[Lldb-commits] [PATCH] D26093: Limit LLDB_EXPORT_ALL_SYMBOLS to additionally export only the lldb_private namespace symbols
Pavel Labath via lldb-commits
lldb-commits at lists.llvm.org
Mon Oct 31 05:54:48 PDT 2016
labath added a comment.
The snippets you showed are pretty-much expected behavior. The backtrace that gets printed as a part of the log messages is coming from the backtrace(3) library, which has pretty limited backtracing capabilities -- it only looks at the symbols in the `.dynsym` section (because that's the only thing that is loaded into memory). I am pretty sure you would have problems backtracing if you compiled with -fomit-frame-pointer as well.
I think you fix of just making sure that all symbols show up in the .dynsym section would be fine, were it not for that fact that we have an inconsistent linking policy, which means you get wildly different links depending on whether you export something or not. If we get that straight that this would just be a size optimization (that was the reason we introduced it), with no impact on the behavior, that we could even consider turning off by default (I personally have never used the -S option of logging, but I can see how it could be useful in some workflows). I'll get back to the link policy in a separate email.
That said, you mentioned you also had some problems with setting breakpoints and stuff. Now, if this was true, that would be extremely worrying, but am not able to reproduce that on my side -- breakpoints everything else works fine. The reason for that is that lldb reads the .symtab section (if it is present, which it will be unless you strip the executable), and these linker options do not affect that section. If that is not the case, then we definitely need to figure that out (I suggest stepping through ObjectFileELF::GetSymtab() to get an initial idea of what is going on).
FWIW, this is how a debug session looks like for me. The backtrace() output has addresses only, but lldb is able to symbolicate it with no problem:
$ bin/lldb -- bin/lldb /bin/ls
(lldb) target create "bin/lldb"
Current executable set to 'bin/lldb' (x86_64).
(lldb) settings set -- target.run-args "/bin/ls"
(lldb) br set -n Log::VAPrintf
Breakpoint 1: no locations (pending).
WARNING: Unable to resolve breakpoint to any actual locations.
(lldb) pr la
Process 87438 launched: '/usr/local/google/home/labath/ll/build/dbg/bin/lldb' (x86_64)
1 location added to breakpoint 1
Process 87438 stopped and restarted: thread 1 received signal: SIGCHLD
(lldb) target create "/bin/ls"
Current executable set to '/bin/ls' (x86_64).
(lldb) log enable -S lldb process
(lldb) pr la
Process 87438 stopped
* thread #1: tid = 87438, 0x00007ffff0d1cfeb liblldb.so.40`lldb_private::Log::VAPrintf(this=0x000000000059a560, format="ProcessLaunchInfo::%s at least one of stdin/stdout/stderr was not set, evaluating default handling", args=0x00007fffffffc1a0) + 27 at Log.cpp:73, name = 'lldb', stop reason = breakpoint 1.1
frame #0: 0x00007ffff0d1cfeb liblldb.so.40`lldb_private::Log::VAPrintf(this=0x000000000059a560, format="ProcessLaunchInfo::%s at least one of stdin/stdout/stderr was not set, evaluating default handling", args=0x00007fffffffc1a0) + 27 at Log.cpp:73
70 void Log::VAPrintf(const char *format, va_list args) {
71 // Make a copy of our stream shared pointer in case someone disables our
72 // log while we are logging and releases the stream
-> 73 StreamSP stream_sp(m_stream_sp);
74 if (stream_sp) {
75 static uint32_t g_sequence_id = 0;
76 StreamString header;
(lldb) c
Process 87438 resuming
ProcessLaunchInfo::FinalizeFileActions at least one of stdin/stdout/stderr was not set, evaluating default handling
0 liblldb.so.40 0x00007ffff4d5a36f
1 liblldb.so.40 0x00007ffff0d1d49f
2 liblldb.so.40 0x00007ffff0d1cfbb
3 liblldb.so.40 0x00007ffff0fff4c4
4 liblldb.so.40 0x00007ffff103ad63
5 liblldb.so.40 0x00007ffff15c4f9f
6 liblldb.so.40 0x00007ffff0e33fe0
7 liblldb.so.40 0x00007ffff0e20317
8 liblldb.so.40 0x00007ffff0e25c0d
9 liblldb.so.40 0x00007ffff0e265a7
10 liblldb.so.40 0x00007ffff0cf5a60
11 liblldb.so.40 0x00007ffff0cb5c3c
12 liblldb.so.40 0x00007ffff0e26fdf
13 liblldb.so.40 0x00007ffff09d8d21 lldb::SBDebugger::RunCommandInterpreter(bool, bool) + 129
14 lldb 0x0000000000407c15
15 lldb 0x0000000000408257
16 libc.so.6 0x00007fffeeeb8f45 __libc_start_main + 245
17 lldb 0x00000000004038d9
Process 87438 stopped
* thread #1: tid = 87438, 0x00007ffff0d1cfeb liblldb.so.40`lldb_private::Log::VAPrintf(this=0x000000000059a560, format="ProcessLaunchInfo::%s target stdin='%s', target stdout='%s', stderr='%s'", args=0x00007fffffffc1a0) + 27 at Log.cpp:73, name = 'lldb', stop reason = breakpoint 1.1
frame #0: 0x00007ffff0d1cfeb liblldb.so.40`lldb_private::Log::VAPrintf(this=0x000000000059a560, format="ProcessLaunchInfo::%s target stdin='%s', target stdout='%s', stderr='%s'", args=0x00007fffffffc1a0) + 27 at Log.cpp:73
70 void Log::VAPrintf(const char *format, va_list args) {
71 // Make a copy of our stream shared pointer in case someone disables our
72 // log while we are logging and releases the stream
-> 73 StreamSP stream_sp(m_stream_sp);
74 if (stream_sp) {
75 static uint32_t g_sequence_id = 0;
76 StreamString header;
(lldb) bt
* thread #1: tid = 87438, 0x00007ffff0d1cfeb liblldb.so.40`lldb_private::Log::VAPrintf(this=0x000000000059a560, format="ProcessLaunchInfo::%s target stdin='%s', target stdout='%s', stderr='%s'", args=0x00007fffffffc1a0) + 27 at Log.cpp:73, name = 'lldb', stop reason = breakpoint 1.1
* frame #0: 0x00007ffff0d1cfeb liblldb.so.40`lldb_private::Log::VAPrintf(this=0x000000000059a560, format="ProcessLaunchInfo::%s target stdin='%s', target stdout='%s', stderr='%s'", args=0x00007fffffffc1a0) + 27 at Log.cpp:73
frame #1: 0x00007ffff0d1cfbb liblldb.so.40`lldb_private::Log::Printf(this=0x000000000059a560, format="ProcessLaunchInfo::%s target stdin='%s', target stdout='%s', stderr='%s'") + 347 at Log.cpp:61
frame #2: 0x00007ffff0fff970 liblldb.so.40`lldb_private::ProcessLaunchInfo::FinalizeFileActions(this=0x00000000004a0170, target=0x000000000058bea0, default_to_use_pty=true) + 1376 at ProcessLaunchInfo.cpp:260
frame #3: 0x00007ffff103ad63 liblldb.so.40`lldb_private::Target::Launch(this=0x000000000058bea0, launch_info=0x00000000004a0170, stream=0x00007fffffffcaa8) + 1315 at Target.cpp:2835
frame #4: 0x00007ffff15c4f9f liblldb.so.40`CommandObjectProcessLaunch::DoExecute(this=0x00000000004a0030, launch_args=0x00007fffffffcd68, result=0x00007fffffffd4d8) + 1647 at CommandObjectProcess.cpp:233
frame #5: 0x00007ffff0e33fe0 liblldb.so.40`lldb_private::CommandObjectParsed::Execute(this=0x00000000004a0030, args_string="", result=0x00007fffffffd4d8) + 1344 at CommandObject.cpp:1008
frame #6: 0x00007ffff0e20317 liblldb.so.40`lldb_private::CommandInterpreter::HandleCommand(this=0x0000000000482750, command_line="pr la", lazy_add_to_history=eLazyBoolCalculate, result=0x00007fffffffd4d8, override_context=0x0000000000000000, repeat_on_empty_command=true, no_context_switching=false) + 3527 at CommandInterpreter.cpp:1679
frame #7: 0x00007ffff0e25c0d liblldb.so.40`lldb_private::CommandInterpreter::IOHandlerInputComplete(this=0x0000000000482750, io_handler=0x0000000000583190, line="pr la") + 301 at CommandInterpreter.cpp:2713
frame #8: 0x00007ffff0e265a7 liblldb.so.40`non-virtual thunk to lldb_private::CommandInterpreter::IOHandlerInputComplete(this=0x0000000000482750, io_handler=0x0000000000583190, line="pr la") + 55 at CommandInterpreter.cpp:2689
frame #9: 0x00007ffff0cf5a60 liblldb.so.40`lldb_private::IOHandlerEditline::Run(this=0x0000000000583190) + 608 at IOHandler.cpp:552
frame #10: 0x00007ffff0cb5c3c liblldb.so.40`lldb_private::Debugger::ExecuteIOHandlers(this=0x0000000000480e90) + 140 at Debugger.cpp:899
frame #11: 0x00007ffff0e26fdf liblldb.so.40`lldb_private::CommandInterpreter::RunCommandInterpreter(this=0x0000000000482750, auto_handle_events=true, spawn_thread=false, options=0x00007fffffffd7d8) + 223 at CommandInterpreter.cpp:2910
frame #12: 0x00007ffff09d8d21 liblldb.so.40`lldb::SBDebugger::RunCommandInterpreter(this=0x00007fffffffdb48, auto_handle_events=true, spawn_thread=false) + 129 at SBDebugger.cpp:814
frame #13: 0x0000000000407c15 lldb`Driver::MainLoop(this=0x00007fffffffdb28) + 4341 at Driver.cpp:1156
frame #14: 0x0000000000408257 lldb`main(argc=2, argv=0x00007fffffffdd28) + 471 at Driver.cpp:1254
frame #15: 0x00007fffeeeb8f45 libc.so.6`__libc_start_main(main=(lldb`main at Driver.cpp:1218), argc=2, argv=0x00007fffffffdd28, init=<unavailable>, fini=<unavailable>, rtld_fini=<unavailable>, stack_end=0x00007fffffffdd18) + 245 at libc-start.c:287
frame #16: 0x00000000004038d9 lldb`_start + 41
Repository:
rL LLVM
https://reviews.llvm.org/D26093
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