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Flip the default for LEGALIZE_JS_FFI. NFC #27563

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Merged
sbc100 merged 1 commit into from
Aug 19, 2026
+12 −15
Merged

Flip the default for LEGALIZE_JS_FFI. NFC #27563

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10 changes: 5 additions & 5 deletions site/source/docs/tools_reference/settings_reference.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -2188,14 +2188,14 @@ Default value: false
LEGALIZE_JS_FFI
===============

Whether to legalize the JS FFI interfaces (imports/exports) by wrapping them
to automatically demote i64 to i32 and promote f32 to f64. This is necessary
in order to interface with JavaScript. For non-web/non-JS embeddings,
setting this to 0 may be desirable.
Whether to lower i64 parameters and return values for function
imports/exports. This is done by lowering them to pairs of i32 and should
only be needed on JS engines that do not have Wasm/BigInt integration.
This is automatically enabled when WASM_BIGINT is disabled.

.. note:: This setting is deprecated

Default value: true
Default value: false

.. _use_sdl:

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10 changes: 5 additions & 5 deletions src/settings.js
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Expand Up @@ -1521,13 +1521,13 @@ var EMIT_PRODUCERS_SECTION = false;
// [link]
var EMIT_EMSCRIPTEN_LICENSE = false;

// Whether to legalize the JS FFI interfaces (imports/exports) by wrapping them
// to automatically demote i64 to i32 and promote f32 to f64. This is necessary
// in order to interface with JavaScript. For non-web/non-JS embeddings,
// setting this to 0 may be desirable.
// Whether to lower i64 parameters and return values for function
// imports/exports. This is done by lowering them to pairs of i32 and should
// only be needed on JS engines that do not have Wasm/BigInt integration.
// This is automatically enabled when WASM_BIGINT is disabled.
// [link]
// [deprecated]
var LEGALIZE_JS_FFI = true;
var LEGALIZE_JS_FFI = false;

// Ports

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7 changes: 2 additions & 5 deletions tools/link.py
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Expand Up @@ -1120,9 +1120,6 @@ def limit_incoming_module_api():
exit_with_error('explicitly setting EXIT_RUNTIME not compatible with STANDALONE_WASM. EXIT_RUNTIME will always be True for programs (with a main function) and False for reactors (not main function).')
settings.EXIT_RUNTIME = settings.EXPECT_MAIN
settings.IGNORE_MISSING_MAIN = 0
# the wasm must be runnable without the JS, so there cannot be anything that
# requires JS legalization
default_setting('LEGALIZE_JS_FFI', 0)
if 'MEMORY_GROWTH_LINEAR_STEP' in user_settings:
exit_with_error('MEMORY_GROWTH_LINEAR_STEP is not compatible with STANDALONE_WASM')
if 'MEMORY_GROWTH_GEOMETRIC_CAP' in user_settings:
Expand Down Expand Up @@ -1642,8 +1639,8 @@ def limit_incoming_module_api():
# module names buys nothing and would break that rewrite.
settings.MINIFY_WASM_IMPORTED_MODULES = not settings.WASM_ESM_INTEGRATION

if settings.WASM_BIGINT:
settings.LEGALIZE_JS_FFI = 0
if not settings.WASM_BIGINT:
default_setting('LEGALIZE_JS_FFI', 1)

if settings.SINGLE_FILE and settings.GENERATE_SOURCE_MAP:
diagnostics.warning('emcc', 'SINGLE_FILE disables source map support (which requires a .map file)')
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