Re: [PATCH 1/2] Kbuild: enable -fms-extensions

[Nathan Chancellor <nathan@kernel.org>]

On Wed, Oct 22, 2025 at 11:11:38PM +0200, Nathan Chancellor wrote:
...
> > > > +# Allow including a tagged struct or union anonymously in another struct/union.
> > > > +KBUILD_CFLAGS += -fms-extensions
...
> I have tentatively applied this to kbuild-next so that it can spend most
> of the cycle in -next to try and catch all potential problems.

One side effect that has been found in my testing so far is clang's
'-fms-extensions' turns '_inline' into a keyword, which breaks fs/jfs:

  In file included from fs/jfs/jfs_unicode.c:8:
  fs/jfs/jfs_incore.h:86:13: error: type name does not allow function specifier to be specified
     86 |                                         unchar _inline[128];
        |                                                ^
  fs/jfs/jfs_incore.h:86:20: error: expected member name or ';' after declaration specifiers
     86 |                                         unchar _inline[128];
        |                                         ~~~~~~~~~~~~~~^

There appear to be other similar keywords (ones with KEYMS in the linke
below) but my personal distribution configuration does not show any
instances in the build where they matter (I did not test allmodconfig
yet).

  https://github.com/llvm/llvm-project/blob/249883d0c5883996bed038cd82a8999f342994c9/clang/include/clang/Basic/TokenKinds.def#L744-L794

Something like this is all it takes to resolve the issue, so I will send
a patch for formal review/acking but I wanted to bring it up ahead of
time in case this is unpalpable and we should throw these changes out of
-next instead of forward fixing.

Cheers,
Nathan

diff --git a/fs/jfs/jfs_incore.h b/fs/jfs/jfs_incore.h
index 10934f9a11be..5aaafedb8fbc 100644
--- a/fs/jfs/jfs_incore.h
+++ b/fs/jfs/jfs_incore.h
@@ -76,14 +76,14 @@ struct jfs_inode_info {
 		struct {
 			unchar _unused[16];	/* 16: */
 			dxd_t _dxd;		/* 16: */
-			/* _inline may overflow into _inline_ea when needed */
+			/* _inline_sym may overflow into _inline_ea when needed */
 			/* _inline_ea may overlay the last part of
 			 * file._xtroot if maxentry = XTROOTINITSLOT
 			 */
 			union {
 				struct {
 					/* 128: inline symlink */
-					unchar _inline[128];
+					unchar _inline_sym[128];
 					/* 128: inline extended attr */
 					unchar _inline_ea[128];
 				};
@@ -101,7 +101,7 @@ struct jfs_inode_info {
 #define i_imap u.file._imap
 #define i_dirtable u.dir._table
 #define i_dtroot u.dir._dtroot
-#define i_inline u.link._inline
+#define i_inline u.link._inline_sym
 #define i_inline_ea u.link._inline_ea
 #define i_inline_all u.link._inline_all