FileCheck: strange regexp match behavior on CFI tests

[Mephistophiles]

I encountered CFI test failures in tests similar to compiler-rt/test/cfi/multiple-inheritance.cpp when using a libc implementation that outputs additional debug information.

The issue occurs with FileCheck patterns like:

// RUN: FileCheck -check-prefix=CFI -input-file %s %s
Some string 12
1

CFI: 1
CFI-NOT: {{^2$}}

This test fails, but if 1 is replaced with {{^1$}}, it passes.

Expected Behavior:

• CFI: 1 should match the digit 1 on owns line
• CFI-NOT: {{^2$}} should not find 2 (because in this test there is no string that contains only '2')

Current Behavior:

• CFI-NOT: {{^2$}} pattern incorrectly matches, suggesting that after matching 1.

Questions:

• Is this the expected behavior of FileCheck?

[nikic]

By default CHECK does not match full lines. You can enable that behavior using --match-full-lines.

[Mephistophiles]

By default CHECK does not match full lines. You can enable that behavior using --match-full-lines.

So, should I fix the FileCheck invocation in the CFI tests? (

llvm-project/compiler-rt/test/cfi/simple-fail.cpp

Line 88 in f4f247f

// CFI: 1

)