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| author | Ralf Jung <post@ralfj.de> | 2019-08-30 09:31:21 +0200 |
|---|---|---|
| committer | Ralf Jung <post@ralfj.de> | 2019-08-30 09:35:33 +0200 |
| commit | e7fed140a4db638562077afc0ec5ef174a25bcc0 (patch) | |
| tree | af1f9f5a8b9a4655a1c6a6bc223745d666941f79 | |
| parent | cf574091fb10496a72b8f105d6f8f14f3eff0db6 (diff) | |
| download | rust-e7fed140a4db638562077afc0ec5ef174a25bcc0.tar.gz rust-e7fed140a4db638562077afc0ec5ef174a25bcc0.zip | |
explain why REF_AS_USIZE is important
| -rw-r--r-- | src/test/ui/consts/const-eval/ub-ref.rs | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/src/test/ui/consts/const-eval/ub-ref.rs b/src/test/ui/consts/const-eval/ub-ref.rs index bbab85c2121..03ac12c8b1a 100644 --- a/src/test/ui/consts/const-eval/ub-ref.rs +++ b/src/test/ui/consts/const-eval/ub-ref.rs @@ -11,6 +11,9 @@ const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) }; const NULL: &u16 = unsafe { mem::transmute(0usize) }; //~^ ERROR it is undefined behavior to use this value +// It is very important that we reject this: We do promote `&(4 * REF_AS_USIZE)`, +// but that would fail to compile; so we ended up breaking user code that would +// have worked fine had we not promoted. const REF_AS_USIZE: usize = unsafe { mem::transmute(&0) }; //~^ ERROR it is undefined behavior to use this value |