[Lldb-commits] [lldb] [lldb][DynamicLoader] Fix lldb unable to stop at _dl_debug_state if user set it before the process launched. (PR #88792)

[Jason Molenda via lldb-commits]

jasonmolenda wrote:

Skimming DynamicLoaderPOSIXDYLD (as it is written today), it looks like attach/launch call `SetRendezvousBreakpoint()` which (1) loads ld.so into lldb if it isn't already there, and (2) sets the breakpoint to be notified about future binaries loading.  It loads ld.so via `LoadInterpreterModule` which Finds It somehow (I stopped reading), adds it to the Target, and sets the section load addresses, returns the module_sp.  Then it sets breakpoints on a half dozen notification function names in the ld.so Module.  This is all special-cased for ld.so, and we do not evaluate user breakpoints because we didn't call `Target::ModulesDidLoad` for ld.so.

The code path for other binaries goes through `DynamicLoaderPOSIXDYLD::RefreshModules` which does the normal approach of adding binaries to the Target, setting the load addresses, then calling ModulesDidLoad which will evaluate breakpoints that may need to be set in the new binaries.

It seems like a simpler fix would be to have `DynamicLoaderPOSIXDYLD::LoadInterpreterModule` create a ModuleList with the ModuleSP of ld.so that it has just added to Target and set its section load addresses, then call `ModulesDidLoad` on it so that user breakpoints are evaluated and inserted.  The patch as it is written right now is taking one part of ModulesDidLoad and putting it in a separate method that `DynamicLoaderPOSIXDYLD::LoadInterpreterModule` is calling -- why not just call ModulesDidLoad and delegate this (and possibly other binary-just-loaded) behaviors to it?

https://github.com/llvm/llvm-project/pull/88792