX behavior.  */
 bool
 hard_locale (int category)
 {
-  bool hard = true;
-  char const *p = setlocale (category, NULL);
-
-  if (p)
-    {
-      if (2 <= GLIBC_VERSION)
-        {
-          if (strcmp (p, "C") == 0 || strcmp (p, "POSIX") == 0)
-            hard = false;
-        }
-      else
-        {
-          char *locale = strdup (p);
-          if (locale)
-            {
-              /* Temporarily set the locale to the "C" and "POSIX" locales
-                 to find their names, so that we can determine whether one
-                 or the other is the caller's locale.  */
-              if (((p = setlocale (category, "C"))
-                   && strcmp (p, locale) == 0)
-                  || ((p = setlocale (category, "POSIX"))
-                      && strcmp (p, locale) == 0))
-                hard = false;
+  char locale[SETLOCALE_NULL_MAX];
 
-              /* Restore the caller's locale.  */
-              setlocale (category, locale);
-              free (locale);
-            }
-        }
-    }
+  if (setlocale_null (category, locale, sizeof (locale)))
+    return false;
 
-  return hard;
+  return !(strcmp (locale, "C") == 0 || strcmp (locale, "POSIX") == 0);
 }
diff --git a/lib/hard-locale.h b/lib/hard-locale.h
index 8f1da96e2f..160674ba7a 100644
--- a/lib/hard-locale.h
+++ b/lib/hard-locale.h
@@ -20,6 +20,9 @@
 
 # include <stdbool.h>
 
-bool hard_locale (int);
+/* Return true if the specified CATEGORY of the current locale is hard, i.e.
+   different from the C or POSIX locale that has a fixed behavior.
+   CATEGORY must be one of the LC_* values, but not LC_ALL.  */
+extern bool hard_locale (int category);
 
 #endif /* HARD_LOCALE_H_ */
diff --git a/modules/hard-locale b/modules/hard-locale
index d4463b74bd..df07d4a6ed 100644
--- a/modules/hard-locale
+++ b/modules/hard-locale
@@ -7,9 +7,12 @@ lib/hard-locale.c
 
 Depends-on:
 stdbool
-strdup
+setlocale-null
 
 configure.ac:
+AC_REQUIRE([gl_FUNC_SETLOCALE_NULL])
+LIB_HARD_LOCALE="$LIB_SETLOCALE_NULL"
+AC_SUBST([LIB_HARD_LOCALE])
 
 Makefile.am:
 lib_SOURCES += hard-locale.c
@@ -17,6 +20,9 @@ lib_SOURCES += hard-locale.c
 Include:
 "hard-locale.h"
 
+Link:
+$(LIB_HARD_LOCALE)
+
 License:
 LGPLv2+
 
diff --git a/modules/hard-locale-tests b/modules/hard-locale-tests
index cdc084eba4..a501781d8d 100644
--- a/modules/hard-locale-tests
+++ b/modules/hard-locale-tests
@@ -16,3 +16,4 @@ Makefile.am:
 TESTS += test-hard-locale
 check_PROGRAMS += test-hard-locale
 noinst_PROGRAMS += locale
+test_hard_locale_LDADD = $(LDADD) @LIB_HARD_LOCALE@