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Re: [RFA] fix popping of dummy frame if inferior gets signal with unwindonsignal


I don't understand why calling dummy_frame_pop directly works,
but calling frame_pop doesn't work.  Doesn't frame_pop call
dummy_frame_pop?  If not, what prevents it?

Doug Evans wrote:
Hi.  This fixes a bug where a signal in an inferior function call with
unwindonsignal set doesn't remove the dummy frame from dummy_frame_stack.
A testcase is included to exercise the bug.

It also adds a comment to clear up something that was a bit confusing
at first.  The lone frame_pop isn't enough to properly restore program
state, but things still work because registers (and thus stack) get
restored from inf_status.

Tested on i386-linux.

Ok to check in?

2008-11-15 Doug Evans <dje@google.com>

	* infcall.c (call_function_by_hand): Properly pop the dummy frame
	if the inferior gets a signal and unwindonsignal is set.

	* gdb.base/unwindonsignal.c: New file.
	* gdb.base/unwindonsignal.exp: New file.

Index: infcall.c
===================================================================
RCS file: /cvs/src/src/gdb/infcall.c,v
retrieving revision 1.105
diff -u -p -u -p -r1.105 infcall.c
--- infcall.c 12 Nov 2008 00:39:28 -0000 1.105
+++ infcall.c 15 Nov 2008 22:08:54 -0000
@@ -357,7 +358,10 @@ call_function_by_hand (struct value *fun
/* Save the caller's registers so that they can be restored once the
callee returns. To allow nested calls the registers are (further
down) pushed onto a dummy frame stack. Include a cleanup (which
- is tossed once the regcache has been pushed). */
+ is tossed once the regcache has been pushed).
+ NOTE: If the inferior gets a signal and unwindonsignal is set,
+ then this regcache is not used to restore target regs. Instead
+ the regcache in inf_status is used. */
caller_regcache = frame_save_as_regcache (frame);
caller_regcache_cleanup = make_cleanup_regcache_xfree (caller_regcache);
@@ -746,8 +749,12 @@ The program being debugged exited while /* The user wants the context restored. */
/* We must get back to the frame we were before the
- dummy call. */
- frame_pop (get_current_frame ());
+ dummy call.
+ NOTE: This discards the regcache recorded in the dummy frame
+ but that's ok, the registers will get restored from the
+ regcache in inf_status (which gets called by a cleanup). */
+ dummy_frame_pop (dummy_id);
+ reinit_frame_cache ();
/* FIXME: Insert a bunch of wrap_here; name can be very
long if it's a C++ name with arguments and stuff. */
Index: testsuite/gdb.base/unwindonsignal.c
===================================================================
RCS file: testsuite/gdb.base/unwindonsignal.c
diff -N testsuite/gdb.base/unwindonsignal.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/unwindonsignal.c 16 Nov 2008 01:11:22 -0000
@@ -0,0 +1,49 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2008 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/>. */
+
+/* Support program for testing handling of unwindonsignal. */
+
+#include <stdio.h>
+#include <signal.h>
+#include <unistd.h>
+
+/* This function is handcalled from unwindonsignal.exp. */
+
+void
+gen_signal ()
+{
+ /* According to sigall.exp, SIGABRT is always supported,
+ so try that first. */
+#ifdef SIGABRT
+ kill (getpid (), SIGABRT);
+#endif
+#ifdef SIGSEGV
+ kill (getpid (), SIGSEGV);
+#endif
+ /* If we get here we couldn't generate a signal, tell dejagnu. */
+ printf ("no signal\n");
+}
+
+int
+main ()
+{
+#ifdef usestubs
+ set_debug_traps ();
+ breakpoint ();
+#endif
+ return 0;
+}
Index: testsuite/gdb.base/unwindonsignal.exp
===================================================================
RCS file: testsuite/gdb.base/unwindonsignal.exp
diff -N testsuite/gdb.base/unwindonsignal.exp
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/unwindonsignal.exp 16 Nov 2008 01:11:22 -0000
@@ -0,0 +1,94 @@
+# Copyright 2008 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/>.
+
+if $tracelevel then {
+ strace $tracelevel
+}
+
+if [target_info exists gdb,noinferiorio] {
+ verbose "Skipping unwindonsignal.exp because of no fileio capabilities."
+ continue
+}
+
+set prms_id 0
+set bug_id 0
+
+set testfile "unwindonsignal"
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+
+if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+ untested unwindonsignal.exp
+ return -1
+}
+
+# Some targets can't do function calls, so don't even bother with this
+# test.
+if [target_info exists gdb,cannot_call_functions] {
+ setup_xfail "*-*-*" 2416
+ fail "This target can not call functions"
+ continue
+}
+
+# Start with a fresh gdb.
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+if { ![runto_main] } {
+ fail "Can't run to main"
+ return 0
+}
+
+# Turn on unwindonsignal.
+gdb_test "set unwindonsignal on" \
+ "" \
+ "setting unwindonsignal"
+gdb_test "show unwindonsignal" \
+ "Unwinding of stack .* is on." \
+ "showing unwindonsignal"
+
+# Call function (causing the program to get a signal), and see if gdb handles
+# it properly.
+gdb_test_multiple "call gen_signal ()" \
+ "unwindonsignal, inferior function call signaled" {
+ -re "\[\r\n\]*no signal\[\r\n\]+$gdb_prompt $" {
+ unsupported "unwindonsignal, inferior function call signaled"
+ return 0
+ }
+ -re "\[\r\n\]*The program being debugged was signaled.*\[\r\n\]+$gdb_prompt $" {
+ pass "unwindonsignal, inferior function call signaled"
+ }
+}
+
+# Verify the stack got unwound.
+gdb_test "bt" \
+ "#0 *main \\(.*\\) at .*" \
+ "unwindonsignal, stack unwound"
+
+# Verify the dummy frame got removed from dummy_frame_stack.
+gdb_test_multiple "maint print dummy-frames" \
+ "unwindonsignal, dummy frame removed" {
+ -re "\[\r\n\]*.*stack=.*code=.*\[\r\n\]+$gdb_prompt $" {
+ fail "unwindonsignal, dummy frame removed"
+ }
+ -re "\[\r\n\]+$gdb_prompt $" {
+ pass "unwindonsignal, dummy frame removed"
+ }
+}
+
+return 0


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