Fix "info break" + "catch catch" + -static-{libstdc++,libgcc}

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:
2019-07-09  Pedro Alves  <palves@redhat.com>

	PR c++/15468
	* breakpoint.c (print_one_breakpoint_location): Remove
	single-location assert.

gdb/testsuite/ChangeLog:
2019-07-09  Pedro Alves  <palves@redhat.com>

	PR c++/15468
	* gdb.cp/except-multi-location-lib.cc: New.
	* gdb.cp/except-multi-location-main.cc: New.
	* gdb.cp/except-multi-location.exp: New.
This commit is contained in:
Pedro Alves 2019-07-09 19:26:15 +01:00
parent 0826779b99
commit b58a68fe57
6 changed files with 162 additions and 7 deletions

View File

@ -1,3 +1,9 @@
2019-07-09 Pedro Alves <palves@redhat.com>
PR c++/15468
* breakpoint.c (print_one_breakpoint_location): Remove
single-location assert.
2019-07-09 Tom Tromey <tom@tromey.com> 2019-07-09 Tom Tromey <tom@tromey.com>
* contrib/ari/gdb_ari.sh: Change common to gdbsupport. * contrib/ari/gdb_ari.sh: Change common to gdbsupport.

View File

@ -6033,13 +6033,7 @@ print_one_breakpoint_location (struct breakpoint *b,
/* 5 and 6 */ /* 5 and 6 */
if (b->ops != NULL && b->ops->print_one != NULL) if (b->ops != NULL && b->ops->print_one != NULL)
{ b->ops->print_one (b, last_loc);
/* 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);
}
else else
switch (b->type) switch (b->type)
{ {

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@ -1,3 +1,10 @@
2019-07-09 Pedro Alves <palves@redhat.com>
PR c++/15468
* gdb.cp/except-multi-location-lib.cc: New.
* gdb.cp/except-multi-location-main.cc: New.
* gdb.cp/except-multi-location.exp: New.
2019-07-09 Sergio Durigan Junior <sergiodj@redhat.com> 2019-07-09 Sergio Durigan Junior <sergiodj@redhat.com>
* gdb.base/printcmds.exp (test_printf_convenience_var): Set * gdb.base/printcmds.exp (test_printf_convenience_var): Set

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@ -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 (...)
{
}
}

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@ -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;
}

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@ -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
}
}