[lldb-dev] [Bug 23745] New: On FreeBSD, debugger not entered on explicit debugger trap

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=23745

            Bug ID: 23745
           Summary: On FreeBSD, debugger not entered on explicit debugger
                    trap
           Product: lldb
           Version: unspecified
          Hardware: PC
                OS: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: lldb-dev at cs.uiuc.edu
          Reporter: emaste at freebsd.org
    Classification: Unclassified

In debug mode Chromium calls an explicit debugger trap on fatal conditions. In
gdb this looks like:

feynman% gdb79 work/stage/usr/local/share/chromium/chrome
...
(gdb) run
Starting program:
/tank/emaste/src/ports/www/chromium/work/stage/usr/local/share/chromium/chrome 
...
Program received signal SIGTRAP, Trace/breakpoint trap.
[Switching to Thread 81f406400 (LWP 101775)]
base::debug::(anonymous namespace)::DebugBreak () at
../../base/debug/debugger_posix.cc:228

and I can 'c'ontinue from there.

In LLDB:

% ... bin/lldb work/stage/usr/local/share/chromium/chrome

(lldb) run
Process 72518 launching
** some time later
Process 72518 launched:
'/tank/emaste/src/ports/www/chromium/work/stage/usr/local/share/chromium/chrome'
(x86_64)
** ... then debug output from Chromium:
[72518:524313600:0603/133227:WARNING:internal_linux.cc(58)] Failed to read
/proc/72518/stat
[72518:524313600:0603/133227:FATAL:process_info_linux.cc(20)] Check failed:
start_ticks. 
#0 0x00000187b85e <unknown>
#1 0x0000018c5d66 <unknown>
#2 0x000001917964 <unknown>
#3 0x000005f1d1b0 <unknown>

Then it remains idle, until I press ^C

^C
Process 72518 stopped
(lldb) bt
* thread #18: tid = 103217, 0x000000081bcc14ba libc.so.7`__sys_poll + 10 at
_poll.S:3
  * frame #0: 0x000000081bcc14ba libc.so.7`__sys_poll + 10 at _poll.S:3
    frame #1: 0x0000000819c79d26 libthr.so.3`__thr_poll(fds=<unavailable>,
nfds=<unavailable>, timeout=<unavailable>) + 54 at thr_syscalls.c:318
    frame #2: 0x000000081099c300 libglib-2.0.so.0`??? + 432
    frame #3: 0x000000081099c65f libglib-2.0.so.0`g_main_loop_run + 207
    frame #4: 0x00000008148946eb libgio-2.0.so.0`??? + 27
    frame #5: 0x00000008109c202a libglib-2.0.so.0`??? + 90
    frame #6: 0x0000000819c777c5
libthr.so.3`thread_start(curthread=0x000000081f411800) + 277 at
thr_create.c:288

And then after resuming the expected debugger trap is received:

(lldb) c
Process 72518 resuming
Process 72518 stopped
* thread #1: tid = 104448, 0x000000000187a906 chrome`base::debug::(anonymous
namespace)::DebugBreak() + 22 at debugger_posix.cc:220, stop reason = signal
SIGSTOP
    frame #0: 0x000000000187a906 chrome`base::debug::(anonymous
namespace)::DebugBreak() + 22 at debugger_posix.cc:220
   217      abort();
   218    } else {
   219  #if defined(DEBUG_BREAK_ASM)
-> 220      DEBUG_BREAK_ASM();
   221  #else
   222      volatile int go = 0;
   223      while (!go) {
(lldb)

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