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Ensure f32 deserialized from f64 and vice versa preserve NaN sign

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This commit is contained in:
David Tolnay 2023-10-25 19:37:47 -07:00
parent a091a07aa2
commit d2fcc346b9
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GPG Key ID: F9BA143B95FF6D82
2 changed files with 30 additions and 2 deletions
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6
serde/build.rs
View File

@ -27,6 +27,12 @@ fn main() {
println!("cargo:rustc-cfg=no_relaxed_trait_bounds");
}
// f32::copysign and f64::copysign stabilized in Rust 1.35.
// https://blog.rust-lang.org/2019/05/23/Rust-1.35.0.html#copy-the-sign-of-a-floating-point-number-onto-another
if minor < 35 {
println!("cargo:rustc-cfg=no_float_copysign");
}
// Current minimum supported version of serde_derive crate is Rust 1.56.
if minor < 56 {
println!("cargo:rustc-cfg=no_serde_derive");

26
serde/src/de/impls.rs
View File

@ -180,6 +180,28 @@ macro_rules! num_as_self {
};
}
macro_rules! num_as_copysign_self {
($ty:ident : $visit:ident) => {
#[inline]
fn $visit<E>(self, v: $ty) -> Result<Self::Value, E>
where
E: Error,
{
#[cfg(no_float_copysign)]
{
Ok(v as Self::Value)
}
#[cfg(not(no_float_copysign))]
{
// Preserve sign of NaN. The `as` produces a nondeterministic sign.
let sign = if v.is_sign_positive() { 1.0 } else { -1.0 };
Ok((v as Self::Value).copysign(sign))
}
}
};
}
macro_rules! int_to_int {
($ty:ident : $visit:ident) => {
#[inline]
@ -351,7 +373,7 @@ impl_deserialize_num! {
impl_deserialize_num! {
f32, deserialize_f32
num_self!(f32:visit_f32);
num_as_self!(f64:visit_f64);
num_as_copysign_self!(f64:visit_f64);
num_as_self!(i8:visit_i8 i16:visit_i16 i32:visit_i32 i64:visit_i64);
num_as_self!(u8:visit_u8 u16:visit_u16 u32:visit_u32 u64:visit_u64);
}
@ -359,7 +381,7 @@ impl_deserialize_num! {
impl_deserialize_num! {
f64, deserialize_f64
num_self!(f64:visit_f64);
num_as_self!(f32:visit_f32);
num_as_copysign_self!(f32:visit_f32);
num_as_self!(i8:visit_i8 i16:visit_i16 i32:visit_i32 i64:visit_i64);
num_as_self!(u8:visit_u8 u16:visit_u16 u32:visit_u32 u64:visit_u64);
}