From d85d389b09a0c7805e2b7fb041c4ce7b1d0fd5a2 Mon Sep 17 00:00:00 2001
From: CGMossa <cgmossa@gmail.com>
Date: Mon, 3 Jun 2024 12:13:46 +0200
Subject: [PATCH] added routine to free the leaked rust `CString`. (#22)

---
 src/myrustlib/api.h        | 1 +
 src/myrustlib/src/hello.rs | 7 ++++++-
 src/wrapper.c              | 6 +++++-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/myrustlib/api.h b/src/myrustlib/api.h
index 16ad389..723e695 100644
--- a/src/myrustlib/api.h
+++ b/src/myrustlib/api.h
@@ -5,6 +5,7 @@ extern "C" {
 #endif
 
 char * string_from_rust(void);
+void free_string_from_rust(char*);
 int32_t random_number(void);
 void run_threads(void);
 
diff --git a/src/myrustlib/src/hello.rs b/src/myrustlib/src/hello.rs
index 925cc15..3186a21 100644
--- a/src/myrustlib/src/hello.rs
+++ b/src/myrustlib/src/hello.rs
@@ -2,7 +2,12 @@ use std::ffi::CString;
 use std::os::raw::c_char;
 
 #[no_mangle]
-pub extern fn string_from_rust() -> *const c_char {
+pub extern "C" fn string_from_rust() -> *const c_char {
     let s = CString::new("Hello ピカチュウ !").unwrap();
     s.into_raw()
 }
+
+#[no_mangle]
+pub extern "C" fn free_string_from_rust(ptr: *mut c_char) {
+    let _ = unsafe { CString::from_raw(ptr) };
+}
diff --git a/src/wrapper.c b/src/wrapper.c
index 23dac87..9e8f131 100644
--- a/src/wrapper.c
+++ b/src/wrapper.c
@@ -7,7 +7,11 @@
 
 // Actual Wrappers
 SEXP hello_wrapper(void){
-  return Rf_ScalarString(Rf_mkCharCE(string_from_rust(), CE_UTF8));
+  char* hello_rust = string_from_rust();
+  SEXP hello_world_string = PROTECT(Rf_mkCharCE(hello_rust, CE_UTF8));
+  free_string_from_rust(hello_rust);
+  UNPROTECT(1);
+  return Rf_ScalarString(hello_world_string);
 }
 
 SEXP random_wrapper(void){