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Do not inline integer literals which are out of range in format_args! #116633

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Do not inline integer literals which are out of range in format_args! #116633

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20 changes: 20 additions & 0 deletions compiler/rustc_ast/src/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1795,6 +1795,26 @@ pub enum LitIntType {
Unsuffixed,
}

impl LitIntType {
pub const fn max_literal_value(&self) -> u128 {
match self {
LitIntType::Signed(IntTy::I8) => i8::MAX as u128,
LitIntType::Signed(IntTy::I16) => i16::MAX as u128,
LitIntType::Signed(IntTy::I32) => i32::MAX as u128,
LitIntType::Signed(IntTy::I64) => i64::MAX as u128,
LitIntType::Signed(IntTy::I128) => i128::MAX as u128,
LitIntType::Signed(IntTy::Isize) => isize::MAX as u128,
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This uses the host's isize, but should be using use the target's isize. Same for usize below.

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Fair. What should I do to obtain these values for the target?

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@lukas-code lukas-code Oct 11, 2023 •
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You can get size of isize and usize from tcx.data_layout.pointer_size. That will return a Size, which has the signed_int_max and unsigned_int_max methods that seem useful. It looks like the nearest tcx is the one in the LoweringContext, which you get as self from here:

rust/compiler/rustc_ast_lowering/src/format.rs

Line 15 in b0ae218

pub(crate) fn lower_format_args(&mut self, sp: Span, fmt: &FormatArgs) -> hir::ExprKind<'hir> {

LitIntType::Unsigned(UintTy::U8) => u8::MAX as u128,
LitIntType::Unsigned(UintTy::U16) => u16::MAX as u128,
LitIntType::Unsigned(UintTy::U32) => u32::MAX as u128,
LitIntType::Unsigned(UintTy::U64) => u64::MAX as u128,
LitIntType::Unsigned(UintTy::U128) => u128::MAX,
LitIntType::Unsigned(UintTy::Usize) => usize::MAX as u128,
LitIntType::Unsuffixed => u128::MAX,
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Suggested change
LitIntType::Unsuffixed => u128::MAX,
LitIntType::Unsuffixed => i32::MAX,

Unsuffixed and unconstrained integer literals should have type i32, even if they overflow.

See the old behavior before inlining: https://rust.godbolt.org/z/PMG7ac4d4

}
}
}

/// Type of the float literal based on provided suffix.
#[derive(Clone, Copy, Encodable, Decodable, Debug, Hash, Eq, PartialEq)]
#[derive(HashStable_Generic)]
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8 changes: 6 additions & 2 deletions compiler/rustc_ast_lowering/src/format.rs
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Expand Up @@ -128,9 +128,13 @@ fn inline_literals(mut fmt: Cow<'_, FormatArgs>) -> Cow<'_, FormatArgs> {
{
literal = Some(s);
} else if let token::LitKind::Integer = lit.kind
&& let Ok(LitKind::Int(n, _)) = LitKind::from_token_lit(lit)
&& let Ok(LitKind::Int(n, ty)) = LitKind::from_token_lit(lit)
{
literal = Some(Symbol::intern(&n.to_string()));
// Check if n fits in the type of the argument. If it doesn't,
// simply don't inline the literal here, the error will be emitted at a later stage.
if n <= ty.max_literal_value() {
literal = Some(Symbol::intern(&n.to_string()));
}
}
}

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3 changes: 3 additions & 0 deletions tests/ui/fmt/issue-116631.rs
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@@ -0,0 +1,3 @@
fn main() {
format_args!("{}\n", 0xffff_ffff_u8); //~ ERROR literal out of range for `u8`
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Should this have a test for each of the different integer types?

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At the very least it should have a test case that covers #115423 (which I don't interpet is about being out of range, but rather about not respecting the type of the literal).

}
11 changes: 11 additions & 0 deletions tests/ui/fmt/issue-116631.stderr
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@@ -0,0 +1,11 @@
error: literal out of range for `u8`
--> $DIR/issue-116631.rs:2:26
|
LL | format_args!("{}\n", 0xffff_ffff_u8);
| ^^^^^^^^^^^^^^ help: consider using the type `u32` instead: `0xffff_ffff_u32`
|
= note: the literal `0xffff_ffff_u8` (decimal `4294967295`) does not fit into the type `u8` and will become `255u8`
= note: `#[deny(overflowing_literals)]` on by default

error: aborting due to previous error