[llvm-dev] Getting rid of "%T" expansions

Kuba Mracek via llvm-dev llvm-dev at lists.llvm.org
Tue Aug 8 17:02:02 PDT 2017

Hi llvm-dev,

In <https://reviews.llvm.org/D35396 <https://reviews.llvm.org/D35396>>, several folks agreed that %T is a generally bad idea and should be removed, because it causes randomly flaky tests due to name collisions.  This is a heads-up that I have patches to remove uses of %T throughout LLVM, Clang and compiler-rt ready to commit.  Unless someone objects, I'll land them in a few days.


> On 8 Aug 2017, at 16:57, Justin Bogner <mail at justinbogner.com> wrote:
>> kubamracek created this revision.
>> Herald added subscribers: kbarton, eraman, javed.absar, nemanjai,
>> sdardis, mehdi_amini.
>> The `%T` lit expansion expands to a common directory shared between
>> all the tests in the same directory, which is unexpected and
>> unintuitive, and more importantly, it's been a source of subtle race
>> conditions and flaky tests.  In https://reviews.llvm.org/D35396, it
>> was agreed that it would be best to simply ban `%T` and only keep
>> `%t`, which is unique to each test.  When a test needs a temporary
>> directory, it can just create one using `mkdir %t`.
>> This patch removes `%T` in llvm.
> The patch itself (and the equivalent ones for the other repos) is
> obvious enough to commit without review if we're all agreed to get rid
> of %T.
> Please send a note to llvm-dev about getting rid of %T though, just in
> case someone opposes for some reason and to avoid surprising out-of-tree
> folks.
>> Repository:
>>  rL LLVM
>> https://reviews.llvm.org/D36495

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