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Rollup merge of #114992 - RalfJung:rustc_do_not_const_check, r=b-naber

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const-eval: ensure we never const-execute a function marked rustc_do_not_const_check
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Matthias Krüger 2023-08-20 00:28:33 +02:00 committed by GitHub
commit bb3cf24d15
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1 changed files with 21 additions and 32 deletions
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53
compiler/rustc_const_eval/src/const_eval/machine.rs
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@ -427,52 +427,41 @@ fn load_mir(
fn find_mir_or_eval_fn(
ecx: &mut InterpCx<'mir, 'tcx, Self>,
instance: ty::Instance<'tcx>,
orig_instance: ty::Instance<'tcx>,
_abi: CallAbi,
args: &[FnArg<'tcx>],
dest: &PlaceTy<'tcx>,
ret: Option<mir::BasicBlock>,
_unwind: mir::UnwindAction, // unwinding is not supported in consts
) -> InterpResult<'tcx, Option<(&'mir mir::Body<'tcx>, ty::Instance<'tcx>)>> {
debug!("find_mir_or_eval_fn: {:?}", instance);
debug!("find_mir_or_eval_fn: {:?}", orig_instance);
// Replace some functions.
let Some(instance) = ecx.hook_special_const_fn(orig_instance, args, dest, ret)? else {
// Call has already been handled.
return Ok(None);
};
// Only check non-glue functions
if let ty::InstanceDef::Item(def) = instance.def {
// Execution might have wandered off into other crates, so we cannot do a stability-
// sensitive check here. But we can at least rule out functions that are not const
// at all.
if !ecx.tcx.is_const_fn_raw(def) {
// allow calling functions inside a trait marked with #[const_trait].
if !ecx.tcx.is_const_default_method(def) {
// We certainly do *not* want to actually call the fn
// though, so be sure we return here.
throw_unsup_format!("calling non-const function `{}`", instance)
}
}
let Some(new_instance) = ecx.hook_special_const_fn(instance, args, dest, ret)? else {
return Ok(None);
};
if new_instance != instance {
// We call another const fn instead.
// However, we return the *original* instance to make backtraces work out
// (and we hope this does not confuse the FnAbi checks too much).
return Ok(Self::find_mir_or_eval_fn(
ecx,
new_instance,
_abi,
args,
dest,
ret,
_unwind,
)?
.map(|(body, _instance)| (body, instance)));
// sensitive check here. But we can at least rule out functions that are not const at
// all. That said, we have to allow calling functions inside a trait marked with
// #[const_trait]. These *are* const-checked!
// FIXME: why does `is_const_fn_raw` not classify them as const?
if (!ecx.tcx.is_const_fn_raw(def) && !ecx.tcx.is_const_default_method(def))
|| ecx.tcx.has_attr(def, sym::rustc_do_not_const_check)
{
// We certainly do *not* want to actually call the fn
// though, so be sure we return here.
throw_unsup_format!("calling non-const function `{}`", instance)
}
}
// This is a const fn. Call it.
Ok(Some((ecx.load_mir(instance.def, None)?, instance)))
// In case of replacement, we return the *original* instance to make backtraces work out
// (and we hope this does not confuse the FnAbi checks too much).
Ok(Some((ecx.load_mir(instance.def, None)?, orig_instance)))
}
fn call_intrinsic(