Improve testing of liblegacy.js. NFC (#25515)

We had some testing for `LEGACY_RUNTIME` but not explicitly for the
usage of symbols in `liblegacy.js` which are two slightly different
things.

Author: sbc100

src/lib/liblegacy.js

@@ -2,6 +2,16 @@
  * @license
  * Copyright 2010 The Emscripten Authors
  * SPDX-License-Identifier: MIT
+ *
+ * Legacy library symbols that are no longer used by emscripten itself but
+ * could have external users.
+ *
+ * Symbols in this file are not available in `-sSTRICT` mode.
+ *
+ * Any usage of symbols in this file will result in a `-Wdeprecated` warning.
+ *
+ * Symbol in this file should be removed after "enough time" has passed such
+ * that all external users have been able to transision away.
  */
 
 legacyFuncs = {
@@ -73,8 +83,10 @@ legacyFuncs = {
     if (!dontAddNull) {{{ makeSetValue('buffer', 0, 0, 'i8') }}};
   },
 
-  $allocateUTF8: '$stringToNewUTF8',
-  $allocateUTF8OnStack: '$stringToUTF8OnStack',
+  $allocateUTF8__deps: ['$stringToNewUTF8'],
+  $allocateUTF8: (...args) => stringToNewUTF8(...args),
+  $allocateUTF8OnStack__deps: ['$stringToUTF8OnStack'],
+  $allocateUTF8OnStack: (...args) => stringToUTF8OnStack(...args),
 
 #if LINK_AS_CXX
   $demangle__deps: ['$withStackSave', '__cxa_demangle', 'free', '$stringToUTF8OnStack'],
@@ -130,8 +142,8 @@ legacyFuncs = {
 if (WARN_DEPRECATED && !INCLUDE_FULL_LIBRARY) {
   for (const name of Object.keys(legacyFuncs)) {
     if (!isDecorator(name)) {
-      depsKey = `${name}__deps`;
-      legacyFuncs[depsKey] = legacyFuncs[depsKey] || [];
+      const depsKey = `${name}__deps`;
+      legacyFuncs[depsKey] ??= []
       legacyFuncs[depsKey].push(() => {
         warn(`JS library symbol '${name}' is deprecated. Please open a bug if you have a continuing need for this symbol [-Wdeprecated]`);
       });

test/codesize/test_codesize_hello_O0.json

@@ -1,10 +1,10 @@
 {
   "a.out.js": 23198,
-  "a.out.js.gz": 8524,
+  "a.out.js.gz": 8525,
   "a.out.nodebug.wasm": 15127,
   "a.out.nodebug.wasm.gz": 7450,
   "total": 38325,
-  "total_gz": 15974,
+  "total_gz": 15975,
   "sent": [
     "fd_write"
   ],

test/codesize/test_unoptimized_code_size.json

@@ -1,6 +1,6 @@
 {
   "hello_world.js": 55508,
-  "hello_world.js.gz": 17498,
+  "hello_world.js.gz": 17499,
   "hello_world.wasm": 15127,
   "hello_world.wasm.gz": 7450,
   "no_asserts.js": 26614,
@@ -12,5 +12,5 @@
   "strict.wasm": 15127,
   "strict.wasm.gz": 7447,
   "total": 178126,
-  "total_gz": 64105
+  "total_gz": 64106
 }

test/other/test_legacy_runtime.c

@@ -3,7 +3,7 @@
 
 int main () {
   intptr_t addr = EM_ASM_INT({
-     return allocate(intArrayFromString("hello from js"), ALLOC_NORMAL);
+     return stringToNewUTF8("hello from js");
   });
   printf("%s\n", (char*)addr);
   return 0;

test/test_other.py

@@ -13944,30 +13944,33 @@ def test_stdint_limits(self):
 
   def test_legacy_runtime(self):
     self.set_setting('EXPORTED_FUNCTIONS', ['_malloc', '_main'])
-    self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', ['$intArrayFromString', '$ALLOC_NORMAL'])
 
-    # By default `LEGACY_RUNTIME` is disabled and `allocate` is not available.
-    self.set_setting('EXPORTED_RUNTIME_METHODS', ['ALLOC_NORMAL'])
+    # By default `LEGACY_RUNTIME` is disabled and `stringToNewUTF8` is not available.
     self.cflags += ['-Wno-deprecated']
     self.do_runf('other/test_legacy_runtime.c',
-                 '`allocate` is a library symbol and not included by default; add it to your library.js __deps or to DEFAULT_LIBRARY_FUNCS_TO_INCLUDE on the command line',
+                 '`stringToNewUTF8` is a library symbol and not included by default; add it to your library.js __deps or to DEFAULT_LIBRARY_FUNCS_TO_INCLUDE on the command line',
                  assert_returncode=NON_ZERO)
 
     # When we enable `LEGACY_RUNTIME`, `allocate` should be available.
-    self.set_setting('LEGACY_RUNTIME', 1)
-    self.do_runf('other/test_legacy_runtime.c')
+    self.do_runf('other/test_legacy_runtime.c', 'hello from js', cflags=['-sLEGACY_RUNTIME'])
 
     # Adding it to EXPORTED_RUNTIME_METHODS should also make it available.
-    self.clear_setting('LEGACY_RUNTIME')
-    self.set_setting('EXPORTED_RUNTIME_METHODS', ['allocate'])
-    self.do_runf('other/test_legacy_runtime.c', 'hello from js')
+    self.do_runf('other/test_legacy_runtime.c', 'hello from js', cflags=['-sEXPORTED_RUNTIME_METHODS=stringToNewUTF8'])
 
-    # In strict mode the library function is not even available, so we get a build time error
-    self.set_setting('STRICT')
-    self.clear_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE')
-    for opt in ('-O0', '-O3'):
-      err = self.expect_fail([EMCC, test_file('other/test_legacy_runtime.c'), opt] + self.get_cflags())
-      self.assertContained('undefined exported symbol: "allocate" in EXPORTED_RUNTIME_METHODS', err)
+  @parameterized({
+    '': (['-O0'],),
+    'O3': (['-O3'],),
+  })
+  def test_legacy_jslib(self, args):
+    # Warn about usage of legacy library function
+    err = self.run_process([EMCC, test_file('hello_world.c'), '-sEXPORTED_RUNTIME_METHODS=allocateUTF8'] + args, stderr=PIPE).stderr
+    self.assertContained("warning: JS library symbol '$allocateUTF8' is deprecated. Please open a bug if you have a continuing need for this symbol", err)
+
+    self.assertContained('emcc: warning: warnings in JS library compilation [-Wjs-compiler]', err)
+
+    # In strict mode legacy library functions are not available, so we get a build time error
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-sEXPORTED_RUNTIME_METHODS=allocateUTF8', '-sSTRICT'] + args)
+    self.assertContained('undefined exported symbol: "allocateUTF8" in EXPORTED_RUNTIME_METHODS', err)
 
   def test_fetch_settings(self):
     create_file('pre.js', '''