Fortran compiler max line length options
The Fortran 202x standard raises the individual Fortran source code line limit to 10000 characters. The new limits also include unlimited continuation lines and a maximum statement length of one million characters. These are stated as “hard limits”. As has historically been the case, many compilers continue to allow going beyond the line limit in a line or beyond even ten million characters in a statement. LLVMFlang is explicitly designed without a particular character limit per line.
| Fortran standard | source code line length limit |
|---|---|
| 202x | 10000 |
| 90 | 132 |
| 77 | 72 |
Compiler differences in default maximum source code line length can lead to portability issues. For example, Linux workstations or Linux HPC may default to a GCC Gfortran older than version 14 that has a default Fortran source code line length maximum of 132 characters, which is too short for say generated source code containing a data path on a networked HPC drive.
It’s important to be cognizant of the maximum Fortran line length across compilers as developer laptops often default to a recent Flang or Gfortran that both have effectively unlimited line length.
The maximum line length we experienced with no options follows, as determined experimentally with our Fortran maximum line length test program.