Debugging problems with MacPorts GCC on OS X - c++

Question

I can't seem to get readable debugging output for programs compiled with GCC 4.7 MacPorts build.
I've tried with both GDB 6.3 and GDB 7.3 and each have their own problems.
Try with GDB 7.3 (MacPorts)
With GDB 7.3 I get the following output on startup:
$ ggdb ./test
GNU gdb (GDB) 7.3
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin11.4.0".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
BFD: unable to read unknown load command 0x24
BFD: unable to read unknown load command 0x26
BFD: unable to read unknown load command 0x24
BFD: unable to read unknown load command 0x26
Reading symbols from /Users/StackedCrooked/programming/projects/stacked-crooked/Playground/LockOrderChecker/test...Reading symbols from /Users/StackedCrooked/programming/projects/stacked-crooked/Playground/LockOrderChecker/test.dSYM/Contents/Resources/DWARF/test...done.
done.
Running and triggering an assertion results in an unreadable stack trace:
(gdb) r
Starting program: /Users/StackedCrooked/programming/projects/stacked-crooked/Playground/LockOrderChecker/test
BFD: unable to read unknown load command 0x24
BFD: unable to read unknown load command 0x26
main
Assertion failed: (false), function lock, file main.cpp, line 168.
Program received signal SIGABRT, Aborted.
0x00007fff8ede282a in ?? ()
(gdb) bt
#0 0x00007fff8ede282a in ?? ()
#1 0x00007fff9a273a9c in ?? ()
#2 0x00007fff6af00690 in ?? ()
#3 0x0000003000000030 in ?? ()
#4 0x00007fffffffffdf in ?? ()
#5 0x000000010b305840 in ?? ()
#6 0x00007fff6af006d0 in ?? ()
#7 0x00007fff9a2a65de in ?? ()
#8 0x0000000000000000 in ?? ()
Try with GDB 6.3 (built-in)
According to this answer I should use GDB 6.3. However that leads to a different set of problems. During startup I get a bunch of errors:
GNU gdb 6.3.50-20050815 (Apple version gdb-1708) (Thu Nov 3 21:59:02 UTC 2011)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin"...Reading symbols for shared libraries .
warning: Could not find object file "/Volumes/work/macports/var/macports/build/_Volumes_work_mports_dports_lang_gcc47/gcc47/work/build/x86_64-apple-darwin11/libstdc++-v3/src/.libs/compatibility.o" - no debug information available for "../../../../gcc-4.7.1/libstdc++-v3/src/c++98/compatibility.cc".
warning: Could not find object file "/Volumes/work/macports/var/macports/build/_Volumes_work_mports_dports_lang_gcc47/gcc47/work/build/x86_64-apple-darwin11/libstdc++-v3/src/.libs/compatibility-debug_list.o" - no debug information available for "../../../../gcc-4.7.1/libstdc++-v3/src/c++98/compatibility-debug_list.cc".
warning: Could not find object file "/Volumes/work/macports/var/macports/build/_Volumes_work_mports_dports_lang_gcc47/gcc47/work/build/x86_64-apple-darwin11/libstdc++-v3/src/.libs/compatibility-debug_list-2.o" - no debug information available for "../../../../gcc-4.7.1/libstdc++-v3/src/c++98/compatibility-debug_list-2.cc".
This is what I see if an assertion is triggered and I try to get a backtrace:
Assertion failed: (false), function lock, file main.cpp, line 168.
Program received signal SIGABRT, Aborted.
0x00007fff8ede282a in __kill ()
(gdb) bt
#0 0x00007fff8ede282a in __kill ()
#1 0x00007fff9a273a9c in abort ()
#2 0x00007fff9a2a65de in __assert_rtn ()
Die: DW_TAG_unspecified_type (abbrev = 19, offset = 423)
has children: FALSE
attributes:
DW_AT_name (DW_FORM_strp) string: "decltype(nullptr)"
Die: DW_TAG_unspecified_type (abbrev = 19, offset = 423)
has children: FALSE
attributes:
DW_AT_name (DW_FORM_strp) string: "decltype(nullptr)"
Dwarf Error: Cannot find type of die [in module /Users/StackedCrooked/programming/projects/stacked-crooked/Playground/LockOrderChecker/test.dSYM/Contents/Resources/DWARF/test]
According to this answer (which quotes the GCC 4.5 manual) I should use the -gdwarf-2 -gstrict-dwarf options.
I followed this advice. My build command looks like this:
g++ -o run-test -std=c++0x -Wall -Wextra -Werror -gdwarf-2 -gstrict-dwarf -g2 -O0 -I/opt/local/include main.cpp
However, it doesn't fix any of the aforementioned problems.
For the record: I'm on OS X Lion.
Does anyone know how to fix this?

Answer 1

According to the g++ man pages you should use -ggdb to generate debug symbols for gdb. BTW, just using -g always generated good symbols for gdb in my experience (on linux, windows (mingw) and mac).

Answer 2

The warnings from your MacPorts gdb 7.3 session are for load commands 0x24 (LC_VERSION_MIN_MACOSX) and 0x26 (LC_FUNCTION_STARTS). These are new load commands but are not essential for debugging - the warnings are harmless. The fact that your session lacks any symbolic information is maybe because of ASLR? It's been years since that was introduced into the system for user land debugging but that's what the debugger output can look like if it doesn't know that everything slid around in memory at runtime.
Have you tried using lldb? The version provided in Xcode 4.5 is really quite nice. It is the debugger that Apple is currently supporting and developing actively, and it should work with the DWARF output by more recent compilers correctly. The command syntax is a little different than gdb (although there are many command shortcuts provided that make it familiar to gdb users), there's a table of gdb/lldb command equivalences provided over at http://lldb.llvm.org/lldb-gdb.html. Give it a try, you might like it.