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ffi: bool changes from uint8 to Boolean after Fast API optimization #64526
Description
Version
main
Platform
macOS 26.5.2
Subsystem
ffi
What steps will reproduce the bug?
add.c
#include <stdint.h>
uint8_t add_u8(uint8_t a, uint8_t b) {
return a + b;
}Build the file
$ cc -dynamiclib add.c -o libadd.dylibUse in repro.js
import { dlopen } from 'node:ffi';
const handle = dlopen(`./libadd.dylib`, {
add_u8: {
arguments: ['bool', 'bool'],
return: 'bool',
},
});
const native = handle.functions.add_u8;
function fn(a, b) {
return native(a, b);
}
eval('%PrepareFunctionForOptimization(fn)');
let result = fn(1, 0);
console.log('unoptimized:', result, typeof result);
eval('%OptimizeFunctionOnNextCall(fn)');
result = fn(1, 0);
console.log('optimized:', result, typeof result);
result = fn(true, false);
console.log('booleans:', result, typeof result);Run
$ node --experimental-ffi --allow-natives-syntax --no-warnings repro.jsHow often does it reproduce? Is there a required condition?
Always
What is the expected behavior? Why is that the expected behavior?
unoptimized: 1 number
optimized: 1 number
TypeError: Argument 0 must be a uint8The optimized numeric call should behave exactly like the unoptimized call.
The final fn(true, false) call should throw ERR_INVALID_ARG_VALUE.
What do you see instead?
unoptimized: 1 number
optimized: true boolean
booleans: true booleanAfter JIT optimization, the return type changes from numeric uint8 to Boolean, and Boolean arguments become accepted
Additional information
No response
Activity
ffi: preserve uint8 semantics for bool fast calls
ffi: preserve uint8 semantics for bool fast calls
ffi: preserve uint8 semantics for bool fast calls