cmd/sharefs: check option parsing behaviour

This change makes it possible to check parseOpts behaviour as part of Go tests.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/sharefs/fuse.go

@@ -24,6 +24,7 @@ import (
 	"os"
 	"os/exec"
 	"os/signal"
+	"path"
 	"runtime"
 	"runtime/cgo"
 	"strconv"
@@ -43,6 +44,9 @@ type (
 	// closure represents a C function pointer.
 	closure = C.closure
 
+	// fuseArgs represents the fuse_args structure.
+	fuseArgs = C.struct_fuse_args
+
 	// setupState holds state used for setup. Its cgo handle is included in
 	// sharefs_private and considered opaque to non-setup callbacks.
 	setupState struct {
@@ -127,7 +131,14 @@ func sharefs_destroy(private_data unsafe.Pointer) {
 }
 
 // showHelp prints the help message.
-func showHelp(args *C.struct_fuse_args) {
+func showHelp(args *fuseArgs) {
+	executableName := sharefsName
+	if args.argc > 0 {
+		executableName = path.Base(C.GoString(*args.argv))
+	} else if name, err := os.Executable(); err == nil {
+		executableName = path.Base(name)
+	}
+
 	fmt.Printf("usage: %s [options] <mountpoint>\n\n", executableName)
 
 	fmt.Println("Filesystem options:")
@@ -141,7 +152,7 @@ func showHelp(args *C.struct_fuse_args) {
 }
 
 // parseOpts parses fuse options via fuse_opt_parse.
-func parseOpts(args *C.struct_fuse_args, setup *setupState) (ok bool) {
+func parseOpts(args *fuseArgs, setup *setupState, log *log.Logger) (ok bool) {
 	var unsafeOpts struct {
 		// Pathname to writable source directory.
 		source *C.char
@@ -233,25 +244,28 @@ func parseOpts(args *C.struct_fuse_args, setup *setupState) (ok bool) {
 	return true
 }
 
-// copyStrings returns a copy of s with null-termination.
-func copyStrings(s ...string) **C.char {
+// copyArgs returns a heap allocated copy of an argument slice in fuse_args representation.
+func copyArgs(s ...string) fuseArgs {
 	if len(s) == 0 {
-		return nil
+		return fuseArgs{argc: 0, argv: nil, allocated: 0}
 	}
 	args := unsafe.Slice((**C.char)(C.malloc(C.size_t(uintptr(len(s))*unsafe.Sizeof(s[0])))), len(s))
 	for i, arg := range s {
 		args[i] = C.CString(arg)
 	}
-	return &args[0]
+	return fuseArgs{argc: C.int(len(s)), argv: &args[0], allocated: 1}
 }
 
+// freeArgs frees the contents of argument list.
+func freeArgs(args *fuseArgs) { C.fuse_opt_free_args(args) }
+
 // unsafeAddArgument adds an argument to fuseArgs via fuse_opt_add_arg.
 // The last byte of arg must be 0.
-func unsafeAddArgument(args *C.struct_fuse_args, arg string) {
+func unsafeAddArgument(args *fuseArgs, arg string) {
 	C.fuse_opt_add_arg(args, (*C.char)(unsafe.Pointer(unsafe.StringData(arg))))
 }
 
-func _main(argc int, argv **C.char) (exitCode int) {
+func _main(s ...string) (exitCode int) {
 	msg := message.New(log.Default())
 	container.TryArgv0(msg)
 	runtime.LockOSThread()
@@ -262,7 +276,8 @@ func _main(argc int, argv **C.char) (exitCode int) {
 	var pinner runtime.Pinner
 	defer pinner.Unpin()
 
-	args := C.struct_fuse_args{argc: C.int(argc), argv: argv, allocated: 1}
+	args := copyArgs(s...)
+	defer freeArgs(&args)
 
 	// this causes the kernel to enforce access control based on
 	// struct stat populated by sharefs_getattr
@@ -278,12 +293,9 @@ func _main(argc int, argv **C.char) (exitCode int) {
 	if C.fuse_parse_cmdline(&args, &opts) != 0 {
 		return 1
 	}
-	defer func() {
-		if opts.mountpoint != nil {
-			C.free(unsafe.Pointer(opts.mountpoint))
-		}
-		C.fuse_opt_free_args(&args)
-	}()
+	if opts.mountpoint != nil {
+		defer C.free(unsafe.Pointer(opts.mountpoint))
+	}
 
 	if opts.show_version != 0 {
 		fmt.Println("hakurei version", info.Version())
@@ -315,7 +327,7 @@ func _main(argc int, argv **C.char) (exitCode int) {
 		os.Args[pathnameArg] = container.Nonexistent
 	}
 
-	if !parseOpts(&args, &setup) {
+	if !parseOpts(&args, &setup, msg.GetLogger()) {
 		return 1
 	}