Add compile-time refcount bug hunt build mode (#952)

Reintroduce JSValueConst and add a JS_CHECK_JSVALUE build mode that
catches reference counting bugs by making JSValue and JSValueConst
different types.

The *vast* majority of this commit is rote work to make our own sources
compile cleanly in said mode.

Refs: #944

Author: bnoordhuis

.github/workflows/ci.yml

@@ -592,3 +592,11 @@ jobs:
       - name: test
         run: |
           make test RUN262=$RUNNER_TEMP/run-test262
+
+  jscheck:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: jscheck
+        run: |
+          make jscheck

Makefile

@@ -90,6 +90,23 @@ distclean:
 stats: $(QJS)
 	$(QJS) -qd
 
+jscheck: CFLAGS=-I. -D_GNU_SOURCE -DJS_CHECK_JSVALUE -Wall -Werror -fsyntax-only -c -o /dev/null
+jscheck:
+	$(CC) $(CFLAGS) api-test.c
+	$(CC) $(CFLAGS) ctest.c
+	$(CC) $(CFLAGS) fuzz.c
+	$(CC) $(CFLAGS) gen/function_source.c
+	$(CC) $(CFLAGS) gen/hello.c
+	$(CC) $(CFLAGS) gen/hello_module.c
+	$(CC) $(CFLAGS) gen/repl.c
+	$(CC) $(CFLAGS) gen/standalone.c
+	$(CC) $(CFLAGS) gen/test_fib.c
+	$(CC) $(CFLAGS) qjs.c
+	$(CC) $(CFLAGS) qjsc.c
+	$(CC) $(CFLAGS) quickjs-libc.c
+	$(CC) $(CFLAGS) quickjs.c
+	$(CC) $(CFLAGS) run-test262.c
+
 # effectively .PHONY because it doesn't generate output
 ctest: CFLAGS=-std=c11 -fsyntax-only -Wall -Wextra -Werror -pedantic
 ctest: ctest.c quickjs.h
@@ -126,4 +143,4 @@ unicode_gen: $(BUILD_DIR)
 libunicode-table.h: unicode_gen
 	$(BUILD_DIR)/unicode_gen unicode $@
 
-.PHONY: all amalgam ctest cxxtest debug fuzz install clean codegen distclean stats test test262 test262-update test262-check microbench unicode_gen $(QJS) $(QJSC)
+.PHONY: all amalgam ctest cxxtest debug fuzz jscheck install clean codegen distclean stats test test262 test262-update test262-check microbench unicode_gen $(QJS) $(QJSC)

api-test.c

@@ -74,7 +74,8 @@ static void async_call(void)
     JS_FreeRuntime(rt);
 }
 
-static JSValue save_value(JSContext *ctx, JSValue this_val, int argc, JSValue *argv)
+static JSValue save_value(JSContext *ctx, JSValueConst this_val,
+                          int argc, JSValueConst *argv)
 {
     assert(argc == 1);
     JSValue *p = (JSValue *)JS_GetContextOpaque(ctx);

qjs.c

@@ -199,14 +199,14 @@ static int64_t parse_limit(const char *arg) {
     return (int64_t)(d * unit);
 }
 
-static JSValue js_gc(JSContext *ctx, JSValue this_val,
-                     int argc, JSValue *argv)
+static JSValue js_gc(JSContext *ctx, JSValueConst this_val,
+                     int argc, JSValueConst *argv)
 {
     JS_RunGC(JS_GetRuntime(ctx));
     return JS_UNDEFINED;
 }
 
-static JSValue js_navigator_get_userAgent(JSContext *ctx, JSValue this_val)
+static JSValue js_navigator_get_userAgent(JSContext *ctx, JSValueConst this_val)
 {
     char version[32];
     snprintf(version, sizeof(version), "quickjs-ng/%s", JS_GetVersion());
@@ -667,7 +667,7 @@ int main(int argc, char **argv)
             args[0] = JS_NewString(ctx, compile_file);
             args[1] = JS_NewString(ctx, out);
             args[2] = JS_NewString(ctx, exe != NULL ? exe : argv[0]);
-            ret = JS_Call(ctx, func, JS_UNDEFINED, countof(args), args);
+            ret = JS_Call(ctx, func, JS_UNDEFINED, 3, (JSValueConst *)args);
             JS_FreeValue(ctx, func);
             JS_FreeValue(ctx, args[0]);
             JS_FreeValue(ctx, args[1]);