librclone: add RcloneFreeString function

See PR #5703

Based on initial work by Weng Haoyu (@wengh) in PR #5362

librclone/README.md

@@ -31,6 +31,7 @@ For documentation see the Go documentation for:
 - [RcloneInitialize](https://pkg.go.dev/github.com/rclone/rclone/librclone#RcloneInitialize)
 - [RcloneFinalize](https://pkg.go.dev/github.com/rclone/rclone/librclone#RcloneFinalize)
 - [RcloneRPC](https://pkg.go.dev/github.com/rclone/rclone/librclone#RcloneRPC)
+- [RcloneFreeString](https://pkg.go.dev/github.com/rclone/rclone/librclone#RcloneFreeString)
 
 ### C Example
 

librclone/librclone.go

@@ -20,6 +20,8 @@
 package main
 
 /*
+#include <stdlib.h>
+
 struct RcloneRPCResult {
 	char*	Output;
 	int	Status;
@@ -28,6 +30,8 @@ struct RcloneRPCResult {
 import "C"
 
 import (
+	"unsafe"
+
 	"github.com/rclone/rclone/librclone/librclone"
 
 	_ "github.com/rclone/rclone/backend/all"   // import all backends
@@ -79,5 +83,17 @@ func RcloneRPC(method *C.char, input *C.char) (result C.struct_RcloneRPCResult)
 	return result
 }
 
+// RcloneFreeString may be used to free the string returned by RcloneRPC
+//
+// If the caller has access to the C standard library, the free function can
+// normally be called directly instead. In some cases the caller uses a
+// runtime library which is not compatible, and then this function can be
+// used to release the memory with the same library that allocated it.
+//
+//export RcloneFreeString
+func RcloneFreeString(str *C.char) {
+	C.free(unsafe.Pointer(str))
+}
+
 // do nothing here - necessary for building into a C library
 func main() {}