[lldb-dev] Using LLDB to catch a spurious segfault: scripting, etc.

[William Knop]

Brilliant! Between this example and Jim's, I think I'll be able to put
something nice together.

Thank you both,
Will

On Fri, Apr 1, 2011 at 9:26 PM, Johnny Chen <johnny.chen at apple.com> wrote:
> Hi William,
> Wonder if:
> URL: http://llvm.org/viewvc/llvm-project?rev=128755&view=rev
> Log:
> Add a Python script which launches a program from within lldb and loop until
> the
> process stops for some reason.  main.c (compiled into a.out) is used as an
> example in
> the README-run-until-faulted file.
>
> Added:
>    lldb/trunk/utils/test/README-run-until-faulted
>    lldb/trunk/utils/test/main.c
>    lldb/trunk/utils/test/run-until-faulted.py   (with props)
>
> is a good enough start for your need?
> Thanks.
> On Mar 31, 2011, at 6:15 PM, William Knop wrote:
>
> Hello all,
>
> I am attempting to use lldb to debug a segfault in my program that
> happens sporadically. For instance, running `for ((i=0;i<1000;i++)) {
> ./myprogram; };` at a shell prompt may show one. It seems there is no
> way to set lldb to run automatically and exit upon success from the
> CLI, so I've been exploring lldb's python scripting.
>
> The goal of the script is to loop, launching the process until
> completion or error; if there's an error, I need the script to dump me
> back into the lldb interpreter to investigate the bug. Here's what
> I've come up with so far:
>
> import time
>
> dbg = lldb.SBDebugger.FindDebuggerWithID(lldb.debugger_unique_id)
>
> ci = dbg.GetCommandInterpreter()
>
> res = lldb.SBCommandReturnObject()
>
> dbg.SetAsync(False)
>
> for i in range(1, 1000):
>
>  ci.HandleCommand("process launch", res)
>
>  while (not res.Succeeded()) : time.sleep(0.1)
>
>  res.Clear()
>
> Unfortunately, however, it seems the command does not run to
> completion, no matter how long I wait. Then when I call
> `HandleCommand` a second time, lldb deadlocks. I intended to
> eventually check `res.GetError()` or `res.GetStatus()` and call
> `quit()` when the error appeared, but I haven't made it that far. I
> also initially explored calling `dbg.GetTargetAtIndex(0).Launch()`
> rather than `HandleCommand`, but I wasn't entirely sure how to go
> about it. Any help would be much appreciated!
>
> Will
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