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Rollup merge of #101101 - RalfJung:read-pointer-as-bytes, r=oli-obk

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interpret: make read-pointer-as-bytes a CTFE-only error with extra information

Next step in the reaction to https://github.com/rust-lang/rust/issues/99923. Also teaches Miri to implicitly strip provenance in more situations when transmuting pointers to integers, which fixes https://github.com/rust-lang/miri/issues/2456.

Pointer-to-int transmutation during CTFE now produces a message like this:
```
   = help: this code performed an operation that depends on the underlying bytes representing a pointer
   = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
```

r? ``@oli-obk``
This commit is contained in:
Dylan DPC 2022-08-30 11:26:51 +05:30 • committed by GitHub
commit 81f3841cfb
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46 changed files with 631 additions and 336 deletions
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2
compiler/rustc_const_eval/src/interpret/operand.rs
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@ -415,7 +415,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Turn the wide MPlace into a string (must already be dereferenced!)
pub fn read_str(&self, mplace: &MPlaceTy<'tcx, M::Provenance>) -> InterpResult<'tcx, &str> {
let len = mplace.len(self)?;
let bytes = self.read_bytes_ptr(mplace.ptr, Size::from_bytes(len))?;
let bytes = self.read_bytes_ptr_strip_provenance(mplace.ptr, Size::from_bytes(len))?;
let str = std::str::from_utf8(bytes).map_err(|err| err_ub!(InvalidStr(err)))?;
Ok(str)
}