[Lldb-commits] [PATCH] D100206: [lldb] [llgs client] Support minimal fork/vfork handling

[Michał Górny via Phabricator via lldb-commits]

mgorny added a comment.

@labath, now's a curious problem I've seen very rarely (I mean, 1 out of 150 attempts or so):

   1: (lldb) command source -s 0 '/home/mgorny/git/llvm-project/build.gentoo/tools/lldb/test/Shell/lit-lldb-init' 
   2: Executing commands in '/home/mgorny/git/llvm-project/build.gentoo/tools/lldb/test/Shell/lit-lldb-init'. 
   3: (lldb) # LLDB init file for the LIT tests. 
   4: (lldb) settings set symbols.enable-external-lookup false 
   5: (lldb) settings set plugin.process.gdb-remote.packet-timeout 60 
   6: (lldb) settings set interpreter.echo-comment-commands false 
   7: (lldb) settings set symbols.clang-modules-cache-path "/home/mgorny/git/llvm-project/build.gentoo/lldb-test-build.noindex/module-cache-lldb" 
   8: (lldb) settings set target.auto-apply-fixits false 
   9: (lldb) settings set target.inherit-tcc true 
  10: (lldb) settings set target.detach-on-error false 
  11: (lldb) target create "/home/mgorny/git/llvm-project/build.gentoo/tools/lldb/test/Shell/Subprocess/Output/vfork-follow-parent-wp.test.tmp" 
  12: Current executable set to '/home/mgorny/git/llvm-project/build.gentoo/tools/lldb/test/Shell/Subprocess/Output/vfork-follow-parent-wp.test.tmp' (x86_64). 
  13: (lldb) command source -s 0 '/home/mgorny/git/llvm-project/lldb/test/Shell/Subprocess/vfork-follow-parent-wp.test' 
  14: Executing commands in '/home/mgorny/git/llvm-project/lldb/test/Shell/Subprocess/vfork-follow-parent-wp.test'. 
  15: (lldb) process launch -s 
  16: Process 240829 launched: '/home/mgorny/git/llvm-project/build.gentoo/tools/lldb/test/Shell/Subprocess/Output/vfork-follow-parent-wp.test.tmp' (x86_64) 
  17: (lldb) watchpoint set variable -w write g_val 
  18: Watchpoint created: Watchpoint 1: addr = 0x00404054 size = 4 state = enabled type = w 
  19:  watchpoint spec = 'g_val' 
  20:  new value: 0 
  21: (lldb) continue 
  22: Process 240829 resuming 
  23: Process 240829 stopped 
  24: * thread #1, name = 'vfork-follow-pa', stop reason = signal SIGSTKFLT 
  25:  frame #0: 0x00007ffff7b3b708 libc.so.6`__vfork + 8 
  26: libc.so.6`__vfork: 
  27: -> 0x7ffff7b3b708 <+8>: pushq %rdi 
  28:  0x7ffff7b3b709 <+9>: cmpl $0xfffff001, %eax ; imm = 0xFFFFF001  
  29:  0x7ffff7b3b70e <+14>: jae 0x7ffff7b3b711 ; <+17> 
  30:  0x7ffff7b3b710 <+16>: retq 

i.e. `vfork()` emits `SIGSTKFLT` for some reason and this confuses the test. I have no clue why this happens — `signal(7)` says that this signal is unused. It might be a bug in glibc, or in glibc-2.33 more specifically.


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  https://reviews.llvm.org/D100206/new/

https://reviews.llvm.org/D100206