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fix MIR fn-ptr pretty-printing #82176

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Feb 21, 2021
Merged

fix MIR fn-ptr pretty-printing #82176

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b08bc78
fix MIR fn-ptr pretty-printing
RalfJung Feb 16, 2021
e906745
fn ptr pretty printing: fall back to raw ptr printing
RalfJung Feb 20, 2021
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20 changes: 12 additions & 8 deletions compiler/rustc_middle/src/ty/print/pretty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1030,15 +1030,19 @@ pub trait PrettyPrinter<'tcx>:
)?;
}
(Scalar::Ptr(ptr), ty::FnPtr(_)) => {
// FIXME: this can ICE when the ptr is dangling or points to a non-function.
// We should probably have a helper method to share code with the "Byte strings"
// FIXME: We should probably have a helper method to share code with the "Byte strings"
// printing above (which also has to handle pointers to all sorts of things).
let instance = self.tcx().global_alloc(ptr.alloc_id).unwrap_fn();
self = self.typed_value(
|this| this.print_value_path(instance.def_id(), instance.substs),
|this| this.print_type(ty),
" as ",
)?;
match self.tcx().get_global_alloc(ptr.alloc_id) {
Some(GlobalAlloc::Function(instance)) => {
self = self.typed_value(
|this| this.print_value_path(instance.def_id(), instance.substs),
|this| this.print_type(ty),
" as ",
)?;
}
Some(_) => p!("<non-executable memory>"),
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I think we should just print the pointer as if it were a raw pointer here, otherwise we lose information that may be helpful in debugging the situation.

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You mean like this? (I don't actually know what I am doing here, as said before, this code is rather confusing.^^)

None => p!("<dangling pointer>"),
}
}
// For function type zsts just printing the path is enough
(Scalar::Int(int), ty::FnDef(d, s)) if int == ScalarInt::ZST => {
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2 changes: 1 addition & 1 deletion compiler/rustc_mir/src/interpret/operand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ impl<Tag: Copy> std::fmt::Display for ImmTy<'tcx, Tag> {
}
ScalarMaybeUninit::Uninit => cx.typed_value(
|mut this| {
this.write_str("{uninit ")?;
this.write_str("uninit ")?;
Ok(this)
},
|this| this.print_type(ty),
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