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windows-nat: Report an error if ContinueDebugEvent() fails

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Using the 'catch-signal' test from the testsuite, on x86_64 Cygwin:

    $ ./gdb testsuite/outputs/gdb.base/catch-signal/catch-signal.exe
    [...]
    (gdb) catch signal
    Catchpoint 1 (standard signals)
    (gdb) r
    [...]
    Catchpoint 1 (signal SIGHUP), main () at
    ../../../gdb/testsuite/gdb.base/catch-signal.c:40
    40        raise (SIGHUP);               /* second HUP */
    (gdb) c
    Continuing.
    [hangs]

This is due to a defect in the way Cygwin signals are handled: When
handle_output_debug_string processes a Cygwin signal message, it re-writes
current_event.dwThreadId to reflect the thread that the signal will be delivered
to.

Subsequently, the call to ContinueDebugEvent will fail, because we're trying to
resume the wrong thread.  GDB is then stuck waiting forever for another event
that will never come.

This patch doesn't fix the problem, it just adds appropriate error handling.

Using error() seems appropriate here, if ContinueDebugEvent() fails, the
inferior is in an unknown state and we will probably not be debugging it
anymore.

With this patch applied, resuming the execution of the program now yields:

    $ ./gdb testsuite/outputs/gdb.base/catch-signal/catch-signal.exe
    [...]
    (gdb) catch signal
    Catchpoint 1 (standard signals)
    (gdb) r
    [...]
    Catchpoint 1 (signal SIGHUP), main () at
    ../../../gdb/testsuite/gdb.base/catch-signal.c:40
    40        raise (SIGHUP);               /* second HUP */
    (gdb) c
    Continuing.
    main () at ../../../gdb/testsuite/gdb.base/catch-signal.c:40
    40        raise (SIGHUP);               /* second HUP */
    Failed to resume program execution (ContinueDebugEvent failed, error 87)
    (gdb)

gdb/ChangeLog:

2015-04-22  Jon Turney  <jon.turney@dronecode.org.uk>

	* windows-nat.c (windows_continue): Report an error if
	ContinueDebugEvent() fails.
This commit is contained in:
Jon Turney 2015-04-15 21:37:11 +01:00
parent 23942819fc
commit 68ffc90245
2 changed files with 10 additions and 0 deletions
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5
gdb/ChangeLog
View File

@ -1,3 +1,8 @@
2015-04-22 Jon Turney <jon.turney@dronecode.org.uk>
* windows-nat.c (windows_continue): Report an error if
ContinueDebugEvent() fails.
2015-04-16 Jon Turney <jon.turney@dronecode.org.uk>
* windows-nat.c (windows_resume): Fix misspelling in debug output.

5
gdb/windows-nat.c
View File

@ -1160,6 +1160,11 @@ windows_continue (DWORD continue_status, int id, int killed)
current_event.dwThreadId,
continue_status);
if (!res)
error (_("Failed to resume program execution"
" (ContinueDebugEvent failed, error %u)"),
(unsigned int) GetLastError ());
debug_registers_changed = 0;
return res;
}