runtime_init_memory.js

/**
 * @license
 * Copyright 2019 The Emscripten Authors
 * SPDX-License-Identifier: MIT
 */

// Create the wasm memory. (Note: this only applies if IMPORTED_MEMORY is defined)
#if !IMPORTED_MEMORY
{{{ throw "this file should not be be included when IMPORTED_MEMORY is set"; }}}
#endif

{{{ makeModuleReceiveWithVar('INITIAL_MEMORY', undefined, INITIAL_MEMORY) }}}

assert(INITIAL_MEMORY >= {{{STACK_SIZE}}}, 'INITIAL_MEMORY should be larger than STACK_SIZE, was ' + INITIAL_MEMORY + '! (STACK_SIZE=' + {{{STACK_SIZE}}} + ')');

// check for full engine support (use string 'subarray' to avoid closure compiler confusion)

#if PTHREADS
if (ENVIRONMENT_IS_PTHREAD) {
  wasmMemory = Module['wasmMemory'];
} else {
#endif // PTHREADS

#if expectToReceiveOnModule('wasmMemory')
  if (Module['wasmMemory']) {
    wasmMemory = Module['wasmMemory'];
  } else
#endif
  {
    wasmMemory = new WebAssembly.Memory({
      'initial': INITIAL_MEMORY / {{{ WASM_PAGE_SIZE }}},
#if ALLOW_MEMORY_GROWTH
      // In theory we should not need to emit the maximum if we want "unlimited"
      // or 4GB of memory, but VMs error on that atm, see
      // https://github.com/emscripten-core/emscripten/issues/14130
      // And in the pthreads case we definitely need to emit a maximum. So
      // always emit one.
      'maximum': {{{ MAXIMUM_MEMORY }}} / {{{ WASM_PAGE_SIZE }}}
#else
      'maximum': INITIAL_MEMORY / {{{ WASM_PAGE_SIZE }}}
#endif // ALLOW_MEMORY_GROWTH
#if SHARED_MEMORY
      ,
      'shared': true
#endif
    });
#if SHARED_MEMORY
    if (!(wasmMemory.buffer instanceof SharedArrayBuffer)) {
      err('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');
      if (ENVIRONMENT_IS_NODE) {
        err('(on node you may need: --experimental-wasm-threads --experimental-wasm-bulk-memory and/or recent version)');
      }
      throw Error('bad memory');
    }
#endif
  }

#if PTHREADS
}
#endif

updateMemoryViews();

// If the user provides an incorrect length, just use that length instead rather than providing the user to
// specifically provide the memory length with Module['INITIAL_MEMORY'].
INITIAL_MEMORY = wasmMemory.buffer.byteLength;
#if ASSERTIONS
assert(INITIAL_MEMORY % {{{ WASM_PAGE_SIZE }}} === 0);
#endif