Summary

Currently, the Rust frontend's lexer handles non-decimal integer literals (hexadecimal, binary, and octal) by converting them into decimal strings using std::strtol. Since std::strtol is limited by the size of a 64-bit long (on 64-bit systems), any literal exceeding this range (such as large u128 values) is silently saturated to LONG_MAX (2^63−1) or ULONG_MAX. This leads to incorrect constant values being passed to the backend.

Reproducer

I tried this code:

#![feature(no_core)]
#![no_core]
pub fn main() {
        let hex_val: u128 = 0x10000000000000000_u128;
        let bin_val: u128 =
            0b10000000000000000000000000000000000000000000000000000000000000000_u128;
        let oct_val: u128 = 0o2000000000000000000000_u128;
}

Does the code make use of any (1.49) nightly feature ?

• Nightly

Godbolt link

Reproduced on local build of gccrs

Actual behavior

For the reproducible code above

[DEBUG-OLD] RADIXSTRINGHEX: 0x10000000000000000
[DEBUG-OLD] DECIMALSTRINGHEX: 9223372036854775807

[DEBUG-OLD] RADIXSTRINGBIN: 010000000000000000000000000000000000000000000000000000000000000000
[DEBUG-OLD] DECIMALSTRINGBIN: 9223372036854775807

[DEBUG-OLD] RADIXSTRINGOCT: 02000000000000000000000
[DEBUG-OLD] DECIMALSTRINGOCT: 9223372036854775807

Expected behavior

For the reproducible code above

[DEBUG-NEW] RADIXSTRINGHEX: 010000000000000000
[DEBUG-NEW] DECIMALSTRINGHEX: 18446744073709551616

[DEBUG-NEW] RADIXSTRINGBIN: 010000000000000000000000000000000000000000000000000000000000000000
[DEBUG-NEW] DECIMALSTRINGBIN: 18446744073709551616

[DEBUG-NEW] RADIXSTRINGOCT: 02000000000000000000000
[DEBUG-NEW] DECIMALSTRINGOCT: 18446744073709551616

GCC Version

commit hash: 6b891ee