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

Pedro Alves
2013-04-09T12:19:47Z

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."));
}
}