mount.c.diff

diff -ur a/lib/mount.c b/lib/mount.c
--- a/lib/mount.c
+++ b/lib/mount.c
@@ -46,7 +46,6 @@
 #define umount2(mnt, flags) unmount(mnt, (flags == 2) ? MNT_FORCE : 0)
 #endif
 
-#define FUSERMOUNT_PROG		"fusermount3"
 #define FUSE_COMMFD_ENV		"_FUSE_COMMFD"
 #define FUSE_COMMFD2_ENV	"_FUSE_COMMFD2"
 
@@ -121,6 +120,35 @@
 	FUSE_OPT_END
 };
 
+/**
+ * Returns FUSERMOUNT_PROG path from environment variable.
+ *
+ * If $FUSERMOUNT_PROG is not set, the program exits.
+ * 
+ * Call with FUSERMOUNT_PROG_DEBUG=nonzerovalue to make the code print the value before evaluation.
+ */
+static const char *fusermountProg(void)
+{
+	static const char envVar[] = "FUSERMOUNT_PROG";
+	char *fusermountProg = getenv(envVar);
+
+	static const char debugEnvVarSuffix[] = "_DEBUG";
+	char debugEnvVar[sizeof(envVar) + sizeof(debugEnvVarSuffix) + 1];
+	sprintf(debugEnvVar, "%s%s", envVar, debugEnvVarSuffix);
+
+	if (fusermountProg == NULL) {
+		fprintf(stderr, "Error: $%s not set\n", envVar);
+		exit(1);
+	}
+
+	if (getenv(debugEnvVar) != NULL) {
+		fprintf(stderr, "$%s: %s\n", envVar, fusermountProg);
+	}
+
+	return fusermountProg;
+}
+
+
 /*
  * Running fusermount by calling 'posix_spawn'
  *
@@ -129,19 +157,13 @@
 static int fusermount_posix_spawn(posix_spawn_file_actions_t *action,
 				  char const * const argv[], pid_t *out_pid)
 {
-	const char *full_path = FUSERMOUNT_DIR "/" FUSERMOUNT_PROG;
 	pid_t pid;
 
 	/* See man 7 environ for the global environ pointer */
 
 	/* first try the install path */
-	int status = posix_spawn(&pid, full_path,  action, NULL,
+	int status = posix_spawn(&pid, fusermountProg(),  action, NULL,
 				 (char * const *) argv, environ);
-	if (status != 0) {
-		/* if that fails, try a system install */
-		status = posix_spawnp(&pid, FUSERMOUNT_PROG, action, NULL,
-				      (char * const *) argv, environ);
-	}
 
 	if (status != 0) {
 		fuse_log(FUSE_LOG_ERR,
@@ -160,12 +182,12 @@
 
 void fuse_mount_version(void)
 {
-	char const *const argv[] = {FUSERMOUNT_PROG, "--version", NULL};
+	char const *const argv[] = {fusermountProg(), "--version", NULL};
 	int status = fusermount_posix_spawn(NULL, argv, NULL);
 
 	if(status != 0)
 		fuse_log(FUSE_LOG_ERR, "Running '%s --version' failed",
-			 FUSERMOUNT_PROG);
+			 fusermountProg());
 }
 
 struct mount_flags {
@@ -337,12 +359,12 @@
 		return;
 
 	char const * const argv[] =
-		{ FUSERMOUNT_PROG, "--unmount", "--quiet", "--lazy",
+		{ fusermountProg(), "--unmount", "--quiet", "--lazy",
 				"--", mountpoint, NULL };
 	int status = fusermount_posix_spawn(NULL, argv, NULL);
 	if(status != 0) {
 		fuse_log(FUSE_LOG_ERR, "Spawning %s to unmount failed: %s",
-			 FUSERMOUNT_PROG, strerror(-status));
+			 fusermountProg(), strerror(-status));
 		return;
 	}
 }
@@ -378,7 +400,7 @@
 	setenv(FUSE_COMMFD2_ENV, arg_fd_entry, 1);
 
 	char const *const argv[] = {
-		FUSERMOUNT_PROG,
+		fusermountProg(),
 		"--auto-unmount",
 		"--",
 		mountpoint,
@@ -434,7 +456,7 @@
 	res = socketpair(PF_UNIX, SOCK_STREAM, 0, fds);
 	if(res == -1) {
 		fuse_log(FUSE_LOG_ERR, "Running %s: socketpair() failed: %s\n",
-			 FUSERMOUNT_PROG, strerror(errno));
+			 fusermountProg(), strerror(errno));
 		return -1;
 	}
 
@@ -451,7 +473,7 @@
 	setenv(FUSE_COMMFD2_ENV, arg_fd_entry, 1);
 
 	char const *const argv[] = {
-		FUSERMOUNT_PROG,
+		fusermountProg(),
 		"-o", opts ? opts : "",
 		"--",
 		mountpoint,
@@ -476,7 +498,7 @@
 		close(fds[0]);
 		close(fds[1]);
 		fuse_log(FUSE_LOG_ERR, "posix_spawn(p)() for %s failed: %s",
-			 FUSERMOUNT_PROG, strerror(-status));
+			 fusermountProg(), strerror(-status));
 		return -1;
 	}