[Lldb-commits] [lldb] [lldb] add stop-at-main option to process launch (PR #67019)

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=?utf-8?q?José?= L. Junior <jljuniorpb at gmail.com>,
=?utf-8?q?José?= L. Junior <jljuniorpb at gmail.com>,
=?utf-8?q?José?= L. Junior <jljuniorpb at gmail.com>
Message-ID:
In-Reply-To: <llvm/llvm-project/pull/67019/lldb at github.com>


jimingham wrote:

Yes that's right.  Normally what happens in program execution is the main executable gets loaded along with the dynamic loader, and then the loader runs, leading the program through several rounds of shared library loading (that can be a lot of shared libraries these days) and THEN runs the user entry point.  Adding this filter means that we won't try to resolve a "main" breakpoint in every one of those shared libraries.

Jim

> On Sep 26, 2023, at 7:39 AM, José Lira Junior ***@***.***> wrote:
> 
> 
> @junior-jl commented on this pull request.
> 
> In lldb/source/Commands/CommandOptionsProcessLaunch.cpp <https://github.com/llvm/llvm-project/pull/67019#discussion_r1337326182>:
> 
> > @@ -38,7 +38,18 @@ Status CommandOptionsProcessLaunch::SetOptionValue(
>    case 's': // Stop at program entry point
>      launch_info.GetFlags().Set(eLaunchFlagStopAtEntry);
>      break;
> -
> +  case 'm': // Stop at main function
> +  {
> +    TargetSP target_sp =
> +        execution_context ? execution_context->GetTargetSP() : TargetSP();
> +    BreakpointSP bp_sp = target_sp->CreateBreakpoint(
> +        nullptr, nullptr, "main", eFunctionNameTypeAuto, eLanguageTypeUnknown,
> It's also a good idea to add a shared library filter instead of the first nullptr in the code above, and specify the main executable. You know the entry point has to be in the main executable, and so it would be inefficient to search the whole world for this breakpoint. It could also end up not being what you want, because some other shared library might call a function named "main" as part of it's shared library loading code (which happens before the language's entry point) so you would in fact stop too early.
> 
> I see. Something like this?
> 
> ModuleSP main_module_sp = target_sp->GetExecutableModule();
> FileSpecList shared_lib_filter;
> shared_lib_filter.Append(main_module_sp->GetFileSpec());
> BreakpointSP bp_sp = target_sp->CreateBreakpoint(
>     &shared_lib_filter, nullptr, "main", eFunctionNameTypeFull, eLanguageTypeUnknown,
>     0, eLazyBoolNo, false, false);
> —
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https://github.com/llvm/llvm-project/pull/67019