[PATCH] D60392: FileCheck [12/12]: Support use of var defined on same line

Wed May 13 08:05:29 PDT 2020

thopre added a comment.

In D60392#2033357 <https://reviews.llvm.org/D60392#2033357>, @jhenderson wrote:

> I don't have a clear solution to the problems you're describing, but I have already run into one or two places where I wanted the behaviour of being able to use a numeric variable on the same line it was defined. CHECK-SAME is a valid workaround, but has its own issues (for example, it doesn't inherently ensure the next match starts immediately after the previous one, and is just simply more verbose). My instinct is that the right approach is to ignore the constraint initially, match a number, and then verify that it is the right number, failing if not, without further search attempts. I think it's relatively easy to workaround that issue in most cases, with additional checks elsewhere, although I can't be positive that is the case.

What worries me is the effect on a CHECK-NOT directive since it could lead to the directive being fulfilled in a case where the intent was to forbid it. Consider the following:

  CHECK-NOT: [[#VAR:]] [[#VAR+1]]

Say the author of the test was looking a a bug where the output being checked was 10   11   14. The test would pass. Now if the bug wasn't fully fixed, perhaps this doesn't happen anymore but we can have cases like 10   13   14. The above directive will turn into ([[:digit:]]+) ([[:digit:]]+) which will match 10 and 13 and will then check if they are consecutive numbers. They are not and thus the CHECK-NOT is satisfied even though there was   13   14 later on the line. Of course here we could retry after the first number matched but that doesn't work in the general case where regex can appear anywhere (e.g. #VAR: {{.*}} #VAR+1 where the input is now 10   8   11).

Perhaps the solution is to forbid using a variable defined on the same line for a CHECK-NOT directive? In all other cases we'll get a false negative (directive not satisfied) instead of a false positive (directive satisfied).

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https://reviews.llvm.org/D60392