bug#57849: 29.0.50; MacOS ld warning from native compilation

[Gerd Möllmann]

Eli Zaretskii <eliz@gnu.org> writes:

> Is this somehow an Emacs-specific problem, or is this a general
> problem with libgccjit on those versions of macOS?

I think it's a general problem with macOS 12.6/Xcode 14, but I'm not sure.
The link Gregory and/or Lars posted concerned Ruvy, IIRC.

> If the latter, I
> think this should be taken up with the libgccjit developers first, and
> we should then do as they say, if that makes sense.

Maybe Andrea can say more.  I don't know libgccjit and the native
compiler well enough.

>> Otherwise my proposal is to
>> either add something to etc/PROBLEMS describing how to add "-Wl,-w", or
>> add that option by default on Darwin.
>
> If what the libgccjit developers say doesn't fit our needs, or if this
> is an Emacs-specific problem, thgen yes, using -Wl,-w is probably the
> way to go.
>
>> I didn't check if emacs-28 has the same problem, but I don't see why it
>> wouldn't.
>
> It's okay to make that change on the emacs-28 branch, if someone can
> verify that it works on that branch.

I've tried this in emacs-28, which seems to work, with a caveat

@@ -178,14 +178,15 @@ native-comp-compiler-options
   :type '(repeat string)
   :version "28.1")
 
-(defcustom native-comp-driver-options nil
+(defcustom native-comp-driver-options (when (eq system-type 'darwin)
+                                        '("-Wl,-w"))
   "Options passed verbatim to the native compiler's back-end driver.
 Note that not all options are meaningful; typically only the options
 affecting the assembler and linker are likely to be useful.
 
 Passing these options is only available in libgccjit version 9
 and above."
-  :type '(repeat string)                ; FIXME is this right?
+  :type '(repeat string)
   :version "28.1")
 
 (defcustom comp-libgccjit-reproducer nil

The caveat being that I see, after starting that Emacs, in the log
buffer

uncompressing time-date.el.gz...done
ld: library not found for -lemutls_w
libgccjit.so: error: error invoking gcc driver
/Users/gerd/emacs/emacs-28/nextstep/Emacs.app/Contents/Resources/lisp/emacs-lisp/comp.el.gz:
 Error: Internal native compiler error failed to compile

The build was from git clean -xdf.  Don't know what's going on there.
Maybe it's not related to my change.  I'll try without the change later
today.

>
>> If we add -Wl by default, an open question is if -w is supported on all
>> all versions of MacOS that Emacs supports, which I can't find a definite
>> answer to.
>
> I think -w is such an old option that it'd be unthinkable for it not
> to be supported.

That's likely, yes.