[petsc-users] Compile issue

[Mark Adams]

Result from (cut and paste into) Claude:

## Diagnosis

The compile error is caused by **fixed-form Fortran line truncation at
column 72**. Your file `parstop.F` uses the `.F` extension, which tells
`gfortran` to use **fixed-form** parsing (72-column limit by default).

In PETSc 3.25, the
[`PetscObjectIsNull`](include/petsc/finclude/petscsysbase.h:132) macro
expanded significantly. It is now defined as:

```fortran
#define PetscObjectIsNull(obj) (obj%v == 0 .or. obj%v ==
PETSC_FORTRAN_TYPE_INITIALIZE .or. obj%v == -3)
```

When the preprocessor expands `PetscObjectIsNull(Mdiag)`, the resulting
line is far longer than 72 characters and gets truncated mid-expression,
producing the syntax error. The compiler warnings confirm this:

```
parstop.F:64:72:
Warning: Line truncated at (1) [-Wline-truncation]
```

## Solution: Rename `.F` to `.F90`

**Rename `parstop.F` → `parstop.F90`** (and do the same for any other `.F`
files that use `PetscObjectIsNull`).

Your code is already written in free-form Fortran style (`!` comments, `::`
declarations, `implicit none`), so the `.F` extension is misleading. The
`.F90` extension will:

1. Invoke the C preprocessor (uppercase `F` is preserved)
2. Use **free-form** parsing (132-column default limit)
3. Work with your existing `-ffree-line-length-none` flag, which removes
the line length limit entirely

This is the cleanest fix and requires no code changes — only a file rename.

### Alternative: Keep `.F` and add a compiler flag

If renaming is not feasible, add `-ffixed-line-length-none` to your
`mpif90` flags to remove the 72-column truncation for fixed-form files.

On Thu, May 7, 2026 at 6:26 PM Sanjay Govindjee via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> I am trying to update our code to petsc 3.25.1.  We were previously on
> 3.22.4.  I am running into a compile error that I can not understand.  I
> went through the release notes but can not see what is wrong.  Any
> suggestions will be appreciated.
>
> -sanjay
>
> /Users/sg/petsc/gnu/bin/mpif90 -o parstop.o -c -fPIC -Wall
> -ffree-line-length-none -ffree-line-length-0 -Wno-lto-type-mismatch
> -Wno-unused-dummy-argument -g -O   -I/Users/sg/petsc/include
> -I/Users/sg/petsc/gnu/include -I/opt/X11/include
> -I/Users/sg/Feap/ver87/include -I/Users/sg/Feap/ver87/modules
> -I/usr/local/include -J/Users/sg/Feap/ver87/modules       parstop.F
> parstop.F:64:72:
>
>    64 |       if(.not.PetscObjectIsNull(Mdiag)) then
>       |
>      1
> Warning: Line truncated at (1) [-Wline-truncation]
> parstop.F:64:70:
>
>    64 |       if(.not.PetscObjectIsNull(Mdiag)) then
>       |
>    1
> Error: Syntax error in IF-clause after (1)
> parstop.F:66:9:
>
>    66 |       endif
>       |         1
> Error: Expecting END SUBROUTINE statement at (1)
> parstop.F:68:72:
>
>    68 |       if(.not.PetscObjectIsNull(Msqrt)) then
>       |
>      1
> Warning: Line truncated at (1) [-Wline-truncation]
> parstop.F:68:70:
>
>    68 |       if(.not.PetscObjectIsNull(Msqrt)) then
>       |
>    1
> Error: Syntax error in IF-clause after (1)
> parstop.F:70:9:
>
>    70 |       endif
>       |         1
> Error: Expecting END SUBROUTINE statement at (1)
>
> The subroutine is super simple:
>
> #     include   <petsc/finclude/petscksp.h>
>       use                       petscksp
>       use                       pfeapc
>       implicit   none
>
> #     include   "pfeapb.h"
>
>       PetscErrorCode ierr
>
>       logical     :: eflag
>
>       save
>
> !     Close out PETSc matrices
>       if(.not.PetscObjectIsNull(Kmat)) then
>         call MatDestroy(Kmat, ierr)
>       endif
>
>       if(.not.PetscObjectIsNull(Pmat)) then
>         call MatDestroy(Pmat, ierr)
>       endif
>
>       if(.not.PetscObjectIsNull(Mmat)) then
>         call MatDestroy(Mmat, ierr)
>       endif
>
>       if(pfeap_dstr) then
>         call KSPDestroy(kspsol, ierr)
>       endif
>
> !     Close out PETSc vectors
>       if(.not.PetscObjectIsNull(Mdiag)) then
>         call VecDestroy(Mdiag, ierr)
>       endif
>
>       if(.not.PetscObjectIsNull(Msqrt)) then
>         call VecDestroy(Msqrt, ierr)
>       endif
>
> The custom module pfeapc contains the objects:
>
>       module pfeapc
> #     include   <petsc/finclude/petscksp.h>
>       use                       petscksp
>       implicit none
>
>       Vec          :: rhs, sol, xvec
>       Vec          :: yvec, zvec
>       Vec          :: Mdiag, Msqrt
>       Mat          :: Kmat, Mmat, Pmat
>       KSP          :: kspsol
>       end module pfeapc
>
>
>
> ------
>
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