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[DRAFT] make panic overflow messages include values #154231

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e6741f6
make panic overflow messages include values
asquared31415 Mar 22, 2026
1e2aeaa
implement in minicore without fancy printing
asquared31415 Mar 22, 2026
1799da2
impl panics in codegen_cranelift
asquared31415 Mar 23, 2026
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44 changes: 37 additions & 7 deletions compiler/rustc_codegen_cranelift/example/mini_core.rs
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Expand Up @@ -493,18 +493,48 @@ macro_rules! panic_const {
}

panic_const! {
panic_const_add_overflow = "attempt to add with overflow",
panic_const_sub_overflow = "attempt to subtract with overflow",
panic_const_mul_overflow = "attempt to multiply with overflow",
panic_const_div_overflow = "attempt to divide with overflow",
panic_const_rem_overflow = "attempt to calculate the remainder with overflow",
panic_const_neg_overflow = "attempt to negate with overflow",
panic_const_shr_overflow = "attempt to shift right with overflow",
panic_const_shl_overflow = "attempt to shift left with overflow",
panic_const_div_by_zero = "attempt to divide by zero",
panic_const_rem_by_zero = "attempt to calculate the remainder with a divisor of zero",
}

macro_rules! panic_overflow {
($($lang_unsigned:ident, $lang_signed:ident = $message:tt,)+) => {
$(
#[cfg_attr(not(panic = "immediate-abort"), inline(never), cold)]
#[cfg_attr(panic = "immediate-abort", inline)]
#[track_caller]
#[lang = stringify!($lang_unsigned)]
pub fn $lang_unsigned(_lhs: u128, _rhs: u128) -> ! {
unsafe {
libc::printf($message as *const str as *const i8);
intrinsics::abort()
}
}
#[cfg_attr(not(panic = "immediate-abort"), inline(never), cold)]
#[cfg_attr(panic = "immediate-abort", inline)]
#[track_caller]
#[lang = stringify!($lang_signed)]
pub fn $lang_signed(_lhs: i128, _rhs: i128) -> ! {
unsafe {
libc::printf($message as *const str as *const i8);
intrinsics::abort()
}
}
)+
};
}

panic_overflow! {
panic_add_overflow_unsigned, panic_add_overflow_signed = "attempt to add with overflow",
panic_sub_overflow_unsigned, panic_sub_overflow_signed = "attempt to subtract with overflow",
panic_mul_overflow_unsigned, panic_mul_overflow_signed = "attempt to multiply with overflow",
panic_div_overflow_unsigned, panic_div_overflow_signed = "attempt to divide with overflow",
panic_rem_overflow_unsigned, panic_rem_overflow_signed = "attempt to calculate the remainder with overflow",
panic_shl_overflow_unsigned, panic_shl_overflow_signed = "attempt to shift left with overflow",
panic_shr_overflow_unsigned, panic_shr_overflow_signed = "attempt to shift left right with overflow",
}

#[lang = "panic_bounds_check"]
#[track_caller]
fn panic_bounds_check(index: usize, len: usize) -> ! {
Expand Down
44 changes: 44 additions & 0 deletions compiler/rustc_codegen_cranelift/src/base.rs
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Expand Up @@ -434,6 +434,50 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
source_info.span,
)
}
AssertKind::Overflow(binop, lhs, rhs) => {
let tcx = fx.tcx;
let is_signed = lhs.ty(fx.mir, tcx).is_signed();

use rustc_hir::LangItem::*;
let lang = match (binop, is_signed) {
(mir::BinOp::Add, true) => PanicAddOverflowSigned,
(mir::BinOp::Add, false) => PanicAddOverflowUnsigned,
(mir::BinOp::Sub, true) => PanicSubOverflowSigned,
(mir::BinOp::Sub, false) => PanicSubOverflowUnsigned,
(mir::BinOp::Mul, true) => PanicMulOverflowSigned,
(mir::BinOp::Mul, false) => PanicMulOverflowUnsigned,
(mir::BinOp::Div, true) => PanicDivOverflowSigned,
(mir::BinOp::Div, false) => PanicDivOverflowUnsigned,
(mir::BinOp::Rem, true) => PanicRemOverflowSigned,
(mir::BinOp::Rem, false) => PanicRemOverflowUnsigned,
(mir::BinOp::Shl, true) => PanicShlOverflowSigned,
(mir::BinOp::Shl, false) => PanicShlOverflowUnsigned,
(mir::BinOp::Shr, true) => PanicShrOverflowSigned,
(mir::BinOp::Shr, false) => PanicShrOverflowUnsigned,
_ => bug!("binop {:?} should not have overflow assert", binop),
};

let lhs = codegen_operand(fx, lhs).load_scalar(fx);
let rhs = codegen_operand(fx, rhs).load_scalar(fx);

let i128_ty = tcx.types.i128;
let clif_128_ty = fx.clif_type(i128_ty).unwrap();

let lhs =
clif_int_or_float_cast(fx, lhs, is_signed, clif_128_ty, is_signed);
let rhs =
clif_int_or_float_cast(fx, rhs, is_signed, clif_128_ty, is_signed);

let location = fx.get_caller_location(source_info).load_scalar(fx);

codegen_panic_inner(
fx,
lang,
&[lhs, rhs, location],
*unwind,
source_info.span,
)
}
_ => {
let location = fx.get_caller_location(source_info).load_scalar(fx);

Expand Down
44 changes: 37 additions & 7 deletions compiler/rustc_codegen_gcc/example/mini_core.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -505,18 +505,48 @@ macro_rules! panic_const {
}

panic_const! {
panic_const_add_overflow = "attempt to add with overflow",
panic_const_sub_overflow = "attempt to subtract with overflow",
panic_const_mul_overflow = "attempt to multiply with overflow",
panic_const_div_overflow = "attempt to divide with overflow",
panic_const_rem_overflow = "attempt to calculate the remainder with overflow",
panic_const_neg_overflow = "attempt to negate with overflow",
panic_const_shr_overflow = "attempt to shift right with overflow",
panic_const_shl_overflow = "attempt to shift left with overflow",
panic_const_div_by_zero = "attempt to divide by zero",
panic_const_rem_by_zero = "attempt to calculate the remainder with a divisor of zero",
}

macro_rules! panic_overflow {
($($lang_unsigned:ident, $lang_signed:ident = $message:tt,)+) => {
$(
#[cfg_attr(not(panic = "immediate-abort"), inline(never), cold)]
#[cfg_attr(panic = "immediate-abort", inline)]
#[track_caller]
#[lang = stringify!($lang_unsigned)]
pub fn $lang_unsigned(_lhs: u128, _rhs: u128) -> ! {
unsafe {
libc::printf($message as *const str as *const i8);
intrinsics::abort()
}
}
#[cfg_attr(not(panic = "immediate-abort"), inline(never), cold)]
#[cfg_attr(panic = "immediate-abort", inline)]
#[track_caller]
#[lang = stringify!($lang_signed)]
pub fn $lang_signed(_lhs: i128, _rhs: i128) -> ! {
unsafe {
libc::printf($message as *const str as *const i8);
intrinsics::abort()
}
}
)+
};
}

panic_overflow! {
panic_add_overflow_unsigned, panic_add_overflow_signed = "attempt to add with overflow",
panic_sub_overflow_unsigned, panic_sub_overflow_signed = "attempt to subtract with overflow",
panic_mul_overflow_unsigned, panic_mul_overflow_signed = "attempt to multiply with overflow",
panic_div_overflow_unsigned, panic_div_overflow_signed = "attempt to divide with overflow",
panic_rem_overflow_unsigned, panic_rem_overflow_signed = "attempt to calculate the remainder with overflow",
panic_shl_overflow_unsigned, panic_shl_overflow_signed = "attempt to shift left with overflow",
panic_shr_overflow_unsigned, panic_shr_overflow_signed = "attempt to shift left right with overflow",
}

#[lang = "panic_cannot_unwind"]
fn panic_cannot_unwind() -> ! {
unsafe {
Expand Down
74 changes: 62 additions & 12 deletions compiler/rustc_codegen_ssa/src/mir/block.rs
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Expand Up @@ -740,40 +740,90 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
let location = self.get_caller_location(bx, terminator.source_info).immediate();

// Put together the arguments to the panic entry point.
let (lang_item, args) = match msg {
let ((fn_abi, llfn, instance), args) = match msg {
AssertKind::BoundsCheck { len, index } => {
let len = self.codegen_operand(bx, len).immediate();
let index = self.codegen_operand(bx, index).immediate();
// It's `fn panic_bounds_check(index: usize, len: usize)`,
// and `#[track_caller]` adds an implicit third argument.
(LangItem::PanicBoundsCheck, vec![index, len, location])
(
common::build_langcall(bx, span, LangItem::PanicBoundsCheck),
vec![index, len, location],
)
}
AssertKind::MisalignedPointerDereference { required, found } => {
let required = self.codegen_operand(bx, required).immediate();
let found = self.codegen_operand(bx, found).immediate();
// It's `fn panic_misaligned_pointer_dereference(required: usize, found: usize)`,
// and `#[track_caller]` adds an implicit third argument.
(LangItem::PanicMisalignedPointerDereference, vec![required, found, location])
}
AssertKind::NullPointerDereference => {
// It's `fn panic_null_pointer_dereference()`,
// `#[track_caller]` adds an implicit argument.
(LangItem::PanicNullPointerDereference, vec![location])
(
common::build_langcall(bx, span, LangItem::PanicMisalignedPointerDereference),
vec![required, found, location],
)
}
AssertKind::InvalidEnumConstruction(source) => {
let source = self.codegen_operand(bx, source).immediate();
// It's `fn panic_invalid_enum_construction(source: u128)`,
// `#[track_caller]` adds an implicit argument.
(LangItem::PanicInvalidEnumConstruction, vec![source, location])
(
common::build_langcall(bx, span, LangItem::PanicInvalidEnumConstruction),
vec![source, location],
)
}
AssertKind::Overflow(binop, lhs, rhs) => {
let tcx = bx.tcx();

let is_signed = lhs.ty(self.mir, tcx).is_signed();

let lang = match (binop, is_signed) {
(mir::BinOp::Add, true) => LangItem::PanicAddOverflowSigned,
(mir::BinOp::Add, false) => LangItem::PanicAddOverflowUnsigned,
(mir::BinOp::Sub, true) => LangItem::PanicSubOverflowSigned,
(mir::BinOp::Sub, false) => LangItem::PanicSubOverflowUnsigned,
(mir::BinOp::Mul, true) => LangItem::PanicMulOverflowSigned,
(mir::BinOp::Mul, false) => LangItem::PanicMulOverflowUnsigned,
(mir::BinOp::Div, true) => LangItem::PanicDivOverflowSigned,
(mir::BinOp::Div, false) => LangItem::PanicDivOverflowUnsigned,
(mir::BinOp::Rem, true) => LangItem::PanicRemOverflowSigned,
(mir::BinOp::Rem, false) => LangItem::PanicRemOverflowUnsigned,
(mir::BinOp::Shl, true) => LangItem::PanicShlOverflowSigned,
(mir::BinOp::Shl, false) => LangItem::PanicShlOverflowUnsigned,
(mir::BinOp::Shr, true) => LangItem::PanicShrOverflowSigned,
(mir::BinOp::Shr, false) => LangItem::PanicShrOverflowUnsigned,
_ => bug!("binop {:?} should not have overflow assert", binop),
};

let (lhs, rhs) = if is_signed {
let i128_ty = tcx.types.i128;
let i128_llty = bx.immediate_backend_type(bx.layout_of(i128_ty));

let lhs = self.codegen_operand(bx, lhs).immediate();
let lhs = bx.sext(lhs, i128_llty);
let rhs = self.codegen_operand(bx, rhs).immediate();
let rhs = bx.sext(rhs, i128_llty);

(lhs, rhs)
} else {
let u128_ty = tcx.types.u128;
let u128_llty = bx.immediate_backend_type(bx.layout_of(u128_ty));

let lhs = self.codegen_operand(bx, lhs).immediate();
let lhs = bx.zext(lhs, u128_llty);
let rhs = self.codegen_operand(bx, rhs).immediate();
let rhs = bx.zext(rhs, u128_llty);

(lhs, rhs)
};

// signature fn(lhs, rhs), plus #[track_caller] location
(common::build_langcall(bx, span, lang), vec![lhs, rhs, location])
}
_ => {
// It's `pub fn panic_...()` and `#[track_caller]` adds an implicit argument.
(msg.panic_function(), vec![location])
(common::build_langcall(bx, span, msg.panic_function()), vec![location])
}
};

let (fn_abi, llfn, instance) = common::build_langcall(bx, span, lang_item);

// Codegen the actual panic invoke/call.
let merging_succ = helper.do_call(
self,
Expand Down
27 changes: 17 additions & 10 deletions compiler/rustc_hir/src/lang_items.rs
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Expand Up @@ -289,16 +289,23 @@ language_item_table! {
PanicCannotUnwind, sym::panic_cannot_unwind, panic_cannot_unwind, Target::Fn, GenericRequirement::Exact(0);
PanicInCleanup, sym::panic_in_cleanup, panic_in_cleanup, Target::Fn, GenericRequirement::Exact(0);
/// Constant panic messages, used for codegen of MIR asserts.
PanicAddOverflow, sym::panic_const_add_overflow, panic_const_add_overflow, Target::Fn, GenericRequirement::None;
PanicSubOverflow, sym::panic_const_sub_overflow, panic_const_sub_overflow, Target::Fn, GenericRequirement::None;
PanicMulOverflow, sym::panic_const_mul_overflow, panic_const_mul_overflow, Target::Fn, GenericRequirement::None;
PanicDivOverflow, sym::panic_const_div_overflow, panic_const_div_overflow, Target::Fn, GenericRequirement::None;
PanicRemOverflow, sym::panic_const_rem_overflow, panic_const_rem_overflow, Target::Fn, GenericRequirement::None;
PanicNegOverflow, sym::panic_const_neg_overflow, panic_const_neg_overflow, Target::Fn, GenericRequirement::None;
PanicShrOverflow, sym::panic_const_shr_overflow, panic_const_shr_overflow, Target::Fn, GenericRequirement::None;
PanicShlOverflow, sym::panic_const_shl_overflow, panic_const_shl_overflow, Target::Fn, GenericRequirement::None;
PanicDivZero, sym::panic_const_div_by_zero, panic_const_div_by_zero, Target::Fn, GenericRequirement::None;
PanicRemZero, sym::panic_const_rem_by_zero, panic_const_rem_by_zero, Target::Fn, GenericRequirement::None;
PanicAddOverflowSigned, sym::panic_add_overflow_signed, panic_add_overflow_signed, Target::Fn, GenericRequirement::None;
PanicAddOverflowUnsigned, sym::panic_add_overflow_unsigned, panic_add_overflow_unsigned, Target::Fn, GenericRequirement::None;
PanicSubOverflowSigned, sym::panic_sub_overflow_signed, panic_sub_overflow_signed, Target::Fn, GenericRequirement::None;
PanicSubOverflowUnsigned, sym::panic_sub_overflow_unsigned, panic_sub_overflow_unsigned, Target::Fn, GenericRequirement::None;
PanicMulOverflowSigned, sym::panic_mul_overflow_signed, panic_mul_overflow_signed, Target::Fn, GenericRequirement::None;
PanicMulOverflowUnsigned, sym::panic_mul_overflow_unsigned, panic_mul_overflow_unsigned, Target::Fn, GenericRequirement::None;
PanicDivOverflowSigned, sym::panic_div_overflow_signed, panic_div_overflow_signed, Target::Fn, GenericRequirement::None;
PanicDivOverflowUnsigned, sym::panic_div_overflow_unsigned, panic_div_overflow_unsigned, Target::Fn, GenericRequirement::None;
PanicRemOverflowSigned, sym::panic_rem_overflow_signed, panic_rem_overflow_signed, Target::Fn, GenericRequirement::None;
PanicRemOverflowUnsigned, sym::panic_rem_overflow_unsigned, panic_rem_overflow_unsigned, Target::Fn, GenericRequirement::None;
PanicShlOverflowSigned, sym::panic_shl_overflow_signed, panic_shl_overflow_signed, Target::Fn, GenericRequirement::None;
PanicShlOverflowUnsigned, sym::panic_shl_overflow_unsigned, panic_shl_overflow_unsigned, Target::Fn, GenericRequirement::None;
PanicShrOverflowSigned, sym::panic_shr_overflow_signed, panic_shr_overflow_signed, Target::Fn, GenericRequirement::None;
PanicShrOverflowUnsigned, sym::panic_shr_overflow_unsigned, panic_shr_overflow_unsigned, Target::Fn, GenericRequirement::None;
PanicNegOverflow, sym::panic_const_neg_overflow, panic_const_neg_overflow, Target::Fn, GenericRequirement::None;
PanicDivZero, sym::panic_const_div_by_zero, panic_const_div_by_zero, Target::Fn, GenericRequirement::None;
PanicRemZero, sym::panic_const_rem_by_zero, panic_const_rem_by_zero, Target::Fn, GenericRequirement::None;
PanicCoroutineResumed, sym::panic_const_coroutine_resumed, panic_const_coroutine_resumed, Target::Fn, GenericRequirement::None;
PanicAsyncFnResumed, sym::panic_const_async_fn_resumed, panic_const_async_fn_resumed, Target::Fn, GenericRequirement::None;
PanicAsyncGenFnResumed, sym::panic_const_async_gen_fn_resumed, panic_const_async_gen_fn_resumed, Target::Fn, GenericRequirement::None;
Expand Down
20 changes: 12 additions & 8 deletions compiler/rustc_middle/src/mir/terminator.rs
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Expand Up @@ -176,15 +176,19 @@
pub fn panic_function(&self) -> LangItem {
use AssertKind::*;
match self {
Overflow(BinOp::Add, _, _) => LangItem::PanicAddOverflow,
Overflow(BinOp::Sub, _, _) => LangItem::PanicSubOverflow,
Overflow(BinOp::Mul, _, _) => LangItem::PanicMulOverflow,
Overflow(BinOp::Div, _, _) => LangItem::PanicDivOverflow,
Overflow(BinOp::Rem, _, _) => LangItem::PanicRemOverflow,
OverflowNeg(_) => LangItem::PanicNegOverflow,
Overflow(BinOp::Shr, _, _) => LangItem::PanicShrOverflow,
Overflow(BinOp::Shl, _, _) => LangItem::PanicShlOverflow,
Overflow(
BinOp::Add
| BinOp::Sub
| BinOp::Mul
| BinOp::Div
| BinOp::Rem
| BinOp::Shr
| BinOp::Shl,
_,
_,
) => bug!("Binops handled elsewhere"),

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Binops handled elsewhere
Overflow(op, _, _) => bug!("{:?} cannot overflow", op),
OverflowNeg(_) => LangItem::PanicNegOverflow,
DivisionByZero(_) => LangItem::PanicDivZero,
RemainderByZero(_) => LangItem::PanicRemZero,
ResumedAfterReturn(CoroutineKind::Coroutine(_)) => LangItem::PanicCoroutineResumed,
Expand Down
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