Improve errors on mismatched #endif/#else in JS library files. NFC (e…

…mscripten-core#22344)
juj · Aug 8, 2024 · 08f5c0f · 08f5c0f
1 parent c26eb85
commit 08f5c0f
Show file tree

Hide file tree

Showing 2 changed files with 22 additions and 2 deletions.
diff --git a/src/parseTools.mjs b/src/parseTools.mjs
@@ -132,15 +132,19 @@ export function preprocess(filename) {
             }
           }
         } else if (first === '#else') {
-          assert(showStack.length > 0);
+          if (showStack.length == 0) {
+            error(`${filename}:${i + 1}: #else without matching #if`);
+          }
           const curr = showStack.pop();
           if (curr == IGNORE) {
             showStack.push(SHOW);
           } else {
             showStack.push(IGNORE);
           }
         } else if (first === '#endif') {
-          assert(showStack.length > 0);
+          if (showStack.length == 0) {
+            error(`${filename}:${i + 1}: #endif without matching #if`);
+          }
           showStack.pop();
         } else if (first === '#warning') {
           if (showCurrentLine()) {

diff --git a/test/test_other.py b/test/test_other.py
@@ -4522,6 +4522,22 @@ def test_js_lib_using_asm_lib(self):
 ''')
     self.do_runf('src.c', 'c calling: 14\n', emcc_args=['--js-library', 'lib.js'])
 
+  def test_js_lib_errors(self):
+    create_file('lib.js', '''\
+// This is a library file
+#endif // line 2
+''')
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '--js-library', 'lib.js'])
+    self.assertContained('lib.js:2: #endif without matching #if', err)
+
+    create_file('lib.js', '''\
+// This is a library file
+
+#else // line 3
+''')
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '--js-library', 'lib.js'])
+    self.assertContained('lib.js:3: #else without matching #if', err)
+
   def test_js_internal_deps(self):
     create_file('lib.js', r'''
 addToLibrary({