[lldb-dev] Stopping "stop reason = exec"

[Chris Lattner via lldb-dev]

That works, thanks Jim!  Agreed that it is ugly though :-)

-Chris

> On Dec 4, 2017, at 6:18 PM, Jim Ingham <jingham at apple.com> wrote:
> 
> Yup, apparently debugserver tells us the stop is for exec directly so we don't treat it as a breakpoint hit.  That sorta makes sense, you don't want to trigger a breakpoint hit every time you find a thread at the pc of a breakpoint (might be a thread that hit a breakpoint, then didn't get to run till the next stop.)  But it defeats the obvious method.
> 
> Anyway, it is a program stop, so you can use a stop hook:
> 
> (lldb) target stop-hook add -n _dyld_start -o continue
> 
> That one does work, though the stop-hook output is a little ugly.  It would also be nice to specify stop-hooks by stop reason too.  But this method does work...
> 
> Jim
> 
> 
>> On Dec 4, 2017, at 4:36 PM, Chris Lattner <sabre at nondot.org> wrote:
>> 
>>> On Dec 4, 2017, at 4:25 PM, Chris Lattner <sabre at nondot.org> wrote:
>>>> For macOS, you can also just do:
>>>> 
>>>> (lldb) break set -n _dyld_start --skip-prologue 0 -s dyld
>>>> Breakpoint 2: where = dyld`_dyld_start, address = 0x000000010000b19c
>>>> (lldb) b com add -o continue
>>>> either in your .lldbinit or in your debug session.  
>>> 
>>> This doesn’t appear to work, I tried both lldb and in a debug session.  I’m starting lldb with “lldb -- swiftc … “ if that matters.
>>> 
>>> (lldb) break set -n _dyld_start --skip-prologue 0 -s dyld
>>> Breakpoint 1: where = dyld`_dyld_start, address = 0x0000000000001000
>>> (lldb) b com add -o continue
>>> Breakpoint 2: no locations (pending).
>>> WARNING:  Unable to resolve breakpoint to any actual locations.
>> 
>> I realize that this is probably because you’re not using the standard ‘b’ alias.  When I use ‘br’, the command succeeds, but I still stop on launch:
>> 
>> (lldb) br com add -o continue
>> (lldb) r
>> There is a running process, kill it and restart?: [Y/n] y
>> Process 24049 exited with status = 9 (0x00000009) 
>> Process 24054 launched: '/Users/clattner/Projects/build/Xcode-ReleaseAssert+swift-DebugAssert/swift-macosx-x86_64/Debug/bin/swiftc' (x86_64)
>> Process 24054 stopped
>> * thread #2, stop reason = exec
>>    frame #0: 0x0000000109852000 dyld`_dyld_start
>> dyld`_dyld_start:
>> ->  0x109852000 <+0>: popq   %rdi
>>    0x109852001 <+1>: pushq  $0x0
>>    0x109852003 <+3>: movq   %rsp, %rbp
>>    0x109852006 <+6>: andq   $-0x10, %rsp
>> Target 0: (swiftc) stopped.
>> 
>> 
>> Thank you for the help, I appreciate it!
>> 
>> -Chris
>> 
>