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

[dje at google dot com (Doug Evans)]

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