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MutexGuard's Debug implementation is unuseful #57702

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m-ou-se opened this issue Jan 17, 2019 · 0 comments
Closed

MutexGuard's Debug implementation is unuseful #57702

m-ou-se opened this issue Jan 17, 2019 · 0 comments
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C-enhancement Category: An issue proposing an enhancement or a PR with one. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.

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@m-ou-se
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m-ou-se commented Jan 17, 2019 •
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MutexGuard's Debug implementation just forwards to the Mutex's Debug implementation, which will simply print <locked>, because the Mutex was locked (by that very same MutexGuard).

Effectively, this means that the current Debug implementation of MutexGuard is equivalent to:

f.write_str("MutexGuard { lock: Mutex { data: <locked> } }")

Instead, it should not try to lock the mutex, but use its own Deref implementation to print the contents of the mutex.
@m-ou-se m-ou-se mentioned this issue Jan 17, 2019
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@Centril Centril added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. C-enhancement Category: An issue proposing an enhancement or a PR with one. labels Jan 17, 2019
Centril added a commit to Centril/rust that referenced this issue Jan 26, 2019
@Centril
Rollup merge of rust-lang#57703 - m-ou-se:mutexguard-debug, r=cramertj
d638b30 
Make MutexGuard's Debug implementation more useful.

Fixes rust-lang#57702.
Centril added a commit to Centril/rust that referenced this issue Jan 26, 2019
@Centril
Rollup merge of rust-lang#57703 - m-ou-se:mutexguard-debug, r=cramertj
64eff91 
Make MutexGuard's Debug implementation more useful.

Fixes rust-lang#57702.
Centril added a commit to Centril/rust that referenced this issue Jan 26, 2019
@Centril
Rollup merge of rust-lang#57703 - m-ou-se:mutexguard-debug, r=cramertj
1e8fde0 
Make MutexGuard's Debug implementation more useful.

Fixes rust-lang#57702.
@m-ou-se m-ou-se mentioned this issue Mar 27, 2021
Merged
JohnTitor added a commit to JohnTitor/rust that referenced this issue Mar 27, 2021
@JohnTitor
Rollup merge of rust-lang#83559 - m-ou-se:rwlock-guard-debug-fix, r=j…
5dc29e1 
…ackh726

Fix Debug implementation for RwLock{Read,Write}Guard.

This would attempt to print the Debug representation of the lock that the guard has locked, which will try to lock again, fail, and just print `"<locked>"` unhelpfully.

After this change, this just prints the contents of the mutex, like the other smart pointers (and MutexGuard) do.

MutexGuard had this problem too: rust-lang#57702
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