[PATCH] Avoid potencially-stale errno usage (was: Re: Include putpkt in TRY_CATCH. PR gdb/15275)

Pedro Alves
2013-04-08T17:57:26Z

On 03/28/2013 05:07 PM, Pedro Alves wrote:
> (
> There's a latent bug in the patch that that throw_perror_with_name
> call assumes error is still set to the right error, although
> remote_unpush_target is called in between. I'm copying this
> from preexisting code, and we can fix both at once.)
>
> if (serial_write (remote_desc, str, len))
> {
> remote_unpush_target ();
> throw_perror_with_name (TARGET_CLOSE_ERROR,
> )

Fixing this before it ends up forgotten and bites us at some
point.

Comments?

------------
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/
2013-04-08 Pedro Alves <palves@redhat.com>

* remote.c (unpush_and_perror): New function.
(readchar, remote_serial_write): Use it.

---

gdb/remote.c | 32 ++++++++++++++++++++++----------
1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index 740324b..e60ff78 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
@@ -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"));
/* 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 +7085,8 @@ 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."));
}
}