From 071c76f250f5a6fd964def342417af653132937b Mon Sep 17 00:00:00 2001
From: Nathan Voglsam <nathan.p.voglsam@gmail.com>
Date: Fri, 5 Dec 2025 16:39:20 +1100
Subject: [PATCH 1/2] Add 'JS_FreeCStringRT'

---
 quickjs.c | 8 ++++++++
 quickjs.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/quickjs.c b/quickjs.c
index 5a15e00eb..e4a98cecf 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -4360,6 +4360,14 @@ void JS_FreeCString(JSContext *ctx, const char *ptr)
     JS_FreeValue(ctx, JS_MKPTR(JS_TAG_STRING, (JSString *)ptr - 1));
 }
 
+void JS_FreeCStringRT(JSRuntime *rt, const char *ptr)
+{
+    if (!ptr)
+        return;
+    /* purposely removing constness */
+    JS_FreeValueRT(rt, JS_MKPTR(JS_TAG_STRING, (JSString *)ptr - 1));
+}
+
 static int memcmp16_8(const uint16_t *src1, const uint8_t *src2, int len)
 {
     int c, i;
diff --git a/quickjs.h b/quickjs.h
index b1ab008d9..effc62db5 100644
--- a/quickjs.h
+++ b/quickjs.h
@@ -820,6 +820,7 @@ static inline const char *JS_ToCString(JSContext *ctx, JSValueConst val1)
     return JS_ToCStringLen2(ctx, NULL, val1, 0);
 }
 JS_EXTERN void JS_FreeCString(JSContext *ctx, const char *ptr);
+JS_EXTERN void JS_FreeCStringRT(JSRuntime *rt, const char *ptr);
 
 JS_EXTERN JSValue JS_NewObjectProtoClass(JSContext *ctx, JSValueConst proto,
                                          JSClassID class_id);

From 9c55a7ff970697f904a5e820167564fb40e49cf3 Mon Sep 17 00:00:00 2001
From: Nathan Voglsam <nathan.p.voglsam@gmail.com>
Date: Sun, 7 Dec 2025 13:46:24 +1100
Subject: [PATCH 2/2] Add test for JS_FreeCStringRT

---
 api-test.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/api-test.c b/api-test.c
index 28ff361a6..c6e9d2133 100644
--- a/api-test.c
+++ b/api-test.c
@@ -382,6 +382,44 @@ static void module_serde(void)
     JS_FreeRuntime(rt);
 }
 
+static void runtime_cstring_free(void)
+{
+    JSRuntime *rt = JS_NewRuntime();
+    JSContext *ctx = JS_NewContext(rt);
+    // string -> cstring + JS_FreeCStringRT
+    {
+        JSValue ret = eval(ctx, "\"testStringPleaseIgnore\"");
+        assert(JS_IsString(ret));
+        const char *s = JS_ToCString(ctx, ret);
+        assert(s);
+        assert(strcmp(s, "testStringPleaseIgnore") == 0);
+        JS_FreeCStringRT(rt, s);
+        JS_FreeValue(ctx, ret);
+    }
+    // string -> cstring + JS_FreeCStringRT, destroying the source value first
+    {
+        JSValue ret = eval(ctx, "\"testStringPleaseIgnore\"");
+        assert(JS_IsString(ret));
+        const char *s = JS_ToCString(ctx, ret);
+        assert(s);
+        JS_FreeValue(ctx, ret);
+        assert(strcmp(s, "testStringPleaseIgnore") == 0);
+        JS_FreeCStringRT(rt, s);
+    }
+    // number -> cstring + JS_FreeCStringRT
+    {
+        JSValue ret = eval(ctx, "123987");
+        assert(JS_IsNumber(ret));
+        const char *s = JS_ToCString(ctx, ret);
+        assert(s);
+        assert(strcmp(s, "123987") == 0);
+        JS_FreeCStringRT(rt, s);
+        JS_FreeValue(ctx, ret);
+    }
+    JS_FreeContext(ctx);
+    JS_FreeRuntime(rt);
+}
+
 static void two_byte_string(void)
 {
     JSRuntime *rt = JS_NewRuntime();
@@ -804,6 +842,7 @@ int main(void)
     raw_context_global_var();
     is_array();
     module_serde();
+    runtime_cstring_free();
     two_byte_string();
     weak_map_gc_check();
     promise_hook();