fix perror POSIX compliance

fix perror POSIX compliance

[Eric Blake]

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This depends on the newlib patch:
http://sourceware.org/ml/newlib/2011/msg00215.html

In fact, if that patch goes in, then this one is required to avoid a
link failure; this one can probably go in first but makes no difference
to perror without the newlib patch.

 winsup/cygwin/ChangeLog    |    6 +++
 winsup/cygwin/cygtls.h     |    1 +
 winsup/cygwin/errno.cc     |   43 ++++++++++++++++-------
 winsup/cygwin/tlsoffsets.h |   82
++++++++++++++++++++++----------------------
 4 files changed, 78 insertions(+), 54 deletions(-)

2011-05-23  Eric Blake  <eblake@redhat.com>

	* 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.

diff --git a/winsup/cygwin/cygtls.h b/winsup/cygwin/cygtls.h
index 6359e7c..a1642b1 100644
--- a/winsup/cygwin/cygtls.h
+++ b/winsup/cygwin/cygtls.h
@@ -110,6 +110,7 @@ struct _local_storage

   /* strerror errno.cc */
   char strerror_buf[sizeof ("Unknown error -2147483648")];
+  char strerror_r_buf[sizeof ("Unknown error -2147483648")];

   /* times.cc */
   char timezone_buf[20];
diff --git a/winsup/cygwin/errno.cc b/winsup/cygwin/errno.cc
index aa311b7..f3b925e 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
diff --git a/winsup/cygwin/tlsoffsets.h b/winsup/cygwin/tlsoffsets.h
index 4e459df..3ef7963 100644
--- a/winsup/cygwin/tlsoffsets.h
+++ b/winsup/cygwin/tlsoffsets.h
@@ -1,6 +1,6 @@
 //;# autogenerated:  Do not edit.

-//; $tls::sizeof__cygtls = 3984;
+//; $tls::sizeof__cygtls = 4012;
... // rest of generated file patch elided

-- 
Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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Re: fix perror POSIX compliance

[Corinna Vinschen]

On May 23 17:28, Eric Blake wrote:
> This depends on the newlib patch:
> http://sourceware.org/ml/newlib/2011/msg00215.html
> 
> In fact, if that patch goes in, then this one is required to avoid a
> link failure; this one can probably go in first but makes no difference
> to perror without the newlib patch.

You can apply this together with the newlib patch.  But please
make sure that you also tested the newlib-only implementation.


Thanks,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

Re: fix perror POSIX compliance

[Eric Blake]

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On 05/24/2011 04:09 AM, Corinna Vinschen wrote:
> On May 23 17:28, Eric Blake wrote:
>> This depends on the newlib patch:
>> http://sourceware.org/ml/newlib/2011/msg00215.html
>>
>> In fact, if that patch goes in, then this one is required to avoid a
>> link failure; this one can probably go in first but makes no difference
>> to perror without the newlib patch.
> 
> You can apply this together with the newlib patch.  But please
> make sure that you also tested the newlib-only implementation.

Yep, tested both, and now pushed.

-- 
Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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