c++ lldb debugger seems hangs

[haiy]

• VSCode Version: Code 1.13.1 (379d2efb5539b09112c793d3d9a413017d736f89, 2017-06-14T18:13:05.928Z)
• OS Version: Darwin x64 15.6.0
• Extensions:

Extension	Author	Version
python	donjayamanne	0.6.5
vscode-clang	mitaki28	0.2.2
cpptools	ms-vscode	0.12.0

---

Steps to Reproduce:

1. I'm debugging tensorflow source code,at first I use bazel command

bazel run  -c opt -c dbg --strip=never //tensorflow/cc/example:example 

to compile the source normally and then I use vs to debug.My launch.json is

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(lldb) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceRoot}/bazel-out/darwin_x86_64-dbg/bin/tensorflow/cc/example/example",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceRoot}",
            "environment": [],
            "externalConsole": true,
            "MIMode": "lldb"
        }
    ]
}

at first, the debugger works fine, but when I set a breakpoint at 405 in tensorflow/core/common_runtime/direct_session.cc ,the debugger seems hangs, I can't run to next line or step out.

I've tried to debug the program with lldb in terminal with command

lldb bazel-out/darwin_x86_64-dbg/bin/tensorflow/cc/example/example

everything works normally.

[pieandcakes]

@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 }

[pieandcakes]

Please provide more information if this is still an issue and reopen.

[peteralm80]

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

[haohaolee]

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

[zwangz]

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

Same issue here