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[PATCH 1/2] Fix "info break" + "catch catch" + -static-{libstdc++,libgcc}
- From: Pedro Alves <palves at redhat dot com>
- To: gdb-patches at sourceware dot org
- Date: Fri, 5 Jul 2019 17:00:54 +0100
- Subject: [PATCH 1/2] Fix "info break" + "catch catch" + -static-{libstdc++,libgcc}
- References: <20190705160055.13355-1-palves@redhat.com>
If you debug current GDB, set a "catch catch/throw/rethrow"
catchpoint, and then do "info breakpoints", the top GDB hits an
internal error:
(top-gdb) catch catch
Catchpoint 1 (catch)
(top-gdb) info breakpoints
Num Type Disp Enb Address What
1 breakpoint keep y src/gdb/breakpoint.c:6040: internal-error: void print_one_breakpoint_location(breakpoint*, bp_location*, int, bp_location**, int): Assertion `b->loc == NULL || b->loc->next == NULL' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n)
The assertion in question is asserting that a breakpoint with a
print_one method only has one location, and it fails because this
catchpoint ends up with two locations.
Internally, "catch catch" sets a breakpoint at __cxa_begin_catch. If
we do that manually, we see the locations:
(top-gdb) b -qualified __cxa_begin_catch
Breakpoint 2 at 0xb122b0 (2 locations)
(top-gdb) info breakpoints
Num Type Disp Enb Address What
2 breakpoint keep y <MULTIPLE>
2.1 y 0x0000000000b122b0 <__cxa_begin_catch>
2.2 y 0x00007ffff2f4ddb0 in __cxxabiv1::__cxa_begin_catch(void*) at ../../../../libstdc++-v3/libsupc++/eh_catch.cc:41
Note that I had used -qualified. It seems strange that we get a
location for a namespaced symbol, but that happens because the minimal
symbol for that address is indeed called __cxa_begin_catch.
The real issue is that gdb is linked with
-static-libgcc/-static-libstdc++. And then, it _also_ ends up with
shared libstc++ loaded:
(top-gdb) info sharedlibrary stdc++
From To Syms Read Shared Object Library
0x00007ffff2f4b380 0x00007ffff2ffc018 Yes /lib64/libstdc++.so.6
Location 2.2 is set within libstdc++.so.6's range:
(top-gdb) p 0x00007ffff2f4b380 <= 0x00007ffff2f4ddb0 && 0x00007ffff2f4ddb0 < 0x00007ffff2ffc018
$1 = true
So due to -static-lib*, we end up with _two_ copies of the
__cxa_begin_catch code:
(top-gdb) disassemble 0x0000000000b122b0
Dump of assembler code for function __cxa_begin_catch:
0x0000000000b122b0 <+0>: push %rbx
0x0000000000b122b1 <+1>: mov %rdi,%rbx
0x0000000000b122b4 <+4>: callq 0xb11a80 <__cxa_get_globals>
0x0000000000b122b9 <+9>: movabs $0xb8b1aabcbcd4d500,%rdx
...
(top-gdb) disassemble 0x00007ffff2f4ddb0
Dump of assembler code for function __cxxabiv1::__cxa_begin_catch(void*):
0x00007ffff2f4ddb0 <+0>: push %rbx
0x00007ffff2f4ddb1 <+1>: mov %rdi,%rbx
0x00007ffff2f4ddb4 <+4>: callq 0x7ffff2f4a090 <__cxa_get_globals@plt>
0x00007ffff2f4ddb9 <+9>: movabs $0xb8b1aabcbcd4d500,%rdx
...
I think we end up with libstdc++.so.6 loaded because
libsource-highlight.so depends on it.
Irrespective of whether it's a good idea to use
-static-libgcc/-static-libstdc++, GDB should not crash. Since there
are two copies of the code, it seems right to have more than one
location. So the fix is just to remove the assertion.
A testcase is included, which mimics the scenerio described above,
with binary linked with -static-lib{stdc++,gcc} and a shared library
that is linked normally, along with other combinations for good
measure.
gdb/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>
* breakpoint.c (print_one_breakpoint_location): Remove
single-location assert.
gdb/testsuite/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>
* gdb.cp/except-multi-location-lib.cc: New.
* gdb.cp/except-multi-location-main.cc: New.
* gdb.cp/except-multi-location.exp: New.
---
gdb/breakpoint.c | 8 +-
gdb/testsuite/gdb.cp/except-multi-location-lib.cc | 25 +++++++
gdb/testsuite/gdb.cp/except-multi-location-main.cc | 36 +++++++++
gdb/testsuite/gdb.cp/except-multi-location.exp | 87 ++++++++++++++++++++++
4 files changed, 149 insertions(+), 7 deletions(-)
create mode 100644 gdb/testsuite/gdb.cp/except-multi-location-lib.cc
create mode 100644 gdb/testsuite/gdb.cp/except-multi-location-main.cc
create mode 100644 gdb/testsuite/gdb.cp/except-multi-location.exp
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index b49be762a2f..d508921fdc5 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -6033,13 +6033,7 @@ print_one_breakpoint_location (struct breakpoint *b,
/* 5 and 6 */
if (b->ops != NULL && b->ops->print_one != NULL)
- {
- /* Although the print_one can possibly print all locations,
- calling it here is not likely to get any nice result. So,
- make sure there's just one location. */
- gdb_assert (b->loc == NULL || b->loc->next == NULL);
- b->ops->print_one (b, last_loc);
- }
+ b->ops->print_one (b, last_loc);
else
switch (b->type)
{
diff --git a/gdb/testsuite/gdb.cp/except-multi-location-lib.cc b/gdb/testsuite/gdb.cp/except-multi-location-lib.cc
new file mode 100644
index 00000000000..8767d756b33
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/except-multi-location-lib.cc
@@ -0,0 +1,25 @@
+/* Copyright 2019 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/>. */
+
+void
+trycatch_lib ()
+{
+ try
+ {
+ throw 1;
+ }
+ catch (...)
+ {
+ }
+}
diff --git a/gdb/testsuite/gdb.cp/except-multi-location-main.cc b/gdb/testsuite/gdb.cp/except-multi-location-main.cc
new file mode 100644
index 00000000000..161897a22ee
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/except-multi-location-main.cc
@@ -0,0 +1,36 @@
+/* Copyright 2019 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/>. */
+
+extern void trycatch_lib ();
+
+void
+trycatch_main ()
+{
+ try
+ {
+ throw 1;
+ }
+ catch (...)
+ {
+ }
+}
+
+int
+main ()
+{
+ trycatch_lib ();
+ trycatch_main ();
+
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.cp/except-multi-location.exp b/gdb/testsuite/gdb.cp/except-multi-location.exp
new file mode 100644
index 00000000000..60d6d0b9351
--- /dev/null
+++ b/gdb/testsuite/gdb.cp/except-multi-location.exp
@@ -0,0 +1,87 @@
+# Copyright 2019 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/>.
+
+# Regression test for a GDB internal error that would trigger if a
+# "catch catch" catchpoint ended up with multiple locations. This
+# testcase exercises that scenario by building the binary with
+# -static-libgcc/-static-libstdc++ and a shared library that depends
+# on the libstc++.so DSO (which is how GDB was built and revealed the
+# bug), and vice versa.
+
+if {[skip_shlib_tests]} {
+ return 0
+}
+
+# STATIC_BIN indicates whether to build the main binary with
+# -static-libgcc/-static-libstdc++. STATIC_LIB is the same, but for
+# the shared library.
+proc test_multi_libstdcpp {static_bin static_lib} {
+ global srcdir subdir
+ global decimal hex
+
+ # Library file.
+ set libname "except-multi-location-lib"
+ set srcfile_lib ${srcdir}/${subdir}/${libname}.cc
+ set binfile_lib [standard_output_file ${libname}-$static_bin-$static_lib.so]
+ set lib_flags {debug c++}
+ if {$static_lib} {
+ lappend lib_flags additional_flags=-static-libgcc additional_flags=-static-libstdc++
+ }
+
+ # Binary file.
+ set testfile "except-multi-location-main"
+ set srcfile ${srcdir}/${subdir}/${testfile}.cc
+ set binfile [standard_output_file ${testfile}-$static_bin-$static_lib]
+ set bin_flags [list debug c++ shlib=${binfile_lib}]
+ if {$static_bin} {
+ lappend bin_flags additional_flags=-static-libgcc additional_flags=-static-libstdc++
+ }
+
+ if { [gdb_compile_shlib ${srcfile_lib} ${binfile_lib} $lib_flags] != ""
+ || [gdb_compile ${srcfile} ${binfile} executable $bin_flags] != "" } {
+ untested "failed to compile"
+ return -1
+ }
+
+ clean_restart
+
+ gdb_load ${binfile}
+ gdb_load_shlib $binfile_lib
+
+ if ![runto_main] {
+ fail "can't run to main"
+ return 0
+ }
+
+ gdb_test "catch catch" "Catchpoint \[0-9\]+ \\(catch\\)" \
+ "catch catch"
+ gdb_test "catch throw" "Catchpoint \[0-9\]+ \\(throw\\)" \
+ "catch throw"
+ gdb_test "catch rethrow" "Catchpoint \[0-9\]+ \\(rethrow\\)" \
+ "catch rethrow"
+
+ set ws "\[ \t\]*"
+ gdb_test "info breakpoints" \
+ [multi_line \
+ "${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception catch" \
+ "${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception throw" \
+ "${decimal}${ws}breakpoint${ws}keep${ws}y${ws}${hex}${ws}exception rethrow"]
+}
+
+# Try different static/not-static combinations.
+foreach_with_prefix static_lib {"0" "1"} {
+ foreach_with_prefix static_bin {"0" "1"} {
+ test_multi_libstdcpp $static_lib $static_bin
+ }
+}
--
2.14.5