[PATCH 1/2] perror: call strerror_r directly

[Eric Blake]

No need to make a wrapper that burns static storage when we can
just use stack storage.

* modules/perror (Files): Drop strerror-impl.h.
* lib/perror.c (perror): Use our own stack buffer, rather than
calling a wrapper that uses static storage.
* doc/posix-functions/perror.texi (perror): Document a limitation
of our replacement.

Signed-off-by: Eric Blake <address@hidden>
---

> So about the only other thing we can do is make both strerror.c and
> strerror_r.c call into a third file that implements the gnulib
> replacement strings, and thus make it so that strerror no longer
> directly depends on strerror_r.c; patches welcome.

Thoughts on this series before I push it?

 ChangeLog                       |    7 +++++++
 doc/posix-functions/perror.texi |    4 ++++
 lib/perror.c                    |   14 +++++++++++---
 modules/perror                  |    1 -
 4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 3dc7091..a66e44d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2011-05-24  Eric Blake  <address@hidden>

+       perror: call strerror_r directly
+       * modules/perror (Files): Drop strerror-impl.h.
+       * lib/perror.c (perror): Use our own stack buffer, rather than
+       calling a wrapper that uses static storage.
+       * doc/posix-functions/perror.texi (perror): Document a limitation
+       of our replacement.
+
        strerror_r: fix missing header
        * lib/strerror_r.c: Avoid compiler warning about snprintf.

diff --git a/doc/posix-functions/perror.texi b/doc/posix-functions/perror.texi
index cf6ac79..167cf39 100644
--- a/doc/posix-functions/perror.texi
+++ b/doc/posix-functions/perror.texi
@@ -24,4 +24,8 @@ perror
 POSIX requires that this function set the stream error bit (detected
 by @code{ferror}) on write failure, but not all platforms do this:
 glibc 2.13.
address@hidden
+POSIX requires that this function not alter stream orientation, but
+the gnulib replacement locks in byte orientation and fails on wide
+character streams.
 @end itemize
diff --git a/lib/perror.c b/lib/perror.c
index 29af3c5..88981d1 100644
--- a/lib/perror.c
+++ b/lib/perror.c
@@ -40,10 +40,18 @@
 void
 perror (const char *string)
 {
-  const char *errno_description = my_strerror (errno);
+  char stackbuf[256];
+  int ret;
+
+  /* Our implementation guarantees that this will be a non-empty
+     string, even if it returns EINVAL; and stackbuf should be sized
+     large enough to avoid ERANGE.  */
+  ret = strerror_r (errno, stackbuf, sizeof stackbuf);
+  if (ret == ERANGE)
+    abort ();

   if (string != NULL && *string != '\0')
-    fprintf (stderr, "%s: %s\n", string, errno_description);
+    fprintf (stderr, "%s: %s\n", string, stackbuf);
   else
-    fprintf (stderr, "%s\n", errno_description);
+    fprintf (stderr, "%s\n", stackbuf);
 }
diff --git a/modules/perror b/modules/perror
index 1ff9ec2..38e28ce 100644
--- a/modules/perror
+++ b/modules/perror
@@ -3,7 +3,6 @@ perror() function: print a message describing error code.

 Files:
 lib/perror.c
-lib/strerror-impl.h
 m4/perror.m4

 Depends-on:
-- 
1.7.4.4