[PATCH] D95849: [FileCheck] Default --allow-unused-prefixes to false

[Fangrui Song via Phabricator via cfe-commits]

MaskRay added a comment.

In D95849#2536559 <https://reviews.llvm.org/D95849#2536559>, @nikic wrote:

> Just to be clear here: Only the small handful where a spelling mistake was fixed were actually bugs. All other unused check prefixes were there for convenience, and are now casualties of this unnecessary crusade. I regret not speaking out against this at the time.

Hi, I think the situation is the converse: most are code smell, only a small handful of tests leverage this property. So far the most convincing usage is something like (a) `--check-prefix=%something` where `%something` can expand to multiple prefixes and (b) a customized tool integrating FileCheck feature which expands to multiple prefixes, some prefixes may be omitted.

Issues include (a) misspelled prefixes (b) bitrot prefixes due to refactoring (c) omitted `-NOT` patterns (e.g. some tests use --check-prefixes=CHECK,CHECK-C for C specific UB and --check-prefixes=CHECK,CHECK-CPP. `CHECK-CPP` was absent but was intended to be a `CHECK-CPP-NOT:`)

I think the good uses of --allow-unused-prefixes=true are much fewer than the opposite.


Repository:
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  https://reviews.llvm.org/D95849/new/

https://reviews.llvm.org/D95849