From e20e5c9ae574bba8827310edf38ae9edca08c469 Mon Sep 17 00:00:00 2001
From: Nikolaus Rath <Nikolaus@rath.org>
Date: Sat, 1 Oct 2016 11:24:46 -0700
Subject: [PATCH] Improve documentation of argument parsing.

---
 include/fuse.h          |  7 +++++++
 include/fuse_common.h   | 16 +++++++++++++---
 include/fuse_lowlevel.h |  7 +++++++
 lib/fuse.c              |  5 +++++
 lib/fuse_lowlevel.c     |  1 +
 lib/helper.c            |  1 +
 lib/mount.c             |  2 ++
 lib/mount_bsd.c         |  2 ++
 8 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/include/fuse.h b/include/fuse.h
index c70d2fe..5721caa 100644
--- a/include/fuse.h
+++ b/include/fuse.h
@@ -640,6 +640,13 @@ struct fuse_context {
 /**
  * Create a new FUSE filesystem.
  *
+ * Known parameters in `args` are removed. If there are any unknown
+ * arguments, an error is printed to stderr and the function returns
+ * NULL.
+ *
+ * If the --help or --version parameters are specified, the function
+ * prints the requested information to stdout and returns NULL.
+ *
  * @param ch the communication channel
  * @param args argument vector
  * @param op the filesystem operations
diff --git a/include/fuse_common.h b/include/fuse_common.h
index 2fa9962..df92e8e 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -213,7 +213,13 @@ struct fuse_pollhandle;
  * Create a FUSE mountpoint
  *
  * Returns a control file descriptor suitable for passing to
- * fuse_new()
+ * fuse_new(). Unknown parameters in `args` are passed through
+ * unchanged. Known parameters (with the exception of --help and
+ * --version) are removed from `args`.
+ *
+ * If the --help or --version parameters are specified, the function
+ * prints the requested information to stdout and returns a valid
+ * pointer. However, it does not actually perform the mount.
  *
  * @param mountpoint the mount point path
  * @param args argument vector
@@ -230,7 +236,7 @@ struct fuse_chan *fuse_mount(const char *mountpoint, struct fuse_args *args);
 void fuse_unmount(const char *mountpoint, struct fuse_chan *ch);
 
 /**
- * Parse common options
+ * Utility functions for simple file systems to parse common options.
  *
  * The following options are parsed:
  *
@@ -242,7 +248,11 @@ void fuse_unmount(const char *mountpoint, struct fuse_chan *ch);
  *   '-ofsname=..'   file system name, if not present, then set to the program
  *		     name
  *
- * All parameters may be NULL
+ * Unknown parameters in `args` are passed through unchanged. Known
+ * parameters (with the exception of --help and --version) are removed.
+ *
+ * All parameters may be NULL (in which case they may still
+ * be specified on the command line, but will not be set).
  *
  * @param args argument vector
  * @param mountpoint the returned mountpoint, should be freed after use
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index 2022cc6..ce39906 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -1575,6 +1575,13 @@ int fuse_req_interrupted(fuse_req_t req);
 /**
  * Create a low level session
  *
+ * Known parameters in `args` are removed. If there are any unknown
+ * arguments, an error is printed to stderr and the function returns
+ * NULL.
+ *
+ * If the --help or --version parameters are specified, the function
+ * prints the requsted information to stdout and returns NULL.
+ *
  * @param args argument vector
  * @param op the low level filesystem operations
  * @param op_size sizeof(struct fuse_lowlevel_ops)
diff --git a/lib/fuse.c b/lib/fuse.c
index a879ffa..cd254f9 100644
--- a/lib/fuse.c
+++ b/lib/fuse.c
@@ -4684,6 +4684,9 @@ struct fuse *fuse_new(struct fuse_chan *ch, struct fuse_args *args,
 	init_list_head(&f->full_slabs);
 	init_list_head(&f->lru_table);
 
+	/* When --help or --version are specified, we print messages
+	   to stderr but continue for now (and keep the arguments in
+	   `args` for use below */
 	if (fuse_opt_parse(args, &f->conf, fuse_lib_opts,
 			   fuse_lib_opt_proc) == -1)
 		goto out_free_fs;
@@ -4714,6 +4717,8 @@ struct fuse *fuse_new(struct fuse_chan *ch, struct fuse_args *args,
 	f->conf.readdir_ino = 1;
 #endif
 
+	/* This function will return NULL if there is an --help
+	   or --version argument in `args` */
 	f->se = fuse_lowlevel_new(args, &llop, sizeof(llop), f);
 	if (f->se == NULL) {
 		if (f->conf.help)
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 9b59515..31714dd 100755
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -2674,6 +2674,7 @@ static int fuse_ll_opt_proc(void *data, const char *arg, int key,
 		fprintf(stderr, "fuse: unknown option `%s'\n", arg);
 	}
 
+	/* Fail */
 	return -1;
 }
 
diff --git a/lib/helper.c b/lib/helper.c
index 97577c2..6a55269 100644
--- a/lib/helper.c
+++ b/lib/helper.c
@@ -114,6 +114,7 @@ static int fuse_helper_opt_proc(void *data, const char *arg, int key,
 		}
 
 	default:
+		/* Pass through unknown options */
 		return 1;
 	}
 }
diff --git a/lib/mount.c b/lib/mount.c
index 7be7b25..b2b841d 100644
--- a/lib/mount.c
+++ b/lib/mount.c
@@ -241,6 +241,8 @@ static int fuse_mount_opt_proc(void *data, const char *arg, int key,
 		mo->ishelp = 1;
 		break;
 	}
+
+	/* Pass through unknown options */
 	return 1;
 }
 
diff --git a/lib/mount_bsd.c b/lib/mount_bsd.c
index 3d6b12f..40ef93f 100644
--- a/lib/mount_bsd.c
+++ b/lib/mount_bsd.c
@@ -141,6 +141,8 @@ static int fuse_mount_opt_proc(void *data, const char *arg, int key,
 		mo->ishelp = 1;
 		break;
 	}
+
+	/* Pass through unknown options */
 	return 1;
 }
 
-- 
2.30.2