Include the name of the created tag in TB's Reborrow events #4387
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saethlin
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| @@ -15,7 +15,7 @@ use crate::*; | |||
| #[derive(Clone, Copy, Debug)] | |||
| pub enum AccessCause { | |||
| Explicit(AccessKind), | |||
| Reborrow, | |||
| Reborrow(BorTag), | |||
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| Reborrow(BorTag), | |
| /// The tag here is the one *newly created* by the reborrow that caused the access. | |
| Reborrow(BorTag), |
| @@ -1,11 +1,11 @@ | |||
| error: Undefined Behavior: reborrow through <TAG> at ALLOC[0x0] is forbidden | |||
| error: Undefined Behavior: reborrow to create <TAG> through <TAG> at ALLOC[0x0] is forbidden | |||
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The new tag doesn't matter here, does it? Creating it failed, so it can't possibly occur anywhere else in the state already.
| @@ -21,7 +21,7 @@ help: the accessed tag <TAG> later transitioned to Active due to a child write a | |||
| LL | *x = 1; | |||
| | ^^^^^^ | |||
| = help: this transition corresponds to the first write to a 2-phase borrowed mutable reference | |||
| help: the accessed tag <TAG> later transitioned to Frozen due to a reborrow (acting as a foreign read access) at offsets [OFFSET] | |||
| help: the accessed tag <TAG> later transitioned to Frozen due to a reborrow to create <TAG> (acting as a foreign read access) at offsets [OFFSET] | |||
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Is it clear that the newly created tag is always the more interesting one here, rather than the tag of the pointer that is the input to the reborrow?
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Yes, because it can be traced with -Zmiri-track-pointer-tag (which tells you the parent tag), but you can't find the child tag from the parent.
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Yeah, that's why the alternative solution to the linked issue is to make tag tracking also log reborrows of the tracked tag. But I suspect that will be an unusable amount of information written to the terminal.
This fixes #4386 by recording and mentioning the created tag in a Reborrow event.