binutils-gdb/gdb/testsuite/gdb.cp/except-multi-location-main.cc

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/* Copyright 2019-2021 Free Software Foundation, Inc.
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.
2019-07-10 02:26:15 +08:00
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;
}