c++ lldb debugger seems hangs #860

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1. pieandcakes commented on Jul 5, 2017

   

   Pierson Lee (pieandcakes)

   on Jul 5, 2017

   Last edited by pieandcakes

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   hai (@haiy) we use MI command interpreter mode in lldb to talk to the debugger. You can duplicate this from the command line by using lldb-mi instead of lldb. To see what we are sending and what we get back, you can enable "logging": { "engineLogging": true }

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2. Pierson Lee (pieandcakes)

   added

   debugger

   on Jul 5, 2017
3. Pierson Lee (pieandcakes)

   added

   more info neededThe issue report is not actionable in its current stateThe issue report is not actionable in its current state

   on Oct 7, 2017
4. pieandcakes commented on Oct 7, 2017

   

   Pierson Lee (pieandcakes)

   on Oct 7, 2017

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   Please provide more information if this is still an issue and reopen.
5. Pierson Lee (pieandcakes)

   closed this as completedon Oct 7, 2017
6. peteralm80 commented on Apr 24, 2018

   

   Peter Alm (peteralm80)

   on Apr 24, 2018

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   I managed to reproduce this in a small project. The uninitialised vectors needed to be in a class with a vtable for them to have garbage data.

   This the engineLogging for the problem with a breakpoint at line 24, lldb-mi seems to get stuck at var-create:

   1: (850) ->*stopped,reason="breakpoint-hit",disp="del",bkptno="2",frame={level="0",addr="0x0000000100001ec6",func="main",args=[],file="lldb-hang.cpp",fullname="/Users/peter/src/lldb-hang/lldb-hang.cpp",line="24"},thread-id="1",stopped-threads="all"   
   1: (850) ->(gdb)
   1: (851) <-1013-thread-info 1
   1: (851) <-1014-thread-info
   1: (851) ->1013^done,threads=[{id="1",target-id="Thread 1",frame={level="0",addr="0x0000000100001ec6",func="main",args=[],file="lldb-hang.cpp",fullname="/Users/peter/src/lldb-hang/lldb-hang.cpp",line="24"},frame={level="1",addr="0x00007fff60c13015",func="start",args=[],file="??",fullname="??",line="-1"},state="stopped"}]
   1: (851) ->(gdb)
   1: (852) 1013: elapsed time 0
   1: (852) ->1014^done,threads=[{id="1",target-id="Thread 1",frame={level="0",addr="0x0000000100001ec6",func="main",args=[],file="lldb-hang.cpp",fullname="/Users/peter/src/lldb-hang/lldb-hang.cpp",line="24"},frame={level="1",addr="0x00007fff60c13015",func="start",args=[],file="??",fullname="??",line="-1"},state="stopped"}],current-thread-id="1"
   1: (852) ->(gdb)
   1: (852) 1014: elapsed time 0
   Execute debugger commands using "-exec <command>", for example "-exec info registers" will list registers in use (when GDB is the debugger)
   1: (888) <-1015-stack-list-variables 0 --thread 1 --frame 0
   1: (891) ->1015^done,variables=[{name="baz"}]
   1: (891) 1015: elapsed time 3
   1: (891) ->(gdb)
   1: (894) <-1016-var-create - - "baz" --thread 1 --frame 0
   

   Running this in the regular lldb-cli you can see that the one of the vectors has a sizeof 2^32-1:

   * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
       frame #0: 0x0000000100001e96 lldb-hang`main at lldb-hang.cpp:24
      21   int main()
      22   {
      23       foo();
   -> 24       std::cout << "Hello world\n";
      25       Foo baz[10];
      26   }
   Target 0: (lldb-hang) stopped.
   (lldb) p baz
   (Foo [10]) $0 = {
     [0] = {
       vec_ = size=0 {}
     }
     [1] = {
       vec_ = size=0 {}
     }
     [2] = {
       vec_ = size=0 {}
     }
     [3] = {
       vec_ = size=0 {}
     }
     [4] = {
       vec_ = size=0 {}
     }
     [5] = {
       vec_ = size=0 {}
     }
     [6] = {
       vec_ = size=0 {}
     }
     [7] = {
       vec_ = size=4294967295 {
         [0] = 72057628379708111
         [1] = 10737418243
         [2] = 7078106103824
   ...
   

   If I attach lldb to the hung lldb-mi process I can see that var-create is stuck iterating over 4 billion entries in this for loop: https://github.com/llvm-mirror/lldb/blob/master/tools/lldb-mi/MICmdCmdVar.cpp#L300

   lldb-hang.zip
7. haohaolee commented on Apr 12, 2020

   

   Hao Li (haohaolee)

   on Apr 12, 2020

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   The same here. lldb-mi hangs at 100% cpu and the last message is:
   -var-create - - "result" --thread 1 --frame 0

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8. zwangz commented on Jul 18, 2020

   

   zwangz

   on Jul 18, 2020

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   The same here. lldb-mi hangs at 100% cpu and the last message is:
   -var-create - - "result" --thread 1 --frame 0

   Same issue here

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