InnoDB: Detect the availability of the Mac OS X fsync() work-around

at run-time, so that an executable compiled on Mac OS X 10.2 can
be run on Mac OS X 10.2 (without the work-around) and Mac OS X 10.3
and later with the work-aroud enabled.


innobase/include/srv0start.h:
  Mac OS X: Add srv_have_fullfsync
innobase/os/os0file.c:
  os_file_flush(): Use F_FULLFSYNC on Mac OS X 10.3, but not on 10.2
innobase/srv/srv0start.c:
  innobase_start_or_create_for_mysql(): When compiled on OS X 10.2,
  detect if the binary is running on OS X 10.3 or later, and set
  srv_have_fullfsync accordingly.

innobase/include/srv0start.h

@@ -75,6 +75,10 @@ extern	dulint	srv_start_lsn;
 void set_panic_flag_for_netware(void);
 #endif
 
+#ifdef HAVE_DARWIN_THREADS
+extern	ibool	srv_have_fullfsync;
+#endif
+
 extern  ulint   srv_sizeof_trx_t_in_ha_innodb_cc;
 
 extern  ibool   srv_is_being_started;

innobase/os/os0file.c

@@ -1763,19 +1763,31 @@ os_file_flush(
 #else
 	int	ret;
 
-#if defined(HAVE_DARWIN_THREADS) && defined(F_FULLFSYNC) 
+#if defined(HAVE_DARWIN_THREADS)
+# ifndef F_FULLFSYNC
+	/* The following definition is from the Mac OS X 10.3 <sys/fcntl.h> */
+#  define F_FULLFSYNC 51 /* fsync + ask the drive to flush to the media */
+# elif F_FULLFSYNC != 51
+#  error "F_FULLFSYNC != 51: ABI incompatibility with Mac OS X 10.3"
+# endif
 	/* Apple has disabled fsync() for internal disk drives in OS X. That
 	caused corruption for a user when he tested a power outage. Let us in
 	OS X use a nonstandard flush method recommended by an Apple
 	engineer. */
 
-	ret = fcntl(file, F_FULLFSYNC, NULL);
-
-	if (ret) {
-		/* If we are not on a file system that supports this, then
-		fall back to a plain fsync. */ 
+	if (!srv_have_fullfsync) {
+		/* If we are not on an operating system that supports this,
+		then fall back to a plain fsync. */ 
 
 		ret = fsync(file);
+	} else {
+		ret = fcntl(file, F_FULLFSYNC, NULL);
+
+		if (ret) {
+			/* If we are not on a file system that supports this,
+			then fall back to a plain fsync. */ 
+			ret = fsync(file);
+		}
 	}
 #elif HAVE_FDATASYNC
 	ret = fdatasync(file);

innobase/srv/srv0start.c

@@ -61,6 +61,11 @@ dulint		srv_start_lsn;
 /* Log sequence number at shutdown */
 dulint		srv_shutdown_lsn;
 
+#ifdef HAVE_DARWIN_THREADS
+# include <sys/utsname.h>
+ibool		srv_have_fullfsync = FALSE;
+#endif
+
 ibool		srv_start_raw_disk_in_use  = FALSE;
 
 static ibool	srv_start_has_been_called  = FALSE;
@@ -935,6 +940,28 @@ innobase_start_or_create_for_mysql(void)
 	ulint	i;
 	ibool	srv_file_per_table_original_value  = srv_file_per_table;
 	mtr_t   mtr;
+#ifdef HAVE_DARWIN_THREADS
+# ifdef F_FULLFSYNC
+	/* This executable has been compiled on Mac OS X 10.3 or later.
+	Assume that F_FULLFSYNC is available at run-time. */
+	srv_have_fullfsync = TRUE;
+# else /* F_FULLFSYNC */
+	/* This executable has been compiled on Mac OS X 10.2
+	or earlier.  Determine if the executable is running
+	on Mac OS X 10.3 or later. */
+	struct utsname utsname;
+	if (uname(&utsname)) {
+		fputs("InnoDB: cannot determine Mac OS X version!\n", stderr);
+	} else {
+		srv_have_fullfsync = strcmp(utsname.release, "7.") >= 0;
+	}
+	if (!srv_have_fullfsync) {
+		fputs(
+"InnoDB: On Mac OS X, fsync() may be broken on internal drives,\n"
+"InnoDB: making transactions unsafe!\n", stderr);
+	}
+# endif /* F_FULLFSYNC */
+#endif /* HAVE_DARWIN_THREADS */
 
 	if (sizeof(ulint) != sizeof(void*)) {
 		fprintf(stderr,