translation - Conversion of Fortran 77 code to C++

Question

Has anyone converted a large (ours is 550,000 lines) program of Fortran 77 code to C++ ? What pitfalls did you run into ? Was the conversion a success ? Did you use a tool like for_c ( http://www.cobalt-blue.com/fc/fcmain.htm ) ? Was the resulting C++ code significantly faster or slower ?

Answer 1

This adds to EvilTeach's advice. Keep in mind that it's fairly easy to link Fortran 77 and C/C++ code, so you can convert parts of your application incrementally and link them together with the old parts. You'll have to think about all the usual fortran/c discrepancies (row/column-major arrays, array indexing, etc.) if you do this, but it would save you the pain of debugging your entire auto-translated codebase at once.

There are many large hybrid codes like this at the national (DOE) labs, which have a significant investment in old Fortran code. If you go this route, you might consider using Babel, which was developed to allow components to be shared between C, C++, Fortran, Fortran90, Python and Java all in the same app. The motivation for this at the labs is tying together physics models built by different teams for really large simulations, but you might find it useful for transitioning your code, too. It's actively maintained and used on a lot of projects, though it might be a bit too complex for what you're trying to do.