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Re: [PATCH v4] Implement $_exitsignal
- From: Sergio Durigan Junior <sergiodj at redhat dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: GDB Patches <gdb-patches at sourceware dot org>, Doug Evans <dje at google dot com>
- Date: Thu, 03 Oct 2013 02:48:19 -0300
- Subject: Re: [PATCH v4] Implement $_exitsignal
- Authentication-results: sourceware.org; auth=none
- References: <m3six3nxr6 dot fsf at redhat dot com> <524B1648 dot 8090805 at redhat dot com>
On Tuesday, October 01 2013, Pedro Alves wrote:
> On 09/17/2013 06:50 PM, Sergio Durigan Junior wrote:
>> +# Running until the end.
>> +gdb_test "run" "\\\[Inferior .* exited normally\\\]" "Run inferior until the end"
>> +
>
> I was about to OK the whole patch, but I noticed this: :-/
>
> "run" won't work with "target remote". Please try the native-gdbserver.exp
> board.
Ops, thanks for the catch. I fixed it by checking for is_remote target
and the presence of $use_gdb_stub. I guess it's enough. Tested on
native-{,extended-,stdio-}gdbserver.
> As long as there's going to be another round, I think the code
> could be simplified. All that logic that clears the variables:
>
> + /* The inferior did not die because of an uncaught signal,
> + therefore we must clear $_exitsignal. */
> + clear_internalvar (lookup_internalvar ("_exitsignal"));
> + }
> +
> + /* Clear the $_exitcode internal variable, because there is no way
> + the inferior could have exited and generated a corefile. */
> + clear_internalvar (lookup_internalvar ("_exitcode"));
>
> could be replaced by this pattern:
>
> /* Clear these first. */
> clear $_exitsignal;
> clear $_exitcode;
>
> if (blah)
> set $_exitsignal;
> if (bleh)
> set $_exitcode;
>
> IOW, unconditionally clear both variables first, then set
> the one that makes sense.
>
> The same pattern can be done in both corelow.c and infrun.c.
>
> (those clears could be put in a small helper, as they'll
> be done in two places).
Done. I was not sure where to put the declaration of this new helper
function, so I decided for gdb/utils.h. Not sure it's a good place,
though. Let me know what you think and I can change it if needed.
Thanks,
--
Sergio
gdb/
2013-10-02 Sergio Durigan Junior <sergiodj@redhat.com>
* NEWS: Mention new convenience variable $_exitsignal.
* corelow.c (core_open): Reset exit convenience variables. Set
$_exitsignal to the uncaught signal which generated the corefile.
* infrun.c (handle_inferior_event): Reset exit convenience
variables. Set $_exitsignal for TARGET_WAITKIND_SIGNALLED.
(clear_exit_convenience_vars): New function.
* utils.h (clear_exit_convenience_vars): New prototype.
gdb/testsuite/
2013-10-02 Sergio Durigan Junior <sergiodj@redhat.com>
* gdb.base/corefile.exp: Test whether $_exitsignal is set and
$_exitcode is void when opening a corefile.
* gdb.base/exitsignal.exp: New file.
* gdb.base/segv.c: Likewise.
* gdb.base/normal.c: Likewise.
gdb/doc/
2013-10-02 Sergio Durigan Junior <sergiodj@redhat.com>
* gdb.texinfo (Convenience Variables): Document $_exitsignal.
Update entry for $_exitcode.
diff --git a/gdb/NEWS b/gdb/NEWS
index 5a9f8db..90311c2 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -119,6 +119,10 @@ show range-stepping
* The exception-related catchpoints, like "catch throw", now accept a
regular expression which can be used to filter exceptions by type.
+* The new convenience variable $_exitsignal is automatically set to
+ the terminating signal number when the program being debugged dies
+ due to an uncaught signal.
+
* MI changes
** The -trace-save MI command can optionally save trace buffer in Common
diff --git a/gdb/corelow.c b/gdb/corelow.c
index 7a5aaab..d1e7f6a 100644
--- a/gdb/corelow.c
+++ b/gdb/corelow.c
@@ -429,6 +429,9 @@ core_open (char *filename, int from_tty)
if (p)
printf_filtered (_("Core was generated by `%s'.\n"), p);
+ /* Clearing any previous state of convenience variables. */
+ clear_exit_convenience_vars ();
+
siggy = bfd_core_file_failing_signal (core_bfd);
if (siggy > 0)
{
@@ -446,6 +449,11 @@ core_open (char *filename, int from_tty)
printf_filtered (_("Program terminated with signal %s, %s.\n"),
gdb_signal_to_name (sig), gdb_signal_to_string (sig));
+
+ /* Set the value of the internal variable $_exitsignal,
+ which holds the signal uncaught by the inferior. */
+ set_internalvar_integer (lookup_internalvar ("_exitsignal"),
+ siggy);
}
/* Fetch all registers from core file. */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index cf6f7d3..63092eb 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -9751,8 +9751,64 @@ to match the format in which the data was printed.
@item $_exitcode
@vindex $_exitcode@r{, convenience variable}
-The variable @code{$_exitcode} is automatically set to the exit code when
-the program being debugged terminates.
+When the program being debugged terminates normally, @value{GDBN}
+automatically sets this variable to the exit code of the program, and
+resets @code{$_exitsignal} to @code{void}.
+
+@item $_exitsignal
+@vindex $_exitsignal@r{, convenience variable}
+When the program being debugged dies due to an uncaught signal,
+@value{GDBN} automatically sets this variable to that signal's number,
+and resets @code{$_exitcode} to @code{void}.
+
+To distinguish between whether the program being debugged has exited
+(i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
+@code{$_exitsignal} is not @code{void}), the convenience function
+@code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
+Functions}). For example, considering the following source code:
+
+@smallexample
+#include <signal.h>
+
+int
+main (int argc, char *argv[])
+@{
+ raise (SIGALRM);
+ return 0;
+@}
+@end smallexample
+
+A valid way of telling whether the program being debugged has exited
+or signalled would be:
+
+@smallexample
+(@value{GDBP}) define has_exited_or_signalled
+Type commands for definition of ``has_exited_or_signalled''.
+End with a line saying just ``end''.
+>if $_isvoid ($_exitsignal)
+ >echo The program has exited\n
+ >else
+ >echo The program has signalled\n
+ >end
+>end
+(@value{GDBP}) run
+Starting program:
+
+Program terminated with signal SIGALRM, Alarm clock.
+The program no longer exists.
+(@value{GDBP}) has_exited_or_signalled
+The program has signalled
+@end smallexample
+
+As can be seen, @value{GDBN} correctly informs that the program being
+debugged has signalled, since it calls @code{raise} and raises a
+@code{SIGALRM} signal. If the program being debugged had not called
+@code{raise}, then @value{GDBN} would report a normal exit:
+
+@smallexample
+(@value{GDBP}) has_exited_or_signalled
+The program has exited
+@end smallexample
@item $_exception
The variable @code{$_exception} is set to the exception object being
diff --git a/gdb/infrun.c b/gdb/infrun.c
index db0ad8d..e5056c5 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -3426,6 +3426,9 @@ handle_inferior_event (struct execution_control_state *ecs)
handle_vfork_child_exec_or_exit (0);
target_terminal_ours (); /* Must do this before mourn anyway. */
+ /* Clearing any previous state of convenience variables. */
+ clear_exit_convenience_vars ();
+
if (ecs->ws.kind == TARGET_WAITKIND_EXITED)
{
/* Record the exit code in the convenience variable $_exitcode, so
@@ -3440,7 +3443,38 @@ handle_inferior_event (struct execution_control_state *ecs)
print_exited_reason (ecs->ws.value.integer);
}
else
- print_signal_exited_reason (ecs->ws.value.sig);
+ {
+ struct regcache *regcache = get_thread_regcache (ecs->ptid);
+ struct gdbarch *gdbarch = get_regcache_arch (regcache);
+
+ if (gdbarch_gdb_signal_to_target_p (gdbarch))
+ {
+ /* Set the value of the internal variable $_exitsignal,
+ which holds the signal uncaught by the inferior. */
+ set_internalvar_integer (lookup_internalvar ("_exitsignal"),
+ gdbarch_gdb_signal_to_target (gdbarch,
+ ecs->ws.value.sig));
+ }
+ else
+ {
+ static int have_warned_signal_to_target = 0;
+
+ /* We don't have access to the target's method used for
+ converting between signal numbers (GDB's internal
+ representation <-> target's representation).
+ Therefore, we cannot do a good job at displaying this
+ information to the user. It's better to just warn
+ her about it, and give up. */
+ if (!have_warned_signal_to_target)
+ {
+ have_warned_signal_to_target = 1;
+ warning (_("\
+Cannot fill $_exitsignal with the correct signal number."));
+ }
+ }
+
+ print_signal_exited_reason (ecs->ws.value.sig);
+ }
gdb_flush (gdb_stdout);
target_mourn_inferior ();
@@ -7061,6 +7095,15 @@ save_inferior_ptid (void)
*saved_ptid_ptr = inferior_ptid;
return make_cleanup (restore_inferior_ptid, saved_ptid_ptr);
}
+
+/* See comment at utils.h. */
+
+void
+clear_exit_convenience_vars (void)
+{
+ clear_internalvar (lookup_internalvar ("_exitsignal"));
+ clear_internalvar (lookup_internalvar ("_exitcode"));
+}
/* User interface for reverse debugging:
diff --git a/gdb/testsuite/gdb.base/corefile.exp b/gdb/testsuite/gdb.base/corefile.exp
index 04ae969..72c7a4a 100644
--- a/gdb/testsuite/gdb.base/corefile.exp
+++ b/gdb/testsuite/gdb.base/corefile.exp
@@ -142,6 +142,16 @@ gdb_test "print coremaker_ro" "\\\$$decimal = 201"
gdb_test "print func2::coremaker_local" "\\\$$decimal = \\{0, 1, 2, 3, 4\\}"
+# Test the presence and the correct values of $_exitsignal and
+# $_exitcode variables. The corefile is generated with a SIGABRT,
+# which is "6" in the Linux kernel.
+
+gdb_test "print \$_exitsignal" " = 6" \
+ "\$_exitsignal prints SIGABRT (6)"
+
+gdb_test "print \$_exitcode" " = void" \
+ "\$_exitcode is void"
+
# Somehow we better test the ability to read the registers out of the core
# file correctly. I don't think the other tests do this.
diff --git a/gdb/testsuite/gdb.base/exitsignal.exp b/gdb/testsuite/gdb.base/exitsignal.exp
new file mode 100644
index 0000000..3678fd8
--- /dev/null
+++ b/gdb/testsuite/gdb.base/exitsignal.exp
@@ -0,0 +1,102 @@
+# Copyright 2013 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# This test checks both $_exitcode and $_exitsignal variables. The
+# purpose of this checking is to ensure that the variables are
+# mutually exclusive, i.e., that when $_exitsignal is set, $_exitcode
+# is not, and vice-versa. This mutual exclusion happens because if an
+# inferior exited (either successfuly or not), it certainly was not
+# killed by a signal. However, if it was killed by an uncaught
+# signal, then there is no way for it to have exited.
+
+standard_testfile segv.c
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+ return -1
+}
+
+# Run to main
+if { ![runto_main] } {
+ return -1
+}
+
+# Print $_exitsignal. It should be void now, because nothing
+# happened.
+gdb_test "print \$_exitsignal" " = void" \
+ "\$_exitsignal is void before running"
+
+# Just to guarantee, making sure that $_exitcode is also void.
+gdb_test "print \$_exitcode" " = void" \
+ "\$_exitcode is void before running"
+
+# Trigger SIGSEGV.
+gdb_test "continue" "Program received signal SIGSEGV.*" "trigger SIGSEGV"
+
+# Continue until the end.
+gdb_test "continue" "Program terminated with signal SIGSEGV.*" \
+ "program terminated with SIGSEGV"
+
+# Now, print $_exitsignal again. It should be 11 (SIGSEGV).
+gdb_test "print \$_exitsignal" " = 11" \
+ "\$_exitsignal is 11 (SIGSEGV) after SIGSEGV."
+
+# And $_exitcode should still be void, since the inferior died because
+# of a signal, and did not return.
+gdb_test "print \$_exitcode" " = void" \
+ "\$_exitcode is still void after SIGSEGV"
+
+# Re-run to main, i.e., restart the executable.
+rerun_to_main
+
+# Print the $_exitsignal again. Even in this normal scenario, it
+# should still contain the signal triggered in the other run.
+gdb_test "print \$_exitsignal" " = 11" \
+ "\$_exitsignal is 11 (SIGSEGV) after restarting the inferior"
+
+# And, again, print $_exitcode.
+gdb_test "print \$_exitcode" " = void" \
+ "\$_exitcode is still void after restarting the inferior"
+
+#
+if { [is_remote target] && [target_info exists use_gdb_stub] } then {
+ continue
+}
+
+# Now we test the behaviour of $_exit{code,signal} during a normal
+# inferior execution.
+standard_testfile normal.c
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+ return -1
+}
+
+# Checking $_exitsignal and $_exitcode, both should be void before the
+# inferior is executed.
+gdb_test "print \$_exitsignal" " = void" \
+ "\$_exitsignal is void before normal inferior is executed"
+gdb_test "print \$_exitcode" " = void" \
+ "\$_exitcode is void before normal inferior is executed"
+
+# Running until the end.
+gdb_test "run" "\\\[Inferior .* exited normally\\\]" "Run inferior until the end"
+
+# Checking $_exitcode. It should be 0.
+gdb_test "print \$_exitcode" " = 0" \
+ "\$_exitcode is zero after normal inferior is executed"
+
+# Checking $_exitsignal. It should still be void, since the inferior
+# has not received any signal.
+gdb_test "print \$_exitsignal" " = void" \
+ "\$_exitsignal is still void after normal inferior is executed"
diff --git a/gdb/testsuite/gdb.base/normal.c b/gdb/testsuite/gdb.base/normal.c
new file mode 100644
index 0000000..4aa7c45
--- /dev/null
+++ b/gdb/testsuite/gdb.base/normal.c
@@ -0,0 +1,24 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2013 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+/* This test is just a normal return 0. */
+
+int
+main (int argc, char *argv[])
+{
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.base/segv.c b/gdb/testsuite/gdb.base/segv.c
new file mode 100644
index 0000000..8991f4d
--- /dev/null
+++ b/gdb/testsuite/gdb.base/segv.c
@@ -0,0 +1,29 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2013 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+/* This test can be used just to generate a SIGSEGV. */
+
+#include <signal.h>
+
+int
+main (int argc, char *argv[])
+{
+ /* Generating a SIGSEGV. */
+ raise (SIGSEGV);
+
+ return 0;
+}
diff --git a/gdb/utils.h b/gdb/utils.h
index 3492f09..74d886f 100644
--- a/gdb/utils.h
+++ b/gdb/utils.h
@@ -331,6 +331,12 @@ extern void vwarning (const char *, va_list args) ATTRIBUTE_PRINTF (1, 0);
void *hashtab_obstack_allocate (void *data, size_t size, size_t count);
void dummy_obstack_deallocate (void *object, void *data);
+/* This function clears the convenience variables associated with the
+ exit of the inferior. Currently, those variables are $_exitcode
+ and $_exitsignal. */
+
+extern void clear_exit_convenience_vars (void);
+
#ifdef HAVE_WAITPID
extern pid_t wait_to_die_with_timeout (pid_t pid, int *status, int timeout);
#endif