string: Implement strerror in terms of strerror_l

If the thread is terminated then __libc_thread_freeres will free the
storage via __glibc_tls_internal_free.

It is only within the calling thread that this matters.  It makes
strerror MT-safe.

Checked on x86-64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
and s390x-linux-gnu.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

2 files changed, 12 insertions, 25 deletions

diff --git a/string/strerror.c b/string/strerror.c
index 283ab70..35c7490 100644
--- a/string/strerror.c
+++ b/string/strerror.c
@@ -15,29 +15,11 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <libintl.h>
-#include <stdio.h>
 #include <string.h>
-#include <errno.h>
-
-/* Return a string describing the errno code in ERRNUM.
-   The storage is good only until the next call to strerror.
-   Writing to the storage causes undefined behavior.  */
-libc_freeres_ptr (static char *buf);
+#include <locale/localeinfo.h>
 
 char *
 strerror (int errnum)
 {
-  char *ret = __strerror_r (errnum, NULL, 0);
-  int saved_errno;
-
-  if (__glibc_likely (ret != NULL))
-    return ret;
-  saved_errno = errno;
-  if (buf == NULL)
-    buf = malloc (1024);
-  __set_errno (saved_errno);
-  if (buf == NULL)
-    return _("Unknown error");
-  return __strerror_r (errnum, buf, 1024);
+  return __strerror_l (errnum, __libc_tsd_get (locale_t, LOCALE));
 }
diff --git a/string/strerror_l.c b/string/strerror_l.c
index 309f42e..017bd14 100644
--- a/string/strerror_l.c
+++ b/string/strerror_l.c
@@ -20,8 +20,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/param.h>
-#include <libc-symbols.h>
+#include <errno.h>
 
 static __thread char *last_value;
 
@@ -38,8 +37,9 @@ translate (const char *str, locale_t loc)
 
 /* Return a string describing the errno code in ERRNUM.  */
 char *
-strerror_l (int errnum, locale_t loc)
+__strerror_l (int errnum, locale_t loc)
 {
+  int saved_errno = errno;
   char *err = (char *) __get_errlist (errnum);
   if (__glibc_unlikely (err == NULL))
     {
@@ -48,11 +48,16 @@ strerror_l (int errnum, locale_t loc)
 		      translate ("Unknown error ", loc), errnum) == -1)
 	last_value = NULL;
 
-      return last_value;
+      err = last_value;
     }
+  else
+    err = (char *) translate (err, loc);
 
-  return (char *) translate (err, loc);
+  __set_errno (saved_errno);
+  return err;
 }
+weak_alias (__strerror_l, strerror_l)
+libc_hidden_def (__strerror_l)
 
 void
 __strerror_thread_freeres (void)