| Issue |
202815
|
| Summary |
[Flang] preprocessor bug with OpenMP sentinels in fixed-format source
|
| Labels |
flang
|
| Assignees |
|
| Reporter |
scivision
|
When fixed-format .F source code with OpenMP directives exists, but OpenMP isn't used, Flang isn't preprocessing the source code correctly. This impacts CMake + Ninja, with the root cause seeming to be a bug in Flang revealed by that common use case.
The bottom of this issue has minimal reproducer code. This occurs across all versions of LLVM Flang I've tried over a couple years.
```sh
src = ""
pp = "flang_mwe-pp.f"
flang -c $src # OK
flang -cpp -E $src -o $pp # emits warning
flang -c $pp # errors
```
### Expected
1. direct compile succeeds
2. preprocess succeeds
3. compile succeds
### Actual
1. Direct compile succeeds.
2. Preprocess gives warning and incorrect syntax generated
3. Compile of preprocessed file fails with unmatched parentheses.
### Problematic Snippet
```fortran
call mysub(a, b
!$ &,dummy&
)
```
The expected source preprocessed is the following. This is like what Gfortran correctly generates.
```fortran
call mysub(a, b
!$ & ,dummy
& )
```
## file "flang_mwe.F"
```fortran
program mwe
call mysub(a, b
!$ & ,dummy
& )
contains
subroutine mysub(a, b, dummy)
real :: a, b
real, optional :: dummy
end subroutine mysub
end program
```
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