From a5ff09c8f054e8df12a4fc84d0533b9476791d68 Mon Sep 17 00:00:00 2001
From: "Kamat, Trivikram" <16024985+trivikr@users.noreply.github.com>
Date: Wed, 22 Jul 2026 23:30:33 -0700
Subject: [PATCH] ffi: validate fast i32 argument ranges

Add i32 and int32 to Fast API integer validation so optimized calls
reject invalid values instead of allowing V8 to truncate them.

Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: openai:gpt-5.6-sol
---
 lib/internal/ffi/fast-api.js                 | 2 ++
 src/ffi/fast.cc                              | 4 ++--
 test/ffi/test-ffi-fast-integer-validation.js | 7 +++++++
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lib/internal/ffi/fast-api.js b/lib/internal/ffi/fast-api.js
index 11e8c005dee98c..71aaca962d17c4 100644
--- a/lib/internal/ffi/fast-api.js
+++ b/lib/internal/ffi/fast-api.js
@@ -51,6 +51,8 @@ const fastIntegerTypeInfo = {
   int16: { kind: 'number', min: -32768, max: 32767, label: 'an int16' },
   u16: { kind: 'number', min: 0, max: 65535, label: 'a uint16' },
   uint16: { kind: 'number', min: 0, max: 65535, label: 'a uint16' },
+  i32: { kind: 'number', min: -2147483648, max: 2147483647, label: 'an int32' },
+  int32: { kind: 'number', min: -2147483648, max: 2147483647, label: 'an int32' },
   i64: { kind: 'bigint', min: I64_MIN, max: I64_MAX, label: 'an int64' },
   int64: { kind: 'bigint', min: I64_MIN, max: I64_MAX, label: 'an int64' },
   u64: { kind: 'bigint', min: 0n, max: U64_MAX, label: 'a uint64' },
diff --git a/src/ffi/fast.cc b/src/ffi/fast.cc
index 8c4420761fec1d..ce8f0e57b2d1cd 100644
--- a/src/ffi/fast.cc
+++ b/src/ffi/fast.cc
@@ -164,8 +164,8 @@ bool SignatureNeedsFastIntegerValidation(const FFIFunction& fn) {
   for (const std::string& name : fn.arg_type_names) {
     if (name == "bool" || name == "char" || name == "i8" || name == "int8" ||
         name == "u8" || name == "uint8" || name == "i16" || name == "int16" ||
-        name == "u16" || name == "uint16" || name == "i64" || name == "int64" ||
-        name == "u64" || name == "uint64") {
+        name == "u16" || name == "uint16" || name == "i32" || name == "int32" ||
+        name == "i64" || name == "int64" || name == "u64" || name == "uint64") {
       return true;
     }
   }
diff --git a/test/ffi/test-ffi-fast-integer-validation.js b/test/ffi/test-ffi-fast-integer-validation.js
index 49fd1364948c35..d75cec0cf0eac6 100644
--- a/test/ffi/test-ffi-fast-integer-validation.js
+++ b/test/ffi/test-ffi-fast-integer-validation.js
@@ -28,6 +28,8 @@ test('fast FFI validates integer argument ranges', () => {
 
     function callU16(value) { return functions.add_u16(value, 0); }
 
+    function callI32(value) { return functions.add_i32(value, 0); }
+
     function callI64(value) { return functions.add_i64(value, 0n); }
 
     function callU64(value) { return functions.add_u64(value, 0n); }
@@ -37,6 +39,7 @@ test('fast FFI validates integer argument ranges', () => {
       [callU8, 0],
       [callI16, 0],
       [callU16, 0],
+      [callI32, 0],
       [callI64, 0n],
       [callU64, 0n],
     ]) {
@@ -48,6 +51,10 @@ test('fast FFI validates integer argument ranges', () => {
     assert.throws(() => callU8(256), expect);
     assert.throws(() => callI16(32768), expect);
     assert.throws(() => callU16(65536), expect);
+    assert.throws(() => callI32(2147483648), expect);
+    assert.throws(() => callI32(-2147483649), expect);
+    assert.throws(() => callI32(1.5), expect);
+    assert.throws(() => callI32('1'), expect);
     assert.throws(() => callI64(2n ** 63n), expect);
     assert.throws(() => callU64(2n ** 64n), expect);
   } finally {