Allow HEAPX symbols in EXPORT_RUNTIME_METHODS (#21439)

- Factor out updateMemoryViews.
- Enable HEAPXX exports to be specified in EXPORT_RUNTIME_METHODS.
- Add all HEAP symbosl to EXPORT_RUNTIME_METHODS unless in STRICT mode.

Replaces #21407

ChangeLog.md

@@ -21,6 +21,10 @@ See docs/process.md for more on how version tagging works.
 3.1.55 (in development)
 -----------------------
 - Update sdl2-mixer port from 2.6.0 to 2.8.0
+- In `STRICT` mode the `HEAPXX` symbols (such as `HEAP8` and `HEAP32`) are now
+  only exported on demand.  This means that they must be added to
+  `EXPORTED_RUNTIME_METHODS` for them to appear on the `Module` object.  For
+  now, this only effects users of `STRICT` mode. (#21439)
 
 3.1.54 - 02/15/24
 -----------------

src/modules.js

@@ -349,6 +349,10 @@ function exportRuntime() {
   // being exported. how we show the message depends on whether it's
   // a function (almost all of them) or a number.
   function maybeExport(name) {
+    // HEAP objects are exported separately in updateMemoryViews
+    if (name.startsWith('HEAP')) {
+      return;
+    }
     // if requested to be exported, export it
     if (EXPORTED_RUNTIME_METHODS_SET.has(name)) {
       let exported = name;
@@ -385,6 +389,13 @@ function exportRuntime() {
     'abort',
     'wasmMemory',
     'wasmExports',
+    'HEAPF32',
+    'HEAPF64',
+    'HEAP_DATA_VIEW',
+    'HEAP8',  'HEAPU8',
+    'HEAP16', 'HEAPU16',
+    'HEAP32', 'HEAPU32',
+    'HEAP64', 'HEAPU64',
   ];
 
   // These are actually native wasm functions these days but we allow exporting

src/preamble.js

@@ -138,24 +138,7 @@ var HEAP,
 var HEAP_DATA_VIEW;
 #endif
 
-function updateMemoryViews() {
-  var b = wasmMemory.buffer;
-#if SUPPORT_BIG_ENDIAN
-  Module['HEAP_DATA_VIEW'] = HEAP_DATA_VIEW = new DataView(b);
-#endif
-  Module['HEAP8'] = HEAP8 = new Int8Array(b);
-  Module['HEAP16'] = HEAP16 = new Int16Array(b);
-  Module['HEAPU8'] = HEAPU8 = new Uint8Array(b);
-  Module['HEAPU16'] = HEAPU16 = new Uint16Array(b);
-  Module['HEAP32'] = HEAP32 = new Int32Array(b);
-  Module['HEAPU32'] = HEAPU32 = new Uint32Array(b);
-  Module['HEAPF32'] = HEAPF32 = new Float32Array(b);
-  Module['HEAPF64'] = HEAPF64 = new Float64Array(b);
-#if WASM_BIGINT
-  Module['HEAP64'] = HEAP64 = new BigInt64Array(b);
-  Module['HEAPU64'] = HEAPU64 = new BigUint64Array(b);
-#endif
-}
+#include "runtime_shared.js"
 
 #if ASSERTIONS
 assert(!Module['STACK_SIZE'], 'STACK_SIZE can no longer be set at runtime.  Use -sSTACK_SIZE at link time')

src/preamble_minimal.js

@@ -4,17 +4,6 @@
  * SPDX-License-Identifier: MIT
  */
 
-{{{
-  // Helper function to export a symbol on the module object
-  // if requested.
-  globalThis.maybeExport = (x) => MODULARIZE && EXPORT_ALL ? `Module['${x}'] = ` : '';
-  // Export to the AudioWorkletGlobalScope the needed variables to access
-  // the heap. AudioWorkletGlobalScope is unable to access global JS vars
-  // in the compiled main JS file.
-  globalThis.maybeExportIfAudioWorklet = (x) => (MODULARIZE && EXPORT_ALL) || AUDIO_WORKLET ? `Module['${x}'] = ` : '';
-  null;
-}}}
-
 #if SAFE_HEAP
 #include "runtime_safe_heap.js"
 #endif
@@ -65,27 +54,7 @@ var HEAP8, HEAP16, HEAP32, HEAPU8, HEAPU16, HEAPU32, HEAPF32, HEAPF64,
 #endif
   wasmMemory;
 
-function updateMemoryViews() {
-  var b = wasmMemory.buffer;
-#if ASSERTIONS && SHARED_MEMORY
-  assert(b instanceof SharedArrayBuffer, 'requested a shared WebAssembly.Memory but the returned buffer is not a SharedArrayBuffer, indicating that while the browser has SharedArrayBuffer it does not have WebAssembly threads support - you may need to set a flag');
-#endif
-#if SUPPORT_BIG_ENDIAN
-  {{{ maybeExport('HEAP_DATA_VIEW') }}} HEAP_DATA_VIEW = new DataView(b);
-#endif
-  {{{ maybeExport('HEAP8') }}} HEAP8 = new Int8Array(b);
-  {{{ maybeExport('HEAP16') }}} HEAP16 = new Int16Array(b);
-  {{{ maybeExport('HEAPU8') }}} HEAPU8 = new Uint8Array(b);
-  {{{ maybeExport('HEAPU16') }}} HEAPU16 = new Uint16Array(b);
-  {{{ maybeExport('HEAP32') }}} HEAP32 = new Int32Array(b);
-  {{{ maybeExportIfAudioWorklet('HEAPU32') }}} HEAPU32 = new Uint32Array(b);
-  {{{ maybeExportIfAudioWorklet('HEAPF32') }}} HEAPF32 = new Float32Array(b);
-  {{{ maybeExport('HEAPF64') }}} HEAPF64 = new Float64Array(b);
-#if WASM_BIGINT
-  {{{ maybeExport('HEAP64') }}} HEAP64 = new BigInt64Array(b);
-  {{{ maybeExport('HEAPU64') }}} HEAPU64 = new BigUint64Array(b);
-#endif
-}
+#include "runtime_shared.js"
 
 #if IMPORTED_MEMORY
 #if PTHREADS
@@ -116,6 +85,10 @@ else {
 #endif // MODULARIZE
 #endif // PTHREADS
 
+#if ASSERTIONS && SHARED_MEMORY
+assert(wasmMemory.buffer instanceof SharedArrayBuffer, 'requested a shared WebAssembly.Memory but the returned buffer is not a SharedArrayBuffer, indicating that while the browser has SharedArrayBuffer it does not have WebAssembly threads support - you may need to set a flag');
+#endif
+
 updateMemoryViews();
 #endif // IMPORTED_MEMORY
 

src/runtime_shared.js

@@ -0,0 +1,48 @@
+/**
+ * @license
+ * Copyright 2024 The Emscripten Authors
+ * SPDX-License-Identifier: MIT
+ */
+
+{{{
+  // Helper function to export a heap symbol on the module object,
+  // if requested.
+  globalThis.maybeExportHeap = (x) => {
+    // For now, we export all heap object when not building with MINIMAL_RUNTIME
+    let shouldExport = !MINIMAL_RUNTIME && !STRICT;
+    if (!shouldExport) {
+      if (MODULARIZE && EXPORT_ALL) {
+        shouldExport = true;
+      } else if (AUDIO_WORKLET && (x == 'HEAP32' || x == 'HEAPU32')) {
+        // Export to the AudioWorkletGlobalScope the needed variables to access
+        // the heap. AudioWorkletGlobalScope is unable to access global JS vars
+        // in the compiled main JS file.
+        shouldExport = true;
+      } else if (EXPORTED_RUNTIME_METHODS.includes(x)) {
+        shouldExport = true;
+      }
+    }
+
+    return shouldExport ? `Module['${x}'] = ` : '';
+  };
+  null;
+}}}
+
+function updateMemoryViews() {
+  var b = wasmMemory.buffer;
+#if SUPPORT_BIG_ENDIAN
+  {{{ maybeExport('HEAP_DATA_VIEW') }}} HEAP_DATA_VIEW = new DataView(b);
+#endif
+  {{{ maybeExportHeap('HEAP8')   }}}HEAP8 = new Int8Array(b);
+  {{{ maybeExportHeap('HEAP16')  }}}HEAP16 = new Int16Array(b);
+  {{{ maybeExportHeap('HEAPU8')  }}}HEAPU8 = new Uint8Array(b);
+  {{{ maybeExportHeap('HEAPU16') }}}HEAPU16 = new Uint16Array(b);
+  {{{ maybeExportHeap('HEAP32')  }}}HEAP32 = new Int32Array(b);
+  {{{ maybeExportHeap('HEAPU32') }}}HEAPU32 = new Uint32Array(b);
+  {{{ maybeExportHeap('HEAPF32') }}}HEAPF32 = new Float32Array(b);
+  {{{ maybeExportHeap('HEAPF64') }}}HEAPF64 = new Float64Array(b);
+#if WASM_BIGINT
+  {{{ maybeExportHeap('HEAP64')  }}}HEAP64 = new BigInt64Array(b);
+  {{{ maybeExportHeap('HEAPU64') }}}HEAPU64 = new BigUint64Array(b);
+#endif
+}

test/other/metadce/test_metadce_minimal_64.gzsize

@@ -1 +1 @@
-1725
+1685

test/other/metadce/test_metadce_minimal_64.jssize

@@ -1 +1 @@
-3635
+3541

test/other/metadce/test_metadce_minimal_O0.gzsize

@@ -1 +1 @@
-6845
+6858

test/other/metadce/test_metadce_minimal_O0.jssize

@@ -1 +1 @@
-18753
+18751

test/other/metadce/test_metadce_minimal_O1.gzsize

@@ -1 +1 @@
-1827
+1796

test/other/metadce/test_metadce_minimal_O1.jssize

@@ -1 +1 @@
-4419
+4328

test/other/metadce/test_metadce_minimal_O2.gzsize

@@ -1 +1 @@
-1660
+1627

test/other/metadce/test_metadce_minimal_O2.jssize

@@ -1 +1 @@
-3362
+3287

test/other/metadce/test_metadce_minimal_O3.gzsize

@@ -1 +1 @@
-1618
+1591

test/other/metadce/test_metadce_minimal_O3.jssize

@@ -1 +1 @@
-3312
+3237

test/other/metadce/test_metadce_minimal_Os.gzsize

@@ -1 +1 @@
-1618
+1591

test/other/metadce/test_metadce_minimal_Os.jssize

@@ -1 +1 @@
-3312
+3237

test/other/metadce/test_metadce_minimal_Oz-ctors.gzsize

@@ -1 +1 @@
-1610
+1583

test/other/metadce/test_metadce_minimal_Oz-ctors.jssize

@@ -1 +1 @@
-3297
+3222

test/other/metadce/test_metadce_minimal_Oz.gzsize

@@ -1 +1 @@
-1618
+1591

test/other/metadce/test_metadce_minimal_Oz.jssize

@@ -1 +1 @@
-3312
+3237

test/other/metadce/test_metadce_minimal_wasmfs.gzsize

@@ -1 +1 @@
-1618
+1591

test/other/metadce/test_metadce_minimal_wasmfs.jssize

@@ -1 +1 @@
-3312
+3237

test/other/test_unoptimized_code_size.js.size

@@ -1 +1 @@
-58034
+58097

test/other/test_unoptimized_code_size_no_asserts.js.size

@@ -1 +1 @@
-31565
+31628

test/other/test_unoptimized_code_size_strict.js.size

@@ -1 +1 @@
-56997
+57049

tools/link.py

@@ -880,6 +880,18 @@ def phase_linker_setup(options, state, newargs):
     else:
       default_setting('INCOMING_MODULE_JS_API', [])
 
+  if not settings.MINIMAL_RUNTIME and not settings.STRICT:
+    # Export the HEAP object by default, when not running in STRICT mode
+    settings.EXPORTED_RUNTIME_METHODS.extend([
+      'HEAPF32',
+      'HEAPF64',
+      'HEAP_DATA_VIEW',
+      'HEAP8',  'HEAPU8',
+      'HEAP16', 'HEAPU16',
+      'HEAP32', 'HEAPU32',
+      'HEAP64', 'HEAPU64',
+    ])
+
   # Default to TEXTDECODER=2 (always use TextDecoder to decode UTF-8 strings)
   # in -Oz builds, since custom decoder for UTF-8 takes up space.
   # In pthreads enabled builds, TEXTDECODER==2 may not work, see