[lldb-dev] Debugging a running process with lldb

Matthew Gardiner mg11 at csr.com
Wed May 14 03:22:47 PDT 2014

More thoughts:

I've read http://lldb.llvm.org/tutorial.html in more depth now ;-) 
(appreciating that the debugger and the inferior require separate stdins.)
I see there's an option, "--no-stdin", proposing to mitigate the issue I 

"If you attach to a process, or launch a process with the "|--no-stdin|" 
option, the command interpreter is always available to enter commands. 
This might be a little disconcerting to gdb users when always have an 
|(lldb)| prompt. This allows you to set a breakpoint, etc without having 
to explicitly interrupt the program you are debugging:

|(lldb) process continue
(lldb) breakpoint set --name stop_here |

However, it seems that --no-stdin is not present as a "process launch" 
option anymore, but rather we have "--no-stdio". (Perhaps a typo, 
somewhere?). I tried this option:

(lldb) process launch -s --no-stdio
Process 2344 launching
Process 2344 launched: './forever' (x86_64)
Process 2344 stopped
* thread #1: tid = 2344, 0x0000003675a011f0, name = 'forever', stop 
reason = trace
     frame #0: 0x0000003675a011f0
-> 0x3675a011f0:  movq   %rsp, %rdi
    0x3675a011f3:  callq  0x3675a046e0
    0x3675a011f8:  movq   %rax, %r12
    0x3675a011fb:  movl   0x21eb97(%rip), %eax
(lldb) process continue
Process 2344 resuming

The interpreter prompt still fails to appear, so I still think I'm 
either seeing a bug, or that the documentation is incomplete as to 
describing how to run lldb such that the command interpreter, is always 
available when the inferior is running.


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