Re: [PATCH 2/3] gdb/symtab: add lookup for trampoline functions

[Tom Tromey <tom@tromey.com>]

>>>>> Nils-Christian Kempke via Gdb-patches <gdb-patches@sourceware.org> writes:

> In order to queriy information about the DW_AT_trampoline tag for
> subroutines and inlined subroutines two function were added to symtab.

> First, a routine for querying whether the given pc belongs to a block
> that is associated with a function (maybe inlined) marked
> DW_AT_trampoline.

> Second, a routine for querying a trampoline function's target.
> Subroutines and inlined subroutines marked with DW_AT_trampoline usually
> contain information about the target subroutine they are 'wrapping'/
> passing control to.

Thank you for the patch.

> gdb/ChangeLog:
> 2022-05-30  Nils-Christian Kempke  <nils-christian.kempke@intel.com>

> 	* symtab.h (in_trampoline_function): New function
> 	(find_function_trampoline_target): New function.
> 	* symtab.c (in_trampoline_function): New function implementation.
> 	(find_function_trampoline_target): New implementation of
> 	trampoline target lookup.

These aren't needed any more.

> +      if (trampoline->target_kind () == TRAMPOLINE_TARGET_PHYSNAME)
> +	{
> +	  /* Handle both the mangled and demangled PHYSNAME.  */
> +	  const char *physname = trampoline->target_physname ();
> +
> +	  if (find_minimal_symbol_address (physname, &target_address, nullptr)
> +	      != 0)
> +	    target_address = 0;

Will there always be a minimal symbol?  It seems like maybe this isn't a
requirement.

> +	  /* If the function symbol containing this trampoline target has
> +	     been relocated we assume the target_address also needs relocation.
> +	     If it has not been relocated the offset should be zero.  */
> +	  target_address = trampoline->target_physaddr ()
> +	    + sym->objfile ()->section_offsets[sym->section_index ()];

It seems to me that this adds an additional section offset, even though
one was already added when reading.

However as mentioned there, it's better to do this work here and undo
the offset in the reader.

Also this isn't formatted properly, you need parens around the right
hand side of the assignment.

Tom