Re: [PATCH v7 5/6] rust: str: add radix prefixed integer parsing functions

[Andreas Hindborg <a.hindborg@kernel.org>]

"Janne Grunau" <j@jannau.net> writes:

> On Tue, Feb 18, 2025 at 02:00:47PM +0100, Andreas Hindborg wrote:
>> Add the trait `ParseInt` for parsing string representations of integers
>> where the string representations are optionally prefixed by a radix
>> specifier. Implement the trait for the primitive integer types.
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
>> ---
>>  rust/kernel/str.rs | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 118 insertions(+)
>>
>> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
>> index db272d2198fcc..8b0d814b47f52 100644
>> --- a/rust/kernel/str.rs
>> +++ b/rust/kernel/str.rs
>> @@ -945,3 +945,121 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>
> [...]
>
>> +    pub trait ParseInt: FromStrRadix + TryFrom<i128> {
>> +        /// Parse a string according to the description in [`Self`].
>> +        fn from_str(src: &BStr) -> Result<Self> {
>> +            match src.deref() {
>> +                [b'-', rest @ ..] => {
>> +                    let (radix, digits) = strip_radix(rest.as_ref());
>> +                    // 2's complement values range from -2^(b-1) to 2^(b-1)-1.
>> +                    // So if we want to parse negative numbers as positive and
>> +                    // later multiply by -1, we have to parse into a larger
>> +                    // integer. We choose i128 as sufficiently large.
>> +                    let val = i128::from_str_radix(
>
> The usage of i128 causes here following link errors on arm64 with
> "rustc 1.84.1 (e71f9a9a9 2025-01-27) (Fedora 1.84.1-1.fc41)"
>
> | ld: rust/kernel.o: in function `<i128>::from_str_radix':
> | /usr/lib/rustlib/src/rust/library/core/src/num/mod.rs:1563:(.text+0x3bc): undefined reference to `__muloti4'
> | ld: /usr/lib/rustlib/src/rust/library/core/src/num/mod.rs:1563:(.text+0x440): undefined reference to `__muloti4'
> | ld: rust/kernel.o: in function `<i128>::overflowing_mul':
> | /usr/lib/rustlib/src/rust/library/core/src/num/int_macros.rs:2517:(.text+0x4b4): undefined reference to `__muloti4'
> | ld: /usr/lib/rustlib/src/rust/library/core/src/num/int_macros.rs:2517:(.text+0x534): undefined reference to `__muloti4'
>
> The errors go away after exchanging i128 with i64 (while breaking the
> parsing for large values).

Thanks for reporting! I will have to find a better way to fix this issue
then.


Best regards,
Andreas Hindborg