gcc: Resolve relative prefix-map filenames

Add a patch to gcc so that relative paths are handled by -fdebug-prefix-map
and friends. In OE we use relative paths in autotools and removing that
creates a lot of issues we'd have to fix. This alternative allows us to
fix the paths within gcc and improve our debug file coverage (and SPDX
manifests) accordingly.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 63 insertions, 0 deletions

diff --git a/meta/recipes-devtools/gcc/gcc-12.1.inc b/meta/recipes-devtools/gcc/gcc-12.1.inc
index 56678c78be..c42fa3d72f 100644
--- a/meta/recipes-devtools/gcc/gcc-12.1.inc
+++ b/meta/recipes-devtools/gcc/gcc-12.1.inc
@@ -65,6 +65,7 @@ SRC_URI = "${BASEURI} \
            file://0025-Move-sched.h-include-ahead-of-user-headers.patch \
            file://0026-rust-recursion-limit.patch \
            file://0001-libsanitizer-cherry-pick-9cf13067cb5088626ba7-from-u.patch \
+           file://prefix-map-realpath.patch \
 "
 SRC_URI[sha256sum] = "62fd634889f31c02b64af2c468f064b47ad1ca78411c45abe6ac4b5f8dd19c7b"
 
diff --git a/meta/recipes-devtools/gcc/gcc/prefix-map-realpath.patch b/meta/recipes-devtools/gcc/gcc/prefix-map-realpath.patch
new file mode 100644
index 0000000000..3544f61a74
--- /dev/null
+++ b/meta/recipes-devtools/gcc/gcc/prefix-map-realpath.patch
@@ -0,0 +1,62 @@
+Relative paths don't work with -fdebug-prefix-map and friends. This
+can lead to paths which the user wanted to be remapped being missed.
+Setting -fdebug-prefix-map to work with a relative path isn't practical
+either.
+
+Instead, call gcc's realpath function on the incomming path name before
+comparing it with the remapping. This means other issues like symlinks
+are also accounted for and leads to a more consistent remapping experience.
+
+Upstream-Status: Pending [need to see if gcc developers would accept this]
+Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
+
+
+Index: gcc-12.1.0/gcc/file-prefix-map.cc
+===================================================================
+--- gcc-12.1.0.orig/gcc/file-prefix-map.cc
++++ gcc-12.1.0/gcc/file-prefix-map.cc
+@@ -70,19 +70,28 @@ remap_filename (file_prefix_map *maps, c
+   file_prefix_map *map;
+   char *s;
+   const char *name;
++  char *realname;
+   size_t name_len;
+ 
++  if (lbasename (filename) == filename)
++    return filename;
++
++  realname = lrealpath (filename);
++
+   for (map = maps; map; map = map->next)
+-    if (filename_ncmp (filename, map->old_prefix, map->old_len) == 0)
++    if (filename_ncmp (realname, map->old_prefix, map->old_len) == 0)
+       break;
+-  if (!map)
++  if (!map) {
++    free (realname);
+     return filename;
+-  name = filename + map->old_len;
++  }
++  name = realname + map->old_len;
+   name_len = strlen (name) + 1;
+ 
+   s = (char *) ggc_alloc_atomic (name_len + map->new_len);
+   memcpy (s, map->new_prefix, map->new_len);
+   memcpy (s + map->new_len, name, name_len);
++  free (realname);
+   return s;
+ }
+ 
+Index: gcc-12.1.0/libcpp/macro.cc
+===================================================================
+--- gcc-12.1.0.orig/libcpp/macro.cc
++++ gcc-12.1.0/libcpp/macro.cc
+@@ -563,7 +563,7 @@ _cpp_builtin_macro_text (cpp_reader *pfi
+ 	    if (!name)
+ 	      abort ();
+ 	  }
+-	if (pfile->cb.remap_filename)
++	if (pfile->cb.remap_filename && !pfile->state.in_directive)
+ 	  name = pfile->cb.remap_filename (name);
+ 	len = strlen (name);
+ 	buf = _cpp_unaligned_alloc (pfile, len * 2 + 3);