Change definition of true and false macros to be js friendly (#24255)

Author: hoodmane

system/include/emscripten/em_asm.h

@@ -285,4 +285,20 @@ const char __em_asm_sig_builder<__em_asm_type_tuple<Args...> >::buffer[] = { __e
 #define EM_ASM_INT_V(code) EM_ASM_INT(code)
 #define EM_ASM_DOUBLE_V(code) EM_ASM_DOUBLE(code)
 
+
+// Normally macros like `true` and `false` are not expanded inside
+// of `EM_JS` or `EM_ASM` blocks.  However, in the case then an
+// additional macro later is added these will be expanded and we want
+// to make sure the resulting expansion doesn't break the expectations
+// of JS code
+#if defined(true) && defined(false)
+#undef true
+#undef false
+// These work for both C and javascript.
+// In C !!0 ==> 0 and in javascript !!0 ==> false
+// In C !!1 ==> 1 and in javascript !!1 ==> true
+#define true (!!1)
+#define false (!!0)
+#endif
+
 #endif // !defined(__cplusplus) && defined(__STRICT_ANSI__)

system/include/emscripten/em_js.h

@@ -72,3 +72,19 @@
 
 #define EM_ASYNC_JS(ret, name, params, ...) _EM_JS(ret, name, __asyncjs__##name, params,          \
   "{ return Asyncify.handleAsync(async () => " #__VA_ARGS__ "); }")
+
+
+// Normally macros like `true` and `false` are not expanded inside
+// of `EM_JS` or `EM_ASM` blocks.  However, in the case then an
+// additional macro later is added these will be expanded and we want
+// to make sure the resulting expansion doesn't break the expectations
+// of JS code
+#if defined(true) && defined(false)
+#undef true
+#undef false
+// These work for both C and javascript.
+// In C !!0 ==> 0 and in javascript !!0 ==> false
+// In C !!1 ==> 1 and in javascript !!1 ==> true
+#define true (!!1)
+#define false (!!0)
+#endif

test/test_other.py

@@ -16062,3 +16062,28 @@ def test_getentropy_d8(self):
     self.do_runf('main.c', msg, assert_returncode=1)
     self.v8_args += ['--enable-os-system']
     self.do_runf('main.c')
+
+  def test_em_js_bool_macro_expansion(self):
+    # Normally macros like `true` and `false` are not expanded inside
+    # of `EM_JS` or `EM_ASM` blocks.  However, in the case then an
+    # additional macro later is added these will be expanded and we want
+    # to make sure the resulting expansion doesn't break the expectations
+    # of JS code.
+    create_file('main.c', '''
+      #include <emscripten.h>
+
+      #define EM_JS_MACROS(ret, func_name, args, body...)    \
+        EM_JS(ret, func_name, args, body)
+
+      EM_JS_MACROS(void, check_bool_type, (void), {
+        if (typeof true !== "boolean") {
+          throw new Error("typeof true is " + typeof true + " not boolean");
+        }
+      })
+
+      int main() {
+        check_bool_type();
+        return 0;
+      }
+    ''')
+    self.do_runf('main.c')