This is the mail archive of the
archer@sourceware.org
mailing list for the Archer project.
Re: [RFC] Patch for gnats pr 2495
- From: Phil Muldoon <pmuldoon at redhat dot com>
- To: Tom Tromey <tromey at redhat dot com>
- Cc: Project Archer <archer at sourceware dot org>
- Date: Wed, 22 Oct 2008 15:54:05 +0100
- Subject: Re: [RFC] Patch for gnats pr 2495
- References: <48F344BB.2070204@redhat.com> <m3r66hbhvi.fsf@fleche.redhat.com>
Tom Tromey wrote:
"Phil" == Phil Muldoon <pmuldoon@redhat.com> writes:
Phil> This patch addresses that by gating access to std::terminate in an
Phil> inferior function call.
Sounds good. The patch looks nice! In fact the majority of my
comments are on the string constants :-
I've attached an updated patch. I think I caught all of your suggestions.
gdb/doc/ChangeLog
2008-10-22 Phil Muldoon <pmuldoon@redhat.com>
* gdb.texinfo (Calling): Add unwind-on-terminating-exception
flag descriptions.
gdb/ChangeLog
2008-10-22 Phil Muldoon <pmuldoon@redhat.com>
* infcall.c (show_unwind_on_terminating_exception_p): New
function.
(call_function_by_hand): Create breakpoint and clean-up call for
std::terminate.breakpoint. Add unwind_on_terminating_exception_p
gate. Pop frame on breakpoint hit.
(_initialize_infcall): Add add_setshow_boolean_cmd for
unwind-on-terminating-exception.
gdb/testsuite/ChangeLog
2008-10-22 Phil Muldoon <pmuldoon@redhat.com>
* gdb.cp/gdb2495.cc: New file.
* gdb.cp/gdb2495.exp: New file.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 67b5fac..1703c27 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -12169,6 +12169,12 @@ It is possible for the function you call via the @code{print} or
the function, or if you passed it incorrect arguments). What happens
in that case is controlled by the @code{set unwindonsignal} command.
+Similarly, with a C++ program it is possible for the function you
+call via the @code{print} or @code{call} command to generate an
+exception that is not handled due to the constraints of the dummy
+frame. What happens in that case is controlled by the
+@code{set unwind-on-terminating-exception} command.
+
@table @code
@item set unwindonsignal
@kindex set unwindonsignal
@@ -12185,6 +12191,23 @@ received.
@kindex show unwindonsignal
Show the current setting of stack unwinding in the functions called by
@value{GDBN}.
+
+@item set unwind-on-terminating-exception
+@kindex set unwind-on-terminating-exception
+@cindex unwind stack in called functions
+@cindex call dummy stack unwinding on unhandled exception.
+Set unwinding of the stack if a C++ exception is raised but unhandled
+while in a function that @value{GDBN} called in the program being
+debugged. If set to on (the default), @value{GDBN} unwinds the stack
+it created for the call and restores the context to what it was before
+the call. If set to off, @value{GDBN} the exception is delivered to
+the default C++ exception handler.
+
+@item show unwind-on-terminating-exception
+@kindex show unwind-on-terminating-exception
+Show the current setting of stack unwinding in the functions called by
+@value{GDBN}.
+
@end table
@cindex weak alias functions
diff --git a/gdb/infcall.c b/gdb/infcall.c
index 5cc068a..5749d20 100644
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -91,6 +91,28 @@ Unwinding of stack if a signal is received while in a call dummy is %s.\n"),
value);
}
+/* This boolean tells what gdb should do if a std::terminate call is
+ made while in a function called from gdb (call dummy).
+ As the confines of a single dummy stack prohibit out-of-frame
+ handlers from handling a raised exception, and as out-of-frame
+ handlers are common in C++, this can lead to no handler being found
+ by the unwinder, and a std::terminate call. This is a false positive.
+ If set, gdb unwinds the stack and restores the context to what it
+ was before the call.
+
+ The default is to unwind the frame if a std::terminate call is made.. */
+
+static int unwind_on_terminating_exception_p = 1;
+static void
+show_unwind_on_terminating_exception_p (struct ui_file *file, int from_tty,
+ struct cmd_list_element *c,
+ const char *value)
+
+{
+ fprintf_filtered (file, _("\
+Unwind stack if a C++ exception is unhandled while in a call dummy is %s.\n"),
+ value);
+}
/* Perform the standard coercions that are specified
for arguments to be passed to C or Ada functions.
@@ -328,6 +350,8 @@ call_function_by_hand (struct value *function, int nargs, struct value **args)
struct cleanup *args_cleanup;
struct frame_info *frame;
struct gdbarch *gdbarch;
+ struct breakpoint *terminate_bp = 0;
+ struct minimal_symbol *tm;
if (TYPE_CODE (ftype) == TYPE_CODE_PTR)
ftype = check_typedef (TYPE_TARGET_TYPE (ftype));
@@ -652,6 +676,27 @@ call_function_by_hand (struct value *function, int nargs, struct value **args)
/* Now proceed, having reached the desired place. */
clear_proceed_status ();
+ /* Create a breakpoint in std::terminate.
+ If a C++ exception is raised in the dummy-frame, and the
+ exception handler is (normally, and expected to be) out-of-frame,
+ the default C++ handler will (wrongly) be called in an inferior
+ function call. This is wrong, as an exception can be normally
+ and legally handled out-of-frame. The confines of the dummy frame
+ prevent the unwinder from finding the correct handler (or any
+ handler, unless it is in-frame). The default handler calls
+ std::terminate. This will kill the inferior. Assert that
+ terminate should never be called in an inferior function
+ call. Place a momentary breakpoint in the std::terminate function
+ and if triggered in the call, rewind */
+ if (unwind_on_terminating_exception_p)
+ {
+ tm = lookup_minimal_symbol ("std::terminate()", NULL, NULL);
+ if (tm != NULL)
+ terminate_bp = set_momentary_breakpoint_at_pc
+ (SYMBOL_VALUE_ADDRESS (tm), bp_breakpoint);
+ make_cleanup_delete_breakpoint (terminate_bp);
+ }
+
/* Execute a "stack dummy", a piece of code stored in the stack by
the debugger to be executed in the inferior.
@@ -778,6 +823,30 @@ Evaluation of the expression containing the function (%s) will be abandoned."),
previously selected frame), would write the registers
from the inf_status (which is wrong), and would do other
wrong things. */
+
+ /* Check if unwind on terminating exception behaviour is on */
+ if (unwind_on_terminating_exception_p)
+ {
+ /* Check that the breakpoint is our special std::terminate
+ breakpoint. If it is, we do not want to kill the inferior
+ in an inferior function call. Rewind, and warn the user */
+
+ if ((terminate_bp != NULL) &&
+ (inferior_thread()->stop_bpstat->breakpoint_at->address
+ == terminate_bp->loc->address))
+
+
+ {
+ frame_pop (get_current_frame ());
+ error (_("\
+The program being debugged entered a std::terminate call which would\n\
+have terminated the program being debugged. GDB has restored the\n\
+context to what it was before the call.\n\
+To change this behaviour use \"set unwind-on-terminating-exception off\"\n\
+Evaluation of the expression containing the function (%s) will be abandoned."),
+ name);
+ }
+ }
discard_cleanups (inf_status_cleanup);
discard_inferior_status (inf_status);
/* The following error message used to say "The expression
@@ -878,4 +947,19 @@ The default is to stop in the frame where the signal was received."),
NULL,
show_unwind_on_signal_p,
&setlist, &showlist);
+
+ add_setshow_boolean_cmd ("unwind-on-terminating-exception", no_class,
+ &unwind_on_terminating_exception_p, _("\
+Set unwinding of stack if a std::terminate() call originates from\n\
+the default C++ exception handler."), _("\
+Show unwinding of stack if a std::terminate() call originates from\n\
+the default C++ exception handler."), _("\
+The unwind on terminating exception flag lets the user determine\n\
+what gdb should do if a std::terminate() call is made from the\n\
+default exception handler.\n\
+The default is to unwind the frame."),
+ NULL,
+ show_unwind_on_terminating_exception_p,
+ &setlist, &showlist);
+
}
diff --git a/gdb/testsuite/gdb.cp/Makefile.in b/gdb/testsuite/gdb.cp/Makefile.in
index f4a989c..6d0f809 100644
--- a/gdb/testsuite/gdb.cp/Makefile.in
+++ b/gdb/testsuite/gdb.cp/Makefile.in
@@ -4,7 +4,7 @@ srcdir = @srcdir@
EXECUTABLES = ambiguous annota2 anon-union cplusfuncs cttiadd \
derivation inherit local member-ptr method misc \
overload ovldbreak ref-typ ref-typ2 templates userdef virtfunc namespace \
- ref-types ref-params method2
+ ref-types ref-params method2 gdb2495
all info install-info dvi install uninstall installcheck check:
@echo "Nothing to be done for $@..."
diff --git a/gdb/testsuite/gdb.cp/gdb2495.cc b/gdb/testsuite/gdb.cp/gdb2495.cc
new file mode 100644
index 0000000..4df265f
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/gdb2495.cc
@@ -0,0 +1,90 @@
+/* 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/>.
+ */
+
+#include <iostream>
+#include <signal.h>
+
+using namespace std;
+
+class SimpleException
+{
+
+public:
+
+ void raise_signal (int dummy)
+ {
+ if (dummy > 0)
+ raise(SIGABRT);
+ }
+
+ int no_throw_function ()
+ {
+ return 1;
+ }
+
+ void throw_function ()
+ {
+ throw 1;
+ }
+
+ int throw_function_with_handler ()
+ {
+ try
+ {
+ throw 1;
+ }
+ catch (...)
+ {
+ cout << "Handled" << endl;
+ }
+
+ return 2;
+ }
+
+ void call_throw_function_no_handler ()
+ {
+ throw_function ();
+ }
+
+ void call_throw_function_handler ()
+ {
+ throw_function_with_handler ();
+ }
+};
+SimpleException exceptions;
+
+int
+main()
+{
+ // Have to call all these functions
+ // so not optimized away.
+ exceptions.raise_signal (-1);
+ exceptions.no_throw_function ();
+ exceptions.throw_function_with_handler ();
+ exceptions.call_throw_function_handler ();
+ try
+ {
+ exceptions.throw_function ();
+ exceptions.call_throw_function_no_handler ();
+ }
+ catch (...)
+ {
+ }
+ return 0;
+}
+
diff --git a/gdb/testsuite/gdb.cp/gdb2495.exp b/gdb/testsuite/gdb.cp/gdb2495.exp
new file mode 100644
index 0000000..5afeb1b
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/gdb2495.exp
@@ -0,0 +1,160 @@
+# 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/>.
+
+
+# In gdb inferior function calls, if a C++ exception is raised in the
+# dummy-frame, and the exception handler is (normally, and expected to
+# be) out-of-frame, the default C++ handler will (wrongly) be called
+# in an inferior function call.
+# This is incorrect as an exception can normally and legally be handled
+# out-of-frame. The confines of the dummy frame prevent the unwinder
+# from finding the correct handler (or any handler, unless it is
+# in-frame). The default handler calls std::terminate. This will kill
+# the inferior. Assert that terminate should never be called in an
+# inferior function call. These tests test the functionality around
+# unwinding that sequence and also tests the flag behaviour gating this
+# functionality.
+
+# This test is largley based off gdb.base/callfuncs.exp.
+
+if $tracelevel then {
+ strace $tracelevel
+}
+
+if { [skip_cplus_tests] } { continue }
+
+set prms_id 2495
+set bug_id 0
+
+set testfile "gdb2495"
+set srcfile ${testfile}.cc
+set binfile $objdir/$subdir/$testfile
+
+# Create and source the file that provides information about the compiler
+# used to compile the test case.
+if [get_compiler_info ${binfile} "c++"] {
+ return -1
+}
+
+if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug c++}] != "" } {
+ untested gdb2495.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
+}
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+if ![runto_main] then {
+ perror "couldn't run to main"
+ continue
+}
+
+# See http://sources.redhat.com/gdb/bugs/2495
+
+# Test normal baseline behaviour. Call a function that
+# does not raise an exception ...
+gdb_test "p exceptions.no_throw_function()" " = 1"
+# And one that does but handles it in-frame ...
+gdb_test "p exceptions.throw_function_with_handler()" " = 2"
+# Both should return normally.
+
+# Test basic unwind. Call a function that raises an exception but
+# does not handle it. It should be rewound ...
+gdb_test "p exceptions.throw_function()" \
+ "The program being debugged entered a std::terminate call .*" \
+ "Call a function that raises an exception without a handler."
+
+# Make sure that after rewinding we are back at the call parent.
+gdb_test "bt" \
+ "#0 main.*" \
+ "bt after returning from a popped frame"
+
+# Make sure the only breakpoint is the one set via the runto_main
+# call and that the std::terminate breakpoint has evaporated and
+# cleaned-up.
+gdb_test "info breakpoints" \
+ "gdb.cp/gdb2495\.cc.*"
+
+# Turn off this new behaviour ...
+send_gdb "set unwind-on-terminating-exception off\n"
+gdb_expect {
+ -re "$gdb_prompt $" {pass "set unwind-on-terminating-exception"}
+ timeout {fail "(timeout) set unwind-on-terminating-exception"}
+}
+
+# Check that it is turned off ...
+gdb_test "show unwind-on-terminating-exception" \
+ "exception is unhandled while in a call dummy is off.*" \
+ "Turn off unwind on terminating exception flag"
+
+# Check that the old behaviour is restored.
+gdb_test "p exceptions.throw_function()" \
+ "The program being debugged was signaled while in a function .*" \
+ "Call a function that raises an exception with unwinding off.."
+
+
+# Restart back at main
+if ![runto_main] then {
+ perror "couldn't run to main"
+ continue
+}
+
+
+# Check to see if our new behaviour alters the unwind signal
+# behaviour. It should not. Test both on and off states.
+
+# Turn on unwind on signal behaviour ...
+send_gdb "set unwindonsignal on\n"
+gdb_expect {
+ -re "$gdb_prompt $" {pass "set unwindonsignal on"}
+ timeout {fail "(timeout) set unwindonsignal on"}
+}
+
+# Check that it is turned on ...
+gdb_test "show unwindonsignal" \
+ "signal is received while in a call dummy is on.*" \
+ "Turn on unwind on signal"
+
+# Check to see if new behaviour interferes with
+# normal signal handling in inferior function calls.
+gdb_test "p exceptions.raise_signal(1)" \
+ "To change this behavior use \"set unwindonsignal off\".*"
+
+# And reverse. Turn off
+send_gdb "set unwindonsignal off\n"
+gdb_expect {
+ -re "$gdb_prompt $" {pass "set unwindonsignal off"}
+ timeout {fail "(timeout) set unwindonsignal off"}
+}
+
+# Check that it is turned off ...
+gdb_test "show unwindonsignal" \
+ "signal is received while in a call dummy is off.*" \
+ "Turn off unwind on signal"
+
+# Check to see if new behaviour interferes with
+# normal signal handling in inferior function calls.
+gdb_test "p exceptions.raise_signal(1)" \
+ "To change this behavior use \"set unwindonsignal on\".*"