[Bug bootstrap/107059] [13 regression] bootstrap failure after r13-2887-gb04208895fed34

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107059

--- Comment #26 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Tobias Burnus from comment #23)
> Regarding the $BUILD/gcc/include-fixed and xgcc -B $BUILD/gcc:
> 
> In gcc.cc's driver_handle_option:
> 
>         add_prefix (&include_prefixes, arg, NULL,
>                     PREFIX_PRIORITY_B_OPT, 0, 0);
> Adds "$BUILD/gcc/" to the prefix list in include_prefix.plist (priority =
> PREFIX_PRIORITY_B_OPT, require_machine_suffix = os_multilib = 0)
> the include_prefixes.name is "include".
> 
> This is later processed in do_spec_1 as:
>               info.option = "-isystem";
>               info.append = "include";
> ...
>               for_each_path (&include_prefixes, false, info.append_len,
>                              spec_path, &info);
> ...
>               info.append = "include-fixed";
>               for_each_path (&include_prefixes, false, info.append_len,
>                              spec_path, &info);
> which in turn runs with (<prefix> = "$BUILD/gcc/"):
>   
>   <prefix>/x86_64-pc-linux-gnu/13.0.0/
>   <prefix>/x86_64-linux-gnu/
>   <prefix>
> 
> It also sets -iprefix $BUILD/gcc/../lib/gcc/x86_64-pc-linux-gnu/13.0.0/
>              -isystem $BUILD/gcc/{include,include-fixed}

Well, the upper directories to include/include-fixed should stay as they are,
that is how to find the include-fixed directory.
But for multi-arch we need to search both include-fixed/<multiarch_dir>
and include-fixed, so I think we need in addition to the comment 14 patch
also (completely untested):
--- gcc/gcc.cc  2022-09-23 09:02:56.809314447 +0200
+++ gcc/gcc.cc  2022-09-28 21:02:29.751933657 +0200
@@ -6400,6 +6400,18 @@ do_spec_1 (const char *spec, int inswitc
              if (*sysroot_hdrs_suffix_spec)
                info.append = concat (info.append, dir_separator_str,
                                      multilib_dir, NULL);
+             else if (multiarch_dir)
+               {
+                 /* For multiarch, search include-fixed/<multiarch-dir>
+                    before include-fixed.  */
+                 info.append = concat (info.append, dir_separator_str,
+                                       multiarch_dir, NULL);
+                 info.append_len = strlen (info.append);
+                 for_each_path (&include_prefixes, false, info.append_len,
+                                spec_path, &info);
+
+                 info.append = "include-fixed";
+               }
              info.append_len = strlen (info.append);
              for_each_path (&include_prefixes, false, info.append_len,
                             spec_path, &info);
It is roughly what the comment 14 patch does, just in a different spot.