Support the FUSE 3 build on macOS with macFUSE 5

macFUSE 5 ships a libfuse 3 whose operation signatures default to
Darwin-specific types (struct fuse_darwin_attr, struct statfs, a
Darwin directory filler). Define FUSE_DARWIN_ENABLE_EXTENSIONS=0 in
ltfs_fuse_version.h so the upstream-compatible signatures are used;
the library exports both symbol flavors.

The macFUSE position argument of the xattr handlers exists only in
the fuse2 API and the Darwin-extension mode, so the FUSE 3 build now
uses the upstream xattr signatures (LTFS_XATTR_POSITION).

Verified on macOS 26 (arm64) against the macFUSE 5.2.0 SDK
(libfuse 3.18.2): autotools (--with-fuse2=no) and CMake
(-DLTFS_WITH_FUSE2=OFF) both build without new warnings, link
libfuse3.4.dylib, and the binaries run; parallel_direct_writes is
detected. The macOS fuse2 builds and the Linux test suites
(autotools make check and ctest, 14/14) are unaffected.

Author: matejk

README.md

@@ -201,7 +201,9 @@ make install
 On Linux the build uses libfuse 3 (package `libfuse3-dev` on Debian/Ubuntu,
 `fuse3-devel` on Fedora/RHEL). Pass `--with-fuse2` to build against the
 legacy libfuse 2 API instead; macOS, FreeBSD, and NetBSD currently use the
-libfuse 2 API by default.
+libfuse 2 API by default. On macOS with macFUSE 5 or later, which ships a
+libfuse 3, the FUSE 3 build can be selected with `--with-fuse2=no`
+(autotools) or `-DLTFS_WITH_FUSE2=OFF` (CMake).
 
 FUSE 3 builds negotiate request sizes up to 1 MiB (tunable with
 `-o max_write=<bytes>`), serve directory listings through readdirplus, and

src/libltfs/ltfs_fuse_version.h

@@ -54,6 +54,12 @@
  * (default on Linux; --with-fuse2 selects the libfuse 2 API). */
 #ifdef HAVE_FUSE3
 #define FUSE_USE_VERSION 31
+/* macFUSE 5's libfuse3 defaults to Darwin-specific operation signatures
+ * (struct fuse_darwin_attr, struct statfs, ...). Request the upstream-
+ * compatible API instead; the library exports both symbol flavors. */
+#ifdef __APPLE__
+#define FUSE_DARWIN_ENABLE_EXTENSIONS 0
+#endif
 #else
 #define FUSE_USE_VERSION 26
 #endif

src/ltfs_fuse.c

@@ -104,6 +104,13 @@ static struct fuse_context *context;
 int ltfs_fuse_fgetattr(const char *path, struct stat *stbuf, struct fuse_file_info *fi);
 int ltfs_fuse_ftruncate(const char *path, off_t length, struct fuse_file_info *fi);
 
+/* The fuse2 macFUSE API adds a position argument to the xattr handlers; the
+ * fuse3 build uses the upstream signatures (Darwin extensions disabled in
+ * ltfs_fuse_version.h). */
+#if defined(__APPLE__) && !defined(HAVE_FUSE3)
+#define LTFS_XATTR_POSITION 1
+#endif
+
 #if !defined(__APPLE__) && FUSE_VERSION > 27
 /* Per-open cache policy. With -o direct_io every read and write bypasses
  * the kernel page cache: requests arrive at the application's I/O size
@@ -1135,13 +1142,13 @@ int ltfs_fuse_read(const char *path, char *buf, size_t size, off_t offset, struc
 	return errormap_fuse_error(ret);
 }
 
-#ifdef __APPLE__
+#ifdef LTFS_XATTR_POSITION
 int ltfs_fuse_setxattr(const char *path, const char *name, const char *value, size_t size,
 	int flags, uint32_t position)
 #else
 int ltfs_fuse_setxattr(const char *path, const char *name, const char *value, size_t size,
 	int flags)
-#endif /* __APPLE__ */
+#endif /* LTFS_XATTR_POSITION */
 {
 	struct ltfs_fuse_data *priv = fuse_get_context()->private_data;
 	ltfs_file_id id;
@@ -1155,14 +1162,14 @@ int ltfs_fuse_setxattr(const char *path, const char *name, const char *value, si
 	 * on OS X, and we have no resource forks
 	 * TODO: is it correct to behave this way?
 	 */
-#ifdef __APPLE__
+#ifdef LTFS_XATTR_POSITION
 	if (position) {
 		/* Position argument must be zero */
 		ltfsmsg(LTFS_ERR, 14023E);
 		ltfs_request_trace(FUSE_REQ_EXIT(REQ_SETXATTR), -EINVAL, 0);
 		return -EINVAL;
 	}
-#endif /* __APPLE__ */
+#endif /* LTFS_XATTR_POSITION */
 
 	ret = ltfs_fsops_setxattr(path, name, value, size, flags, &id, priv->data);
 
@@ -1171,12 +1178,12 @@ int ltfs_fuse_setxattr(const char *path, const char *name, const char *value, si
 	return errormap_fuse_error(ret);
 }
 
-#ifdef __APPLE__
+#ifdef LTFS_XATTR_POSITION
 int ltfs_fuse_getxattr(const char *path, const char *name, char *value, size_t size,
 	uint32_t position)
 #else
 int ltfs_fuse_getxattr(const char *path, const char *name, char *value, size_t size)
-#endif /* __APPLE__ */
+#endif /* LTFS_XATTR_POSITION */
 {
 	struct ltfs_fuse_data *priv = fuse_get_context()->private_data;
 	ltfs_file_id id;
@@ -1190,7 +1197,7 @@ int ltfs_fuse_getxattr(const char *path, const char *name, char *value, size_t s
 	 * on OS X, and we have no resource forks
 	 * TODO: is it correct to behave this way?
 	 */
-#ifdef __APPLE__
+#ifdef LTFS_XATTR_POSITION
 	if (position) {
 		/* Position argument must be zero */
 		ltfsmsg(LTFS_ERR, 14024E);
@@ -1204,7 +1211,7 @@ int ltfs_fuse_getxattr(const char *path, const char *name, char *value, size_t s
 		ltfs_request_trace(FUSE_REQ_EXIT(REQ_GETXATTR), -LTFS_NO_XATTR, 0);
 		return errormap_fuse_error(-LTFS_NO_XATTR);
 	}
-#endif /* __APPLE__ */
+#endif /* LTFS_XATTR_POSITION */
 
 	ret = ltfs_fsops_getxattr(path, name, value, size, &id, priv->data);