perror: fix POSIX compliance and work with recent newlib change

* cygtls.h (strerror_r_buf): New buffer.
* errno.cc (strerror): Move guts...
(_strerror_r): ...to new function demanded by newlib.
(strerror_r): Don't clobber strerror buffer.
(_user_strerror): Drop unused declaration.
* tlsoffsets.h: Regenerate.

1 files changed, 30 insertions, 13 deletions

diff --git a/winsup/cygwin/errno.cc b/winsup/cygwin/errno.cc
index aa311b7e2..f3b925ef2 100644
--- a/winsup/cygwin/errno.cc
+++ b/winsup/cygwin/errno.cc
@@ -360,8 +360,6 @@ seterrno (const char *file, int line)
   seterrno_from_win_error (file, line, GetLastError ());
 }
 
-extern char *_user_strerror _PARAMS ((int));
-
 static char *
 strerror_worker (int errnum)
 {
@@ -373,22 +371,38 @@ strerror_worker (int errnum)
   return res;
 }
 
-/* strerror: convert from errno values to error strings.  Newlib's
-   strerror_r returns "" for unknown values, so we override it to
-   provide a nicer thread-safe result string and set errno.  */
+/* Newlib requires this override for perror and friends to avoid
+   clobbering strerror() buffer, without having to differentiate
+   between strerror_r signatures.  This function is intentionally not
+   exported, so that only newlib can use it.  */
 extern "C" char *
-strerror (int errnum)
+_strerror_r (struct _reent *, int errnum, int internal, int *errptr)
 {
   char *errstr = strerror_worker (errnum);
   if (!errstr)
     {
-      __small_sprintf (errstr = _my_tls.locals.strerror_buf, "Unknown error %d",
-                       errnum);
-      errno = _impure_ptr->_errno = EINVAL;
+      errstr = internal ? _my_tls.locals.strerror_r_buf
+        : _my_tls.locals.strerror_buf;
+      __small_sprintf (errstr, "Unknown error %d", errnum);
+      if (errptr)
+        *errptr = EINVAL;
     }
   return errstr;
 }
 
+/* strerror: convert from errno values to error strings.  Newlib's
+   strerror_r returns "" for unknown values, so we override it to
+   provide a nicer thread-safe result string and set errno.  */
+extern "C" char *
+strerror (int errnum)
+{
+  int error = 0;
+  char *result = _strerror_r (NULL, errnum, 0, &error);
+  if (error)
+    set_errno (error);
+  return result;
+}
+
 /* Newlib's <string.h> provides declarations for two strerror_r
    variants, according to preprocessor feature macros.  However, it
    returns "" instead of "Unknown error ...", so we override both
@@ -396,10 +410,13 @@ strerror (int errnum)
 extern "C" char *
 strerror_r (int errnum, char *buf, size_t n)
 {
-  char *error = strerror (errnum);
-  if (strlen (error) >= n)
-    return error;
-  return strcpy (buf, error);
+  int error = 0;
+  char *errstr = _strerror_r (NULL, errnum, 1, &error);
+  if (error)
+    set_errno (error);
+  if (strlen (errstr) >= n)
+    return errstr;
+  return strcpy (buf, errstr);
 }
 
 extern "C" int