# HG changeset patch
# User Eric Blake <eblake@redhat.com>
# Date 1308672055 21600
# Node ID 8254c62701307f939a83b9b7b0ced2054ea99353
# Parent  a3ba680ad389a46d5655913b1f2cd949dc95ca6e
strerror_r: fix OpenBSD behavior on out-of-range

On OpenBSD, strerror_r(1000,buf,19) gives "Unknown error: " rather
than "Unknown error: 100" while failing with ERANGE.  Admittedly,
this behavior is nice, since a truncated integer is misleading,
but all other platforms use maximal strings on ERANGE and we are
already replacing strerror_r for other reasons, so it is easier
to work around this behavior than to adjust the testsuite (how
do you quickly decide if the only reason that the ERANGE string
was shorter than maximal was because the implementation avoided
truncating an integer?).

This patch intentionally avoids dragging in the strnlen module.

* lib/strerror_r.c (strerror_r): Always use maximal string.
* doc/posix-functions/strerror_r.texi (strerror_r): Document it.

Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2011-06-21  Eric Blake  <eblake@redhat.com>
 
+	strerror_r: fix OpenBSD behavior on out-of-range
+	* lib/strerror_r.c (strerror_r): Always use maximal string.
+	* doc/posix-functions/strerror_r.texi (strerror_r): Document it.
+
 	strerror_r: fix OpenBSD behavior on 0
 	* lib/strerror-override.c (strerror_override): Also override 0
 	when needed.
diff --git a/doc/posix-functions/strerror_r.texi b/doc/posix-functions/strerror_r.texi
--- a/doc/posix-functions/strerror_r.texi
+++ b/doc/posix-functions/strerror_r.texi
@@ -64,6 +64,11 @@
 function fails to leave a NUL-terminated string in the buffer on some
 platforms:
 glibc 2.13, FreeBSD 8.2, Solaris 10.
+@item
+When the value is out of range but the buffer is too small, this
+function does not always return the longest possible string on some
+platforms:
+OpenBSD 4.7.
 @end itemize
 
 Portability problems not fixed by Gnulib:
diff --git a/lib/strerror_r.c b/lib/strerror_r.c
--- a/lib/strerror_r.c
+++ b/lib/strerror_r.c
@@ -175,17 +175,11 @@
         ret = strerror_r (errnum, buf, buflen);
     }
 # else
-    /* Solaris 10 does not populate buf on ERANGE.  */
     ret = strerror_r (errnum, buf, buflen);
-    if (ret == ERANGE && !*buf)
-      {
-        char stackbuf[STACKBUF_LEN];
 
-        if (strerror_r (errnum, stackbuf, sizeof stackbuf) == ERANGE)
-          /* STACKBUF_LEN should have been large enough.  */
-          abort ();
-        safe_copy (buf, buflen, stackbuf);
-      }
+    /* Some old implementations may return (-1, EINVAL) instead of EINVAL.  */
+    if (ret < 0)
+      ret = errno;
 # endif
 
 # ifdef _AIX
@@ -203,11 +197,23 @@
         if (buflen <= len)
           ret = ERANGE;
       }
-# endif
+# else
+    /* Solaris 10 does not populate buf on ERANGE.  OpenBSD 4.7
+       truncates early on ERANGE rather than return a partial integer.
+       We prefer the maximal string.  We set buf[0] earlier, and we
+       know of no implementation that modifies buf to be an
+       unterminated string, so this strlen should be portable in
+       practice (rather than pulling in a safer strnlen).  */
+    if (ret == ERANGE && strlen (buf) < buflen - 1)
+      {
+        char stackbuf[STACKBUF_LEN];
 
-    /* Some old implementations may return (-1, EINVAL) instead of EINVAL.  */
-    if (ret < 0)
-      ret = errno;
+        /* STACKBUF_LEN should have been large enough.  */
+        if (strerror_r (errnum, stackbuf, sizeof stackbuf) == ERANGE)
+          abort ();
+        safe_copy (buf, buflen, stackbuf);
+      }
+# endif
 
 #else /* USE_SYSTEM_STRERROR */