[lldb-dev] Questions for module/symbol load/unload events

[Jeffrey Tan via lldb-dev]

This is very useful, thanks for the info!

On Mon, Feb 29, 2016 at 10:36 AM, Jim Ingham <jingham at apple.com> wrote:

>
> On Feb 27, 2016, at 8:34 PM, Jeffrey Tan via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
>
> Hi,
>
> I am trying to listen for module/symbol load/unload events and display
> them in output UI so that debugger users can have a basic clue what is
> debugger busy doing while launching a big executable linking many shared
> libraries.
>
> Questions:
> 1. I did not find an API to get current load/unload module during module
> events. I was expecting some static API like lldb.SBModule(or
> SBTarget).GetModuleFromEvent(SBEvent), but this does not exists. I tried to
> treat current PC's module as loading module in module load/unload events.
> But that does not work too(I think because process is not stopped in module
> load/unload events). Do I miss something here?
>
>
> From SBTarget.h:
>
>     static uint32_t
>     GetNumModulesFromEvent (const lldb::SBEvent &event);
>
>     static lldb::SBModule
>     GetModuleAtIndexFromEvent (const uint32_t idx, const lldb::SBEvent
> &event);
>
> Note, you can also cause the process to stop with modules are loaded with
> the setting:
>
> target.process.stop-on-sharedlibrary-events
>
> if that is more convenient for you.
>
>
> 2. Even though "image list" shows I have around 42 modules loaded in
> process, I only got two module load events. Why is that?
>
>
> On OS X the loader loads the closure of modules for whatever it is
> loading, and only stops and informs the debugger when this is all done.  So
> it is quite usual to see only a few load events even though many modules
> get loaded.
>
>
>
> 3. Even though I added lldb.SBTarget.eBroadcastBitSymbolsLoaded, there is
> no event of type eBroadcastBitSymbolsLoaded generated. Is it expected?
> Apparently I have the symbols next to the binary.
>
>
> That event gets sent when symbols are added to an already loaded module.
> It is so a UI will know to refresh the backtrace, local variables, source
> view, etc when code goes from having no symbols to having some symbols.
> Those actions are not needed if the library & its symbols get loaded
> simultaneously, so it isn’t sent in that case.
>
> Jim
>
>
>
> This is tested on mac OSX lldb.
>
> Jeffrey
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>
>
>
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