Handle JS compiler warning in python (#17365)

This makes `-Werror` work for JS compiler warnings just like it does
for others.

Also, consistently use `err` over `out` when reporting warnings.

Also, avoid adding the `warning;` prefix when calling `warn` in the
JS compiler, since its inject automatically.

Author: sbc100

ChangeLog.md

@@ -20,6 +20,10 @@ See docs/process.md for more on how version tagging works.
 
 3.1.16
 ------
+- Warnings generated by the JS compiler (compiler.js) are now propagated back
+  to the emcc compiler driver which means that `-Werror` builds will now fail
+  in the presence of JS compiler warnings.  As usual `-Wno-js-compiler` and
+  `-Wno-error=js-compiler)` can be used to control these warnings. (#17365)
 - When JS library functions are included as part of `EXPORTED_RUNTIME_METHODS`
   it is no longer necessary to also add them to
   `DEFAULT_LIBRARY_FUNCS_TO_INCLUDE`.  This change allows us to transition

emscripten.py

@@ -354,6 +354,9 @@ def emscript(in_wasm, out_wasm, outfile_js, memfile):
 
   forwarded_json = json.loads(forwarded_data)
 
+  if forwarded_json['warnings']:
+    diagnostics.warning('js-compiler', 'warnings in JS library compilation')
+
   pre, post = glue.split('// EMSCRIPTEN_END_FUNCS')
 
   if settings.ASSERTIONS:

src/jsifier.js

@@ -530,6 +530,7 @@ function ${name}(${args}) {
 
     print('\n//FORWARDED_DATA:' + JSON.stringify({
       libraryFunctions: libraryFunctions,
+      warnings: warnings,
       ATINITS: ATINITS.join('\n'),
       ATMAINS: ATMAINS.join('\n'),
       ATEXITS: ATEXITS.join('\n'),

src/library_browser.js

@@ -112,12 +112,12 @@ var LibraryBrowser = {
         Browser.hasBlobConstructor = true;
       } catch(e) {
         Browser.hasBlobConstructor = false;
-        out("warning: no blob constructor, cannot create blobs with mimetypes");
+        err("warning: no blob constructor, cannot create blobs with mimetypes");
       }
-      Browser.BlobBuilder = typeof MozBlobBuilder != "undefined" ? MozBlobBuilder : (typeof WebKitBlobBuilder != "undefined" ? WebKitBlobBuilder : (!Browser.hasBlobConstructor ? out("warning: no BlobBuilder") : null));
+      Browser.BlobBuilder = typeof MozBlobBuilder != "undefined" ? MozBlobBuilder : (typeof WebKitBlobBuilder != "undefined" ? WebKitBlobBuilder : (!Browser.hasBlobConstructor ? err("warning: no BlobBuilder") : null));
       Browser.URLObject = typeof window != "undefined" ? (window.URL ? window.URL : window.webkitURL) : undefined;
       if (!Module.noImageDecoding && typeof Browser.URLObject == 'undefined') {
-        out("warning: Browser does not support creating object URLs. Built-in browser image decoding will not be available.");
+        err("warning: Browser does not support creating object URLs. Built-in browser image decoding will not be available.");
         Module.noImageDecoding = true;
       }
 
@@ -207,7 +207,7 @@ var LibraryBrowser = {
           audio.addEventListener('canplaythrough', function() { finish(audio) }, false); // use addEventListener due to chromium bug 124926
           audio.onerror = function audio_onerror(event) {
             if (done) return;
-            out('warning: browser could not fully decode audio ' + name + ', trying slower base64 approach');
+            err('warning: browser could not fully decode audio ' + name + ', trying slower base64 approach');
             function encode64(data) {
               var BASE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
               var PAD = '=';

src/library_sdl.js

@@ -2584,7 +2584,7 @@ var LibrarySDL = {
           var curtime = SDL.audioContext['currentTime'];
 #if ASSERTIONS
           if (curtime > SDL.audio.nextPlayTime && SDL.audio.nextPlayTime != 0) {
-            out('warning: Audio callback had starved sending audio by ' + (curtime - SDL.audio.nextPlayTime) + ' seconds.');
+            err('warning: Audio callback had starved sending audio by ' + (curtime - SDL.audio.nextPlayTime) + ' seconds.');
           }
 #endif
           // Don't ever start buffer playbacks earlier from current time than a given constant 'SDL.audio.bufferingDelay', since a browser

src/modules.js

@@ -531,7 +531,7 @@ function exportRuntime() {
     const runtimeElementsSet = new Set(runtimeElements);
     for (const name of EXPORTED_RUNTIME_METHODS_SET) {
       if (!runtimeElementsSet.has(name)) {
-        printErr(`warning: invalid item in EXPORTED_RUNTIME_METHODS: ${name}`);
+        warn(`invalid item in EXPORTED_RUNTIME_METHODS: ${name}`);
       }
     }
   }

src/parseTools.js

@@ -80,7 +80,7 @@ function preprocess(text, filenameHint) {
             const first = trimmed.split(' ', 1)[0];
             if (first == '#if' || first == '#ifdef' || first == '#elif') {
               if (first == '#ifdef') {
-                warn('warning: use of #ifdef in js library.  Use #if instead.');
+                warn('use of #ifdef in js library.  Use #if instead.');
               }
               if (first == '#elif') {
                 const curr = showStack.pop();
@@ -825,7 +825,7 @@ function makeDynCall(sig, funcPtr) {
 
 
   if (funcPtr === undefined) {
-    printErr(`warning: ${currentlyParsedFilename}: \
+    warn(`${currentlyParsedFilename}: \
 Legacy use of {{{ makeDynCall("${sig}") }}}(funcPtr, arg1, arg2, ...). \
 Starting from Emscripten 2.0.2 (Aug 31st 2020), syntax for makeDynCall has changed. \
 New syntax is {{{ makeDynCall("${sig}", "funcPtr") }}}(arg1, arg2, ...). \

src/utility.js

@@ -48,7 +48,10 @@ function assert(a, msg) {
   }
 }
 
+global.warnings = false;
+
 function warn(a, msg) {
+  global.warnings = true;
   if (!msg) {
     msg = a;
     a = false;
@@ -67,7 +70,7 @@ function warnOnce(a, msg) {
     if (!warnOnce.msgs) warnOnce.msgs = {};
     if (msg in warnOnce.msgs) return;
     warnOnce.msgs[msg] = true;
-    printErr('warning: ' + msg);
+    warn(msg);
   }
 }
 

tests/test_browser.py

@@ -3307,10 +3307,13 @@ def test_sdl2_mixer_music(self, formats, flags, music_name):
 
   @requires_graphics_hardware
   def test_cocos2d_hello(self):
+    # cocos2d build contains a bunch of warnings about tiff symbols being missing at link time:
+    # e.g. warning: undefined symbol: TIFFClientOpen
     cocos2d_root = os.path.join(ports.Ports.get_build_dir(), 'cocos2d')
     preload_file = os.path.join(cocos2d_root, 'samples', 'HelloCpp', 'Resources') + '@'
     self.btest('cocos2d_hello.cpp', reference='cocos2d_hello.png', reference_slack=1,
                args=['-sUSE_COCOS2D=3', '-sERROR_ON_UNDEFINED_SYMBOLS=0',
+                     '-Wno-js-compiler',
                      '--preload-file', preload_file, '--use-preload-plugins',
                      '-Wno-inconsistent-missing-override'],
                message='You should see Cocos2d logo')

tests/test_webgl_context_attributes_common.c

@@ -289,18 +289,18 @@ extern int webglAlphaSupported(void);
 static void checkContextAttributesSupport() {
   if (!webglAntialiasSupported()) {
     resultAA = true;
-    EM_ASM(out('warning: no antialiasing\n'));
+    EM_ASM(err('warning: no antialiasing\n'));
   }
   if (!webglDepthSupported()) {
     resultDepth = true;
-    EM_ASM(out('warning: no depth\n'));
+    EM_ASM(err('warning: no depth\n'));
   }
   if (!webglStencilSupported()) {
     resultStencil = true;
-    EM_ASM(out('warning: no stencil\n'));
+    EM_ASM(err('warning: no stencil\n'));
   }
   if (!webglAlphaSupported()) {
     resultAlpha = true;
-    EM_ASM(out('warning: no alpha\n'));
+    EM_ASM(err('warning: no alpha\n'));
   }
 }