[flang-commits] [clang] [flang] [flang] Reject oversized -ffixed-line-length values (PR #229972)

[Eugene Epshteyn via flang-commits]

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@@ -16,6 +17,7 @@
 ! RUN: %flang_fc1 -E -fno-reformat %S/Inputs/fixed-line-length-test.f  2>&1 | FileCheck %s --check-prefix=DEFAULTLENGTH
 ! RUN: not %flang_fc1 -E -fno-reformat -ffixed-line-length=-2 %S/Inputs/fixed-line-length-test.f  2>&1 | FileCheck %s --check-prefix=NEGATIVELENGTH
 ! RUN: not %flang_fc1 -E -fno-reformat -ffixed-line-length=3 %S/Inputs/fixed-line-length-test.f  2>&1 | FileCheck %s --check-prefix=INVALIDLENGTH
+! RUN: not %flang_fc1 -E -fno-reformat -ffixed-line-length=4294967296 %S/Inputs/fixed-line-length-test.f  2>&1 | FileCheck %s --check-prefix=OVERFLOWLENGTH
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eugeneepshteyn wrote:

(This comment was generated with the help of AI)

4294967296 is 2^32, so this test would still pass with a bound of `columns > UINT32_MAX`, which leaves 2147483648 through 4294967295 silently wrapping. Nothing checks that 2147483647 stays accepted either, so `columns >= INT_MAX` would also pass. Please pin both sides of the boundary:

```fortran
! RUN: not %flang_fc1 -E -fno-reformat -ffixed-line-length=2147483648 %S/Inputs/fixed-line-length-test.f  2>&1 | FileCheck %s --check-prefix=BOUNDARY
! RUN: %flang_fc1 -E -fno-reformat -ffixed-line-length=2147483647 %S/Inputs/fixed-line-length-test.f  2>&1 | FileCheck %s --check-prefix=UNLIMITEDLENGTH

! BOUNDARY: invalid value '2147483648' in 'ffixed-line-length=', value must be '2147483647' or smaller
```

The 2147483648 line needs its own prefix because `OVERFLOWLENGTH` spells out `4294967296`. Without this PR, `-ffixed-line-length=2147483648` exits 0 with empty preprocessed output, so the new line fails there. `2147483647` matches `UNLIMITEDLENGTH` with and without the PR.

https://github.com/llvm/llvm-project/pull/229972