Undo assertion on STANDALONE_WASM not working with memory growth

emcc.py

@@ -1786,8 +1786,6 @@ def check_human_readable_list(items):
         exit_with_error('STANDALONE_WASM does not support pthreads yet')
       if shared.Settings.SIMD:
         exit_with_error('STANDALONE_WASM does not support simd yet')
-      if shared.Settings.ALLOW_MEMORY_GROWTH:
-        exit_with_error('STANDALONE_WASM does not support memory growth yet')
       # the wasm must be runnable without the JS, so there cannot be anything that
       # requires JS legalization
       shared.Settings.LEGALIZE_JS_FFI = 0

site/source/docs/api_reference/emscripten.h.rst

@@ -1363,3 +1363,20 @@ Functions
     This function requires Asyncify - it relies on that option to spill the
     local state all the way up the stack. As a result, it will add overhead
     to your program.
+
+ABI functions
+=============
+
+The following functions are not declared in ``emscripten.h``, but are used
+internally in our system libraries. You may care about them if you replace the
+Emscripten runtime JS code, or run Emscripten binaries in your own runtime.
+
+
+.. c:function:: void emscripten_notify_memory_growth(i32 index)
+
+    Called when memory has grown. In a JS runtime, this is used to know when
+    to update the JS views on the wasm memory, which otherwise we would need
+    to constantly check for after any wasm code runs. See
+    `this wasi discussion <https://github.com/WebAssembly/WASI/issues/82>`_.
+
+    :param i32 index: Which memory has grown.

src/library.js

@@ -642,6 +642,17 @@ LibraryManager.library = {
 #endif // ALLOW_MEMORY_GROWTH
   },
 
+  // Called after wasm grows memory. At that time we need to update the views.
+  // Without this notification, we'd need to check the buffer in JS every time
+  // we return from any wasm, which adds overhead. See
+  // https://github.com/WebAssembly/WASI/issues/82
+  emscripten_notify_memory_growth: function(memoryIndex) {
+#if ASSERTIONS
+    assert(memoryIndex == 0);
+#endif
+    updateGlobalBufferAndViews(wasmMemory.buffer);
+  },
+
   system__deps: ['__setErrNo'],
   system: function(command) {
     // int system(const char *command);

src/preamble.js

@@ -925,7 +925,8 @@ function createWasm() {
     // In pure wasm mode the memory is created in the wasm (not imported), and
     // then exported.
     // TODO: do not create a Memory earlier in JS
-    updateGlobalBufferAndViews(exports['memory'].buffer);
+    wasmMemory = exports['memory'];
+    updateGlobalBufferAndViews(wasmMemory.buffer);
 #if ASSERTIONS
     writeStackCookie();
 #endif

system/lib/standalone_wasm.c

@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include <assert.h>
 #include <emscripten.h>
 #include <errno.h>
 #include <stdio.h>
@@ -70,11 +71,22 @@ void *emscripten_memcpy_big(void *restrict dest, const void *restrict src, size_
 
 static const int WASM_PAGE_SIZE = 65536;
 
-// Note that this does not support memory growth in JS because we don't update the JS
-// heaps. Wasm and wasi lack a good API for that.
+extern void emscripten_notify_memory_growth(size_t memory_index);
+
 int emscripten_resize_heap(size_t size) {
-  size_t result = __builtin_wasm_memory_grow(0, (size + WASM_PAGE_SIZE - 1) / WASM_PAGE_SIZE);
-  return result != (size_t)-1;
+#ifdef __EMSCRIPTEN_MEMORY_GROWTH__
+  size_t old_size = __builtin_wasm_memory_size(0) * WASM_PAGE_SIZE;
+  assert(old_size < size);
+  ssize_t diff = (size - old_size + WASM_PAGE_SIZE - 1) / WASM_PAGE_SIZE;
+  size_t result = __builtin_wasm_memory_grow(0, diff);
+  if (result != (size_t)-1) {
+
+   // Success, update JS (see https://github.com/WebAssembly/WASI/issues/82)
+    emscripten_notify_memory_growth(0);
+    return 1;
+  }
+#endif
+  return 0;
 }
 
 // C++ ABI

tests/other/metadce/hello_world_fastcomp_O3_MAIN_MODULE.sent

@@ -911,6 +911,7 @@ _emscripten_log_js
 _emscripten_longjmp
 _emscripten_main_browser_thread_id
 _emscripten_memcpy_big
+_emscripten_notify_memory_growth
 _emscripten_pause_main_loop
 _emscripten_pc_get_column
 _emscripten_pc_get_file

tests/test_core.py

@@ -127,6 +127,27 @@ def decorated(self):
   return decorated
 
 
+# Similar to also_with_standalone_wasm, but suitable for tests that cannot
+# run in a wasm VM yet, as they are not 100% standalone. We can still
+# run them with the JS code though.
+def also_with_impure_standalone_wasm(func):
+  def decorated(self):
+    func(self)
+    # Standalone mode is only supported in the wasm backend, and not in all
+    # modes there.
+    if self.is_wasm_backend() and self.get_setting('WASM') and not self.get_setting('SAFE_STACK'):
+      print('standalone (impure; no wasm runtimes)')
+      self.set_setting('STANDALONE_WASM', 1)
+      wasm_engines = shared.WASM_ENGINES
+      try:
+        shared.WASM_ENGINES = []
+        func(self)
+      finally:
+        shared.WASM_ENGINES = wasm_engines
+
+  return decorated
+
+
 # A simple check whether the compiler arguments cause optimization.
 def is_optimizing(args):
   return '-O' in str(args) and '-O0' not in args
@@ -1929,6 +1950,7 @@ def test_memorygrowth_3(self):
     self.emcc_args += ['-s', 'ALLOW_MEMORY_GROWTH=0', '-s', 'ABORTING_MALLOC=0', '-s', 'SAFE_HEAP']
     self.do_run_in_out_file_test('tests', 'core', 'test_memorygrowth_3')
 
+  @also_with_impure_standalone_wasm
   def test_memorygrowth_wasm_mem_max(self):
     if self.has_changed_setting('ALLOW_MEMORY_GROWTH'):
       self.skipTest('test needs to modify memory growth')

tests/test_other.py

@@ -8104,7 +8104,7 @@ def test_binaryen_metadce_hello(self, *args):
                       4, [],        [],           8,   0,    0,  0), # noqa; totally empty!
     # we don't metadce with linkable code! other modules may want stuff
     # don't compare the # of functions in a main module, which changes a lot
-    'main_module_1': (['-O3', '-s', 'MAIN_MODULE=1'], 1603, [], [], 226403, None, 107, None), # noqa
+    'main_module_1': (['-O3', '-s', 'MAIN_MODULE=1'], 1604, [], [], 226403, None, 107, None), # noqa
     'main_module_2': (['-O3', '-s', 'MAIN_MODULE=2'],   13, [], [],  10017,   13,   9,   20), # noqa
   })
   @no_wasm_backend()

tools/shared.py

@@ -543,7 +543,7 @@ def get_emscripten_version(path):
 # change, increment EMSCRIPTEN_ABI_MINOR if EMSCRIPTEN_ABI_MAJOR == 0
 # or the ABI change is backwards compatible, otherwise increment
 # EMSCRIPTEN_ABI_MAJOR and set EMSCRIPTEN_ABI_MINOR = 0.
-(EMSCRIPTEN_ABI_MAJOR, EMSCRIPTEN_ABI_MINOR) = (0, 16)
+(EMSCRIPTEN_ABI_MAJOR, EMSCRIPTEN_ABI_MINOR) = (0, 17)
 
 
 def generate_sanity():

tools/system_libs.py

@@ -1185,6 +1185,33 @@ class libstandalonewasm(MuslInternalLibrary):
   cflags = ['-Os']
   src_dir = ['system', 'lib']
 
+  def __init__(self, **kwargs):
+    self.is_mem_grow = kwargs.pop('is_mem_grow')
+    super(libstandalonewasm, self).__init__(**kwargs)
+
+  def get_base_name(self):
+    name = super(libstandalonewasm, self).get_base_name()
+    if self.is_mem_grow:
+      name += '-memgrow'
+    return name
+
+  def get_cflags(self):
+    cflags = super(libstandalonewasm, self).get_cflags()
+    if self.is_mem_grow:
+      cflags += ['-D__EMSCRIPTEN_MEMORY_GROWTH__=1']
+    return cflags
+
+  @classmethod
+  def vary_on(cls):
+    return super(libstandalonewasm, cls).vary_on() + ['is_mem_grow']
+
+  @classmethod
+  def get_default_variation(cls, **kwargs):
+    return super(libstandalonewasm, cls).get_default_variation(
+      is_mem_grow=shared.Settings.ALLOW_MEMORY_GROWTH,
+      **kwargs
+    )
+
   def get_files(self):
     base_files = files_in_path(
         path_components=['system', 'lib'],