[commit] Re: [PATCH] Avoid potencially-stale errno usage

[Pedro Alves <palves at redhat dot com>]

On 04/08/2013 07:34 PM, Jan Kratochvil wrote:
> On Mon, 08 Apr 2013 19:57:22 +0200, Pedro Alves wrote:
>> @@ -7048,14 +7065,11 @@ readchar (int timeout)
>>    switch ((enum serial_rc) ch)
>>      {
>>      case SERIAL_EOF:
>> -      remote_unpush_target ();
>> -      throw_error (TARGET_CLOSE_ERROR, _("Remote connection closed"));
>> +      unpush_and_perror (_("Remote connection closed"));
> 
> I do not see why you have changed this part.  I have checked SERIAL_EOF is
> returned in cases where errno is not set (errno is unchanged).

Gah.  Is "patch sent in a hurry; wife and kid waiting in car" a good excuse?  :-P

> Otherwise it looks OK to me.

Thanks.  Committed.

---------------
Avoid potencially-stale errno usage.

The current throw_perror_with_name/TARGET_CLOSE_ERROR calls assume
errno is still set to the right error, although remote_unpush_target
is called in between, which may well change errno.

Tested on x86_64 Fedora 17 w/ gdbserver.

gdb/
2013-04-09  Pedro Alves  <palves@redhat.com>

	* remote.c (unpush_and_perror): New function.
	(readchar, remote_serial_write): Use it.
---
 gdb/remote.c |   29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index 740324b..de075c8 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -7033,6 +7033,23 @@ remote_files_info (struct target_ops *ignore)
 /* Stuff for dealing with the packets which are part of this protocol.
    See comment at top of file for details.  */
 
+/* Close/unpush the remote target, and throw a TARGET_CLOSE_ERROR
+   error to higher layers.  Called when a serial error is detected.
+   The exception message is STRING, followed by a colon and a blank,
+   then the system error message for errno at function entry.  */
+
+static void
+unpush_and_perror (const char *string)
+{
+  char *errstr;
+
+  errstr = xstrprintf ("%s: %s", string, safe_strerror (errno));
+  make_cleanup (xfree, errstr);
+
+  remote_unpush_target ();
+  throw_error (TARGET_CLOSE_ERROR, "%s", errstr);
+}
+
 /* Read a single character from the remote end.  */
 
 static int
@@ -7052,10 +7069,8 @@ readchar (int timeout)
       throw_error (TARGET_CLOSE_ERROR, _("Remote connection closed"));
       /* no return */
     case SERIAL_ERROR:
-      remote_unpush_target ();
-      throw_perror_with_name (TARGET_CLOSE_ERROR,
-			      _("Remote communication error.  "
-				"Target disconnected."));
+      unpush_and_perror (_("Remote communication error.  "
+			   "Target disconnected."));
       /* no return */
     case SERIAL_TIMEOUT:
       break;
@@ -7071,10 +7086,8 @@ remote_serial_write (const char *str, int len)
 {
   if (serial_write (remote_desc, str, len))
     {
-      remote_unpush_target ();
-      throw_perror_with_name (TARGET_CLOSE_ERROR,
-			      _("Remote communication error.  "
-				"Target disconnected."));
+      unpush_and_perror (_("Remote communication error.  "
+			   "Target disconnected."));
     }
 }