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Auto merge of #86048 - nbdd0121:no_floating_point, r=Amanieu
core: add unstable no_fp_fmt_parse to disable float formatting code In some projects (e.g. kernel), floating point is forbidden. They can disable hardware floating point support and use `+soft-float` to avoid fp instructions from being generated, but as libcore contains the formatting code for `f32` and `f64`, some fp intrinsics are depended. One could define stubs for these intrinsics that just panic [1], but it means that if any formatting functions are accidentally used, mistake can only be caught during the runtime rather than during compile-time or link-time, and they consume a lot of space without LTO. This patch provides an unstable cfg `no_fp_fmt_parse` to disable these. A panicking stub is still provided for the `Debug` implementation (unfortunately) because there are some SIMD types that use `#[derive(Debug)]`. [1]: https://lkml.org/lkml/2021/4/14/1028
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,15 @@ | ||
| use crate::fmt::{Debug, Formatter, Result}; | ||
|
|
||
| macro_rules! floating { | ||
| ($ty:ident) => { | ||
| #[stable(feature = "rust1", since = "1.0.0")] | ||
| impl Debug for $ty { | ||
| fn fmt(&self, _fmt: &mut Formatter<'_>) -> Result { | ||
| panic!("floating point support is turned off"); | ||
| } | ||
| } | ||
| }; | ||
| } | ||
|
|
||
| floating! { f32 } | ||
| floating! { f64 } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,108 @@ | ||
| //! Shared utilties used by both float and integer formatting. | ||
| #![doc(hidden)] | ||
| #![unstable( | ||
| feature = "numfmt", | ||
| reason = "internal routines only exposed for testing", | ||
| issue = "none" | ||
| )] | ||
|
|
||
| /// Formatted parts. | ||
| #[derive(Copy, Clone, PartialEq, Eq, Debug)] | ||
| pub enum Part<'a> { | ||
| /// Given number of zero digits. | ||
| Zero(usize), | ||
| /// A literal number up to 5 digits. | ||
| Num(u16), | ||
| /// A verbatim copy of given bytes. | ||
| Copy(&'a [u8]), | ||
| } | ||
|
|
||
| impl<'a> Part<'a> { | ||
| /// Returns the exact byte length of given part. | ||
| pub fn len(&self) -> usize { | ||
| match *self { | ||
| Part::Zero(nzeroes) => nzeroes, | ||
| Part::Num(v) => { | ||
| if v < 1_000 { | ||
| if v < 10 { | ||
| 1 | ||
| } else if v < 100 { | ||
| 2 | ||
| } else { | ||
| 3 | ||
| } | ||
| } else { | ||
| if v < 10_000 { 4 } else { 5 } | ||
| } | ||
| } | ||
| Part::Copy(buf) => buf.len(), | ||
| } | ||
| } | ||
|
|
||
| /// Writes a part into the supplied buffer. | ||
| /// Returns the number of written bytes, or `None` if the buffer is not enough. | ||
| /// (It may still leave partially written bytes in the buffer; do not rely on that.) | ||
| pub fn write(&self, out: &mut [u8]) -> Option<usize> { | ||
| let len = self.len(); | ||
| if out.len() >= len { | ||
| match *self { | ||
| Part::Zero(nzeroes) => { | ||
| for c in &mut out[..nzeroes] { | ||
| *c = b'0'; | ||
| } | ||
| } | ||
| Part::Num(mut v) => { | ||
| for c in out[..len].iter_mut().rev() { | ||
| *c = b'0' + (v % 10) as u8; | ||
| v /= 10; | ||
| } | ||
| } | ||
| Part::Copy(buf) => { | ||
| out[..buf.len()].copy_from_slice(buf); | ||
| } | ||
| } | ||
| Some(len) | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Formatted result containing one or more parts. | ||
| /// This can be written to the byte buffer or converted to the allocated string. | ||
| #[allow(missing_debug_implementations)] | ||
| #[derive(Clone)] | ||
| pub struct Formatted<'a> { | ||
| /// A byte slice representing a sign, either `""`, `"-"` or `"+"`. | ||
| pub sign: &'static str, | ||
| /// Formatted parts to be rendered after a sign and optional zero padding. | ||
| pub parts: &'a [Part<'a>], | ||
| } | ||
|
|
||
| impl<'a> Formatted<'a> { | ||
| /// Returns the exact byte length of combined formatted result. | ||
| pub fn len(&self) -> usize { | ||
| let mut len = self.sign.len(); | ||
| for part in self.parts { | ||
| len += part.len(); | ||
| } | ||
| len | ||
| } | ||
|
|
||
| /// Writes all formatted parts into the supplied buffer. | ||
| /// Returns the number of written bytes, or `None` if the buffer is not enough. | ||
| /// (It may still leave partially written bytes in the buffer; do not rely on that.) | ||
| pub fn write(&self, out: &mut [u8]) -> Option<usize> { | ||
| if out.len() < self.sign.len() { | ||
| return None; | ||
| } | ||
| out[..self.sign.len()].copy_from_slice(self.sign.as_bytes()); | ||
|
|
||
| let mut written = self.sign.len(); | ||
| for part in self.parts { | ||
| let len = part.write(&mut out[written..])?; | ||
| written += len; | ||
| } | ||
| Some(written) | ||
| } | ||
| } |
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