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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 f2d73af6d7
1 changed files with 6 additions and 6 deletions
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12
src/consts.rs
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@ -127,7 +127,7 @@ impl<'gcc, 'tcx> StaticMethods for CodegenCx<'gcc, 'tcx> {
// //
// We could remove this hack whenever we decide to drop macOS 10.10 support. // We could remove this hack whenever we decide to drop macOS 10.10 support.
if self.tcx.sess.target.options.is_like_osx { if self.tcx.sess.target.options.is_like_osx {
// The `inspect` method is okay here because we checked relocations, and // The `inspect` method is okay here because we checked for provenance, and
// because we are doing this access to inspect the final interpreter state // because we are doing this access to inspect the final interpreter state
// (not as part of the interpreter execution). // (not as part of the interpreter execution).
// //
@ -296,17 +296,17 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAllocation<'tcx>) -> RValue<'gcc> { pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAllocation<'tcx>) -> RValue<'gcc> {
let alloc = alloc.inner(); let alloc = alloc.inner();
let mut llvals = Vec::with_capacity(alloc.relocations().len() + 1); let mut llvals = Vec::with_capacity(alloc.provenance().len() + 1);
let dl = cx.data_layout(); let dl = cx.data_layout();
let pointer_size = dl.pointer_size.bytes() as usize; let pointer_size = dl.pointer_size.bytes() as usize;
let mut next_offset = 0; let mut next_offset = 0;
for &(offset, alloc_id) in alloc.relocations().iter() { for &(offset, alloc_id) in alloc.provenance().iter() {
let offset = offset.bytes(); let offset = offset.bytes();
assert_eq!(offset as usize as u64, offset); assert_eq!(offset as usize as u64, offset);
let offset = offset as usize; let offset = offset as usize;
if offset > next_offset { if offset > next_offset {
// This `inspect` is okay since we have checked that it is not within a relocation, it // This `inspect` is okay since we have checked that it is not within a pointer with provenance, it
// is within the bounds of the allocation, and it doesn't affect interpreter execution // is within the bounds of the allocation, and it doesn't affect interpreter execution
// (we inspect the result after interpreter execution). Any undef byte is replaced with // (we inspect the result after interpreter execution). Any undef byte is replaced with
// some arbitrary byte value. // some arbitrary byte value.
@ -319,7 +319,7 @@ pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAl
read_target_uint( dl.endian, read_target_uint( dl.endian,
// This `inspect` is okay since it is within the bounds of the allocation, it doesn't // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
// affect interpreter execution (we inspect the result after interpreter execution), // affect interpreter execution (we inspect the result after interpreter execution),
// and we properly interpret the relocation as a relocation pointer offset. // and we properly interpret the provenance as a relocation pointer offset.
alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)), alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)),
) )
.expect("const_alloc_to_llvm: could not read relocation pointer") .expect("const_alloc_to_llvm: could not read relocation pointer")
@ -336,7 +336,7 @@ pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAl
} }
if alloc.len() >= next_offset { if alloc.len() >= next_offset {
let range = next_offset..alloc.len(); let range = next_offset..alloc.len();
// This `inspect` is okay since we have check that it is after all relocations, it is // This `inspect` is okay since we have check that it is after all provenance, it is
// within the bounds of the allocation, and it doesn't affect interpreter execution (we // within the bounds of the allocation, and it doesn't affect interpreter execution (we
// inspect the result after interpreter execution). Any undef byte is replaced with some // inspect the result after interpreter execution). Any undef byte is replaced with some
// arbitrary byte value. // arbitrary byte value.