Debug info on macOS

[Gerd Möllmann]

On 2024-05-11 05:39, Gerd Möllmann wrote:
> David Malcolm <dmalcolm@redhat.com> writes:
> 
>> As I understand it, Emacs is using libgccjit to do ahead-of-time
>> compilation, presumably compiling the optimized ELisp code to machine
>> code as a shared library.
> 
> Correct.
> 
>> Is Emacs using gcc_jit_context_compile_to_file with
>> GCC_JIT_OUTPUT_KIND_DYNAMIC_LIBRARY, or is it doing something more
>> complicated?
> 
> Yes. (Sorry, I forgot to CC Andrea; he sent me here :-)).
> 
>> If that's what it's doing, you might want to take a look
>> at playback::context::compile in gcc/jit-playback.cc (and try stepping
>> through it in the debugger).  In particular, the
>> playback::compile_to_file::postprocess implementation of the
>> playback::context::postprocess vfunc is responsible for taking a .s in
>> a tempdir and turning it into the desired output.  Perhaps there's some
>> macOS-specific special-casing needed there?
>>
>> You might also find it useful to look at the overview of how
>> libgccjit's internals here:
>> https://gcc.gnu.org/onlinedocs/jit/internals/index.html#overview-of-code-structure
>>
>> Hope this is helpful
> 
> Yes it is. Thanks, David!

Found something out.

Passing -save-temps=obj to libgccjit makes it keep the .o file used to 
compile the .eln dylibs in Emacs/macOS. Libgccjit then performs the same 
way gcc-14 does on macOS when compiling with -g.

Maybe one could check what gcc-14 does for -g on macOS, and do the same 
when libgccjit compiles with debug > 0. I'm not familiar enough with GCC 
to do that in a reasoanble time, sorry. And I can't build it easily.