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fix(runtime): large integers print V8 shortest round-trip, not exact (#6127) #6176

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Merged
proggeramlug merged 2 commits into from
Jul 9, 2026
Merged

fix(runtime): large integers print V8 shortest round-trip, not exact (#6127) #6176

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d640967
fix(runtime): large integers print V8 shortest round-trip, not exact …
Jul 9, 2026
7397b45
fix(runtime): js_console_log_dynamic fallback uses the shared JS numb…
Jul 9, 2026
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20 changes: 12 additions & 8 deletions crates/perry-runtime/src/builtins/console.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,7 @@ pub extern "C" fn js_console_log(value: JSValue) {
// Match Node/V8 console.log semantics: distinguish -0 from 0
if is_negative_zero(n) {
println!("-0");
} else if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
} else if n.fract() == 0.0 && n.abs() < INT_EXACT_FASTPATH_LIMIT {
// Print integers without decimal point
println!("{}", n as i64);
} else {
Expand Down Expand Up @@ -97,10 +97,14 @@ pub extern "C" fn js_console_log_dynamic(value: f64) {
}
} else if is_negative_zero(n) {
println!("{}-0", p);
} else if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
} else if n.fract() == 0.0 && n.abs() < INT_EXACT_FASTPATH_LIMIT {
println!("{}{}", p, n as i64);
} else {
println!("{}{}", p, n);
// Match `js_console_error_dynamic` / `js_console_warn_dynamic`: use the
// shared JS formatter (shortest round-trip + the 1e21/1e-6 exponential
// thresholds), not Rust's `f64` Display — which prints `1e21` as
// `1000000000000000000000` instead of Node's `1e+21` (#6127).
println!("{}{}", p, format_finite_number_js(n));
}
}
}
Expand Down Expand Up @@ -228,7 +232,7 @@ pub extern "C" fn js_console_log_number(value: f64) {
} else {
println!("-Infinity");
}
} else if value.fract() == 0.0 && value.abs() < (i64::MAX as f64) {
} else if value.fract() == 0.0 && value.abs() < INT_EXACT_FASTPATH_LIMIT {
println!("{}", value as i64);
} else {
println!("{}", format_finite_number_js(value));
Expand Down Expand Up @@ -274,7 +278,7 @@ pub extern "C" fn js_console_error_dynamic(value: f64) {
}
} else if is_negative_zero(n) {
eprintln!("-0");
} else if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
} else if n.fract() == 0.0 && n.abs() < INT_EXACT_FASTPATH_LIMIT {
eprintln!("{}", n as i64);
} else {
eprintln!("{}", format_finite_number_js(n));
Expand All @@ -287,7 +291,7 @@ pub extern "C" fn js_console_error_dynamic(value: f64) {
pub extern "C" fn js_console_error_number(value: f64) {
if is_negative_zero(value) {
eprintln!("-0");
} else if value.fract() == 0.0 && value.abs() < (i64::MAX as f64) {
} else if value.fract() == 0.0 && value.abs() < INT_EXACT_FASTPATH_LIMIT {
eprintln!("{}", value as i64);
} else {
eprintln!("{}", format_finite_number_js(value));
Expand Down Expand Up @@ -333,7 +337,7 @@ pub extern "C" fn js_console_warn_dynamic(value: f64) {
}
} else if is_negative_zero(n) {
eprintln!("-0");
} else if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
} else if n.fract() == 0.0 && n.abs() < INT_EXACT_FASTPATH_LIMIT {
eprintln!("{}", n as i64);
} else {
eprintln!("{}", format_finite_number_js(n));
Expand All @@ -346,7 +350,7 @@ pub extern "C" fn js_console_warn_dynamic(value: f64) {
pub extern "C" fn js_console_warn_number(value: f64) {
if is_negative_zero(value) {
eprintln!("-0");
} else if value.fract() == 0.0 && value.abs() < (i64::MAX as f64) {
} else if value.fract() == 0.0 && value.abs() < INT_EXACT_FASTPATH_LIMIT {
eprintln!("{}", value as i64);
} else {
eprintln!("{}", format_finite_number_js(value));
Expand Down
26 changes: 24 additions & 2 deletions crates/perry-runtime/src/builtins/formatting.rs
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Expand Up @@ -119,6 +119,28 @@ pub(crate) fn format_finite_number_js(value: f64) -> String {
}
}

/// 2^53 — the largest magnitude below which every integer is exactly
/// representable as an `f64`. `console.log` / inspect / `util.format('%d')` fast
/// paths print a whole number via a direct `as i64` cast for speed, but that is
/// only the shortest-round-trip decimal *below* this bound. At/above it several
/// integers map to one double, and the exact integer carries more significant
/// digits than V8's shortest decimal (`2**58` → `288230376151711740`, not
/// `…744`); such values must go through `format_finite_number_js`, whose Rust
/// `{}` is shortest-round-trip. Refs #6127.
pub(crate) const INT_EXACT_FASTPATH_LIMIT: f64 = 9_007_199_254_740_992.0;

/// Format a finite, integer-valued `f64` as V8 would: the fast `as i64` cast
/// below 2^53, else the shortest-round-trip formatter. Callers that have already
/// established `value.fract() == 0.0` (or truncated) use this to avoid the exact
/// vs. shortest divergence at large magnitudes. Refs #6127.
pub(crate) fn format_integral_f64(value: f64) -> String {
if value.abs() < INT_EXACT_FASTPATH_LIMIT {
(value as i64).to_string()
} else {
format_finite_number_js(value)
}
}

fn format_util_number(value: f64) -> String {
if value.is_nan() {
"NaN".to_string()
Expand Down Expand Up @@ -1055,7 +1077,7 @@ pub(crate) fn format_jsvalue(value: f64, depth: usize) -> String {
}
} else if is_negative_zero(n) {
"-0".to_string()
} else if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
} else if n.fract() == 0.0 && n.abs() < INT_EXACT_FASTPATH_LIMIT {
(n as i64).to_string()
} else {
format_finite_number_js(n)
Expand Down Expand Up @@ -1716,7 +1738,7 @@ fn format_jsvalue_for_json(value: f64, depth: usize) -> String {
}
} else if is_negative_zero(n) {
"-0".to_string()
} else if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
} else if n.fract() == 0.0 && n.abs() < INT_EXACT_FASTPATH_LIMIT {
(n as i64).to_string()
} else {
format_finite_number_js(n)
Expand Down
7 changes: 5 additions & 2 deletions crates/perry-runtime/src/builtins/formatting/util_format.rs
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Expand Up @@ -272,8 +272,11 @@ pub extern "C" fn js_util_format(arr_ptr: *const crate::array::ArrayHeader) -> f
if t == 0.0 && f.is_sign_negative() {
out.push_str("-0");
} else {
// Integer-truncated, matching Node.
out.push_str(&(t as i64).to_string());
// Integer-truncated, matching Node. Format the
// whole value shortest-round-trip so large
// magnitudes (`%d` of `2**58`) print V8's
// `…740`, not the exact `…744` (#6127).
out.push_str(&super::format_integral_f64(t));
}
}
}
Expand Down
2 changes: 1 addition & 1 deletion crates/perry-runtime/src/builtins/mod.rs
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Expand Up @@ -88,7 +88,7 @@ pub(crate) use formatting::{
boxed_primitive_json_value, boxed_primitive_payload, boxed_primitive_to_string_tag,
format_finite_number_js, format_jsvalue, is_negative_zero, jsvalue_string_content,
InspectCompactGuard, InspectCustomInspectGuard, InspectDepthLimitGuard, InspectGettersGuard,
InspectShowHiddenGuard, InspectSortedGuard,
InspectShowHiddenGuard, InspectSortedGuard, INT_EXACT_FASTPATH_LIMIT,
};

pub use globals::{
Expand Down
2 changes: 1 addition & 1 deletion crates/perry-runtime/src/builtins/table.rs
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Expand Up @@ -54,7 +54,7 @@ fn format_table_cell(value: f64) -> String {
}
} else if is_negative_zero(n) {
"-0".to_string()
} else if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
} else if n.fract() == 0.0 && n.abs() < crate::builtins::INT_EXACT_FASTPATH_LIMIT {
(n as i64).to_string()
} else {
format_finite_number_js(n)
Expand Down
9 changes: 6 additions & 3 deletions crates/perry-runtime/src/date.rs
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Expand Up @@ -1449,10 +1449,13 @@ pub extern "C" fn js_number_to_locale_string(n: f64) -> *mut crate::StringHeader
// `Number.prototype.toLocaleString()` shows up to 3 fraction digits
// (Intl.NumberFormat default `maximumFractionDigits`), trailing
// zeros stripped.
let int_part = abs.trunc() as u64;
let frac = abs - abs.trunc();
// Format integer part with comma every 3 digits (en-US).
let int_str = int_part.to_string();
// Format integer part with comma every 3 digits (en-US). #6127: derive the
// digits from the f64's shortest round-trip (Rust `{}` is always positional,
// never scientific) rather than an exact `as u64` cast — the cast both
// overflows past ~1.8e19 and, in [2^53, 2^64), prints more digits than the
// shortest decimal V8 groups (`2**60` → `…847,000`, not `…846,976`).
let int_str = format!("{}", abs.trunc());
let mut grouped = String::new();
let bytes = int_str.as_bytes();
let len = bytes.len();
Expand Down
6 changes: 4 additions & 2 deletions crates/perry-runtime/src/json/stringify.rs
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Expand Up @@ -97,9 +97,11 @@ pub(crate) unsafe fn write_number(buf: &mut String, value: f64) {
if value.is_nan() || value.is_infinite() {
// JSON has no NaN/Infinity literal; the spec serializes them as null.
buf.push_str("null");
} else if value.fract() == 0.0 && value.abs() < (i64::MAX as f64) {
} else if value.fract() == 0.0 && value.abs() < crate::builtins::INT_EXACT_FASTPATH_LIMIT {
// Fast path for in-range integers (the overwhelming majority of JSON
// numbers); identical to ECMAScript NumberToString over this range.
// numbers); identical to ECMAScript NumberToString below 2^53. Above it
// the exact integer can carry more digits than the shortest round-trip
// (`2**58`), so those fall through to `js_format_f64` in the else (#6127).
let mut itoa_buf = itoa::Buffer::new();
buf.push_str(itoa_buf.format(value as i64));
} else {
Expand Down
4 changes: 3 additions & 1 deletion crates/perry-runtime/src/json/stringify_api.rs
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Expand Up @@ -209,11 +209,13 @@ pub unsafe extern "C" fn js_json_stringify_number(value: f64) -> *mut StringHead
if value.is_nan() || value.is_infinite() {
return js_string_from_bytes(b"null".as_ptr(), 4);
}
if value.fract() == 0.0 && value.abs() < (i64::MAX as f64) {
if value.fract() == 0.0 && value.abs() < crate::builtins::INT_EXACT_FASTPATH_LIMIT {
let mut itoa_buf = itoa::Buffer::new();
let s = itoa_buf.format(value as i64);
return js_string_from_bytes(s.as_ptr(), s.len() as u32);
}
// #6127: at/above 2^53 the exact integer can carry more digits than the
// shortest round-trip (`2**58`), so defer to the shortest-round-trip formatter.
let s = crate::string::js_format_f64(value);
js_string_from_bytes(s.as_ptr(), s.len() as u32)
}
Expand Down
8 changes: 7 additions & 1 deletion crates/perry-runtime/src/node_stream_json.rs
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Expand Up @@ -9,9 +9,15 @@ use crate::object::ObjectHeader;
pub(super) fn push_json_number(buf: &mut String, value: f64) {
if value.is_nan() || value.is_infinite() {
buf.push_str("null");
} else if value.fract() == 0.0 && value.abs() < (i64::MAX as f64) {
} else if value.fract() == 0.0 && value.abs() < crate::builtins::INT_EXACT_FASTPATH_LIMIT {
let mut itoa_buf = itoa::Buffer::new();
buf.push_str(itoa_buf.format(value as i64));
} else if value.fract() == 0.0 {
// #6127: a large integer (`>= 2^53`) must print its shortest round-trip
// decimal in POSITIONAL notation per ECMAScript Number::toString, not the
// exact integer and not `ryu`'s scientific form (`2.88…e17`). The shared
// JS formatter handles the exponent thresholds (`1e21` → `1e+21`).
buf.push_str(&crate::string::js_format_f64(value));
} else {
let mut ryu_buf = ryu::Buffer::new();
buf.push_str(ryu_buf.format(value));
Expand Down
6 changes: 4 additions & 2 deletions crates/perry-runtime/src/object/native_call_method/common_methods.rs
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Expand Up @@ -696,7 +696,9 @@ pub(super) unsafe fn dispatch_common(
} else {
payload
};
let s = if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
let s = if n.fract() == 0.0
&& n.abs() < crate::builtins::INT_EXACT_FASTPATH_LIMIT
{
(n as i64).to_string()
} else {
n.to_string()
Expand Down Expand Up @@ -753,7 +755,7 @@ pub(super) unsafe fn dispatch_common(
crate::value::js_jsvalue_to_string_radix(object, radix_arg.unwrap());
return Some(f64::from_bits(JSValue::string_ptr(str_ptr).bits()));
}
let s = if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
let s = if n.fract() == 0.0 && n.abs() < crate::builtins::INT_EXACT_FASTPATH_LIMIT {
(n as i64).to_string()
} else {
n.to_string()
Expand Down
4 changes: 3 additions & 1 deletion crates/perry-runtime/src/object/native_call_method/primitive_methods.rs
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Expand Up @@ -212,7 +212,9 @@ pub(super) unsafe fn dispatch_primitive(
} else {
payload
};
let s = if n.fract() == 0.0 && n.abs() < (i64::MAX as f64) {
let s = if n.fract() == 0.0
&& n.abs() < crate::builtins::INT_EXACT_FASTPATH_LIMIT
{
(n as i64).to_string()
} else {
n.to_string()
Expand Down
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