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[PATCH] compat: convert modes to use portable file type values

From
David Michael <fedora.dm0@gmail.com>
Date
Nov 30, 2014, 02:41 UTC
Message-ID
<87vblxl8ah.fsf@gmail.com>

This adds simple wrapper functions around calls to stat(), fstat(), and lstat() that translate the operating system's native file type bits to those used by most operating systems. It also rewrites the S_IF* macros to the common values, so all file type processing is performed using the translated modes. This makes projects portable across operating systems that use different file type definitions.

Only the file type bits may be affected by these compatibility functions; the file permission bits are assumed to be 07777 and are passed through unchanged.

Signed-off-by: David Michael <fedora.dm0@gmail.com>
---
Hi,

This is my most recent attempt at solving the problem of z/OS using different file type values than every other OS. I believe it should be safe as long as the file type bits don't ever need to be converted back to their native values (and I didn't see any instances of that).

I've been testing it by making commits to the same repositories on different operating systems and pushing those changes around, and so far there have been no issues.

Can anyone foresee any problems with this method?
Thanks.
David
 Makefile          |  8 ++++++++
 cache.h           |  7 -------
 compat/stat.c     | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 configure.ac      | 22 ++++++++++++++++++++++
 git-compat-util.h | 32 ++++++++++++++++++++++++++++++++
 5 files changed, 111 insertions(+), 7 deletions(-)
 create mode 100644 compat/stat.c
diff --git a/Makefile b/Makefile
index 827006b..cba3be1 100644
--- a/Makefile
+++ b/Makefile
@@ -191,6 +191,10 @@ all::
 # Define NO_TRUSTABLE_FILEMODE if your filesystem may claim to support
 # the executable mode bit, but doesn't really do so.
 #
+# Define NEEDS_MODE_TRANSLATION if your OS strays from the typical file type
+# bits in mode values (e.g. z/OS defines I_SFMT to 0xFF000000 as opposed to the
+# usual 0xF000).
+#
 # Define NO_IPV6 if you lack IPv6 support and getaddrinfo().
 #
 # Define NO_UNIX_SOCKETS if your system does not offer unix sockets.
@@ -1230,6 +1234,10 @@ endif
 ifdef NO_TRUSTABLE_FILEMODE
 	BASIC_CFLAGS += -DNO_TRUSTABLE_FILEMODE
 endif
+ifdef NEEDS_MODE_TRANSLATION
+	COMPAT_CFLAGS += -DNEEDS_MODE_TRANSLATION
+	COMPAT_OBJS += compat/stat.o
+endif
 ifdef NO_IPV6
 	BASIC_CFLAGS += -DNO_IPV6
 endif
diff --git a/cache.h b/cache.h
index 99ed096..f8174fe 100644
--- a/cache.h
+++ b/cache.h
@@ -65,13 +65,6 @@ unsigned long git_deflate_bound(git_zstream *, unsigned long);
  *
  * The value 0160000 is not normally a valid mode, and
  * also just happens to be S_IFDIR + S_IFLNK
- *
- * NOTE! We *really* shouldn't depend on the S_IFxxx macros
- * always having the same values everywhere. We should use
- * our internal git values for these things, and then we can
- * translate that to the OS-specific value. It just so
- * happens that everybody shares the same bit representation
- * in the UNIX world (and apparently wider too..)
  */
 #define S_IFGITLINK	0160000
 #define S_ISGITLINK(m)	(((m) & S_IFMT) == S_IFGITLINK)
diff --git a/compat/stat.c b/compat/stat.c
new file mode 100644
index 0000000..0ff1f2f
--- /dev/null
+++ b/compat/stat.c
@@ -0,0 +1,49 @@
+#define _POSIX_SOURCE
+#include <stddef.h>    /* NULL         */
+#include <sys/stat.h>  /* *stat, S_IS* */
+#include <sys/types.h> /* mode_t       */
+
+static inline mode_t mode_native_to_git(mode_t native_mode)
+{
+	if (S_ISREG(native_mode))
+		return 0100000 | (native_mode & 07777);
+	else if (S_ISDIR(native_mode))
+		return 0040000 | (native_mode & 07777);
+	else if (S_ISLNK(native_mode))
+		return 0120000 | (native_mode & 07777);
+	else if (S_ISBLK(native_mode))
+		return 0060000 | (native_mode & 07777);
+	else if (S_ISCHR(native_mode))
+		return 0020000 | (native_mode & 07777);
+	else if (S_ISFIFO(native_mode))
+		return 0010000 | (native_mode & 07777);
+	else /* Non-standard type bits were given. */
+		return native_mode & 07777;
+}
+
+int git_stat(const char *path, struct stat *buf)
+{
+	int rc;
+	rc = stat(path, buf);
+	if (buf != NULL)
+		buf->st_mode = mode_native_to_git(buf->st_mode);
+	return rc;
+}
+
+int git_fstat(int fd, struct stat *buf)
+{
+	int rc;
+	rc = fstat(fd, buf);
+	if (buf != NULL)
+		buf->st_mode = mode_native_to_git(buf->st_mode);
+	return rc;
+}
+
+int git_lstat(const char *path, struct stat *buf)
+{
+	int rc;
+	rc = lstat(path, buf);
+	if (buf != NULL)
+		buf->st_mode = mode_native_to_git(buf->st_mode);
+	return rc;
+}
diff --git a/configure.ac b/configure.ac
index 6af9647..b8eced4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -873,6 +873,28 @@ else
 	SNPRINTF_RETURNS_BOGUS=
 fi
 GIT_CONF_SUBST([SNPRINTF_RETURNS_BOGUS])
+#
+# Define NEEDS_MODE_TRANSLATION if your OS strays from the typical file type
+# bits in mode values.
+AC_CACHE_CHECK([whether the platform uses typical file type bits],
+ [ac_cv_sane_mode_bits], [
+AC_EGREP_CPP(yippeeyeswehaveit,
+	AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT],
+[#if S_IFMT == 0170000 && \
+	S_IFREG == 0100000 && S_IFDIR == 0040000 && S_IFLNK == 0120000 && \
+	S_IFBLK == 0060000 && S_IFCHR == 0020000 && S_IFIFO == 0010000
+yippeeyeswehaveit
+#endif
+]),
+	[ac_cv_sane_mode_bits=yes],
+	[ac_cv_sane_mode_bits=no])
+])
+if test $ac_cv_sane_mode_bits = yes; then
+	NEEDS_MODE_TRANSLATION=
+else
+	NEEDS_MODE_TRANSLATION=UnfortunatelyYes
+fi
+GIT_CONF_SUBST([NEEDS_MODE_TRANSLATION])
 
 
 ## Checks for library functions.
diff --git a/git-compat-util.h b/git-compat-util.h
index 400e921..48f6910 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -474,6 +474,38 @@ extern int git_munmap(void *start, size_t length);
 #define on_disk_bytes(st) ((st).st_blocks * 512)
 #endif
 
+#ifdef NEEDS_MODE_TRANSLATION
+#undef S_IFMT
+#undef S_IFREG
+#undef S_IFDIR
+#undef S_IFLNK
+#undef S_IFBLK
+#undef S_IFCHR
+#undef S_IFIFO
+#define S_IFMT  0170000
+#define S_IFREG 0100000
+#define S_IFDIR 0040000
+#define S_IFLNK 0120000
+#define S_IFBLK 0060000
+#define S_IFCHR 0020000
+#define S_IFIFO 0010000
+#ifdef stat
+#undef stat
+#endif
+#define stat(path, buf) git_stat(path, buf)
+extern int git_stat(const char *, struct stat *);
+#ifdef fstat
+#undef fstat
+#endif
+#define fstat(fd, buf) git_fstat(fd, buf)
+extern int git_fstat(int, struct stat *);
+#ifdef lstat
+#undef lstat
+#endif
+#define lstat(path, buf) git_lstat(path, buf)
+extern int git_lstat(const char *, struct stat *);
+#endif
+
 #define DEFAULT_PACKED_GIT_LIMIT \
 	((1024L * 1024L) * (sizeof(void*) >= 8 ? 8192 : 256))
 

-- 
1.9.3
Next: Torsten Bögershausen
Message 1 of 12 in “compat: convert modes to use portable file type values”
  1. compat: convert modes to use portable file type valuesDavid Michael, Nov 30, 2014
  2. Torsten BögershausenNov 30, 2014
  3. David MichaelDec 1, 2014
  4. Torsten BögershausenDec 1, 2014
  5. David MichaelDec 1, 2014
  6. David MichaelDec 1, 2014
  7. Junio C HamanoDec 1, 2014
  8. Duy NguyenDec 1, 2014
  9. David MichaelDec 1, 2014
  10. Junio C HamanoDec 1, 2014
  11. David MichaelDec 1, 2014
  12. Junio C HamanoDec 1, 2014

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