converting a 700,000+ line Fortran 77 plus 50,000+ line C++ program to C++, part 1

[Lynn McGuire]

We are converting a 700,000+ Fortran 77 lines of code plus 50,000+ C++
lines of code engineering software product to C++. With all that code,
we produce four Win32 EXEs and three Win32 DLLs. My goal is to add four
Win64 EXEs and three Win64 DLLs to the product with the same
capabilities as the Win32 versions (console, windowed, Excel callable,
Excel embeddable). Plus support for Unicode named files and Unicode
file paths.

I am using a customized version of f2c at the moment to automate 60% to
80% of the conversion from F77 to C++. I have added support for
logical*8, changed the output file from *.c to *.cpp, added an include
for the Fable fem.hpp template library, removed the trailing underscores
from the subroutine and common block names, removed the ftnlen arguments
from the character arguments, converted all F77 comments to the //
instead of the /* */, and a few other items. If desired, I am willing
to post a copy of my modified f2c on my website with the source code.
https://netlib.org/f2c/
https://en.wikipedia.org/wiki/F2c

f2c does not get me totally there. The Fortran character strings were
poorly handled so they will probably needed fixing for proper sizing and
alignment. The i/o code is crap so I take the original F77 i/o code and
translate it by hand. The arrays in the argument list are still based
at an index of one so I convert those to base index of zero by hand.
All of the local and common block arrays were converted to a base index
of zero by f2c. I add the new *.cpp file to my Visual Studio project.
I then add the new function prototypes to my prototypes.h file and I add
any new common block structures to my commons.h file. I then compile
and fix until I get a clean compile.

I have converted over 8,000 lines of F77 code to C++ now. Several dozen
subroutines and several dozen common blocks. Most are compiling cleanly
in Visual C++ 2015. My limited testing is working well and I will
expand my testing when I hit 15,000 or 20,000 lines of F77 code
converted. I hoping to get a complete build of the smaller of the Win32
DLLs by the end of the year and a full build by next June. One of my
programmers thinks that we will be lucky to get a complete build by late
2024.

Lynn

[Chris M. Thomasson]

Is the code modular so you can port and test just a part of it?

[Lynn McGuire]

Somewhat. And yes, that is what I am doing. Port for a while and then
test. Port for a while and then test. I have already completed the
first cycle. No showstoppers.

Lynn

[Richard]

[Please do not mail me a copy of your followup]

Tim Rentsch <tr.1...@z991.linuxsc.com> spake the secret code
<86v8o9h...@linuxsc.com> thusly:

>Lynn McGuire <lynnmc...@gmail.com> writes:
>
>> We are converting a 700,000+ Fortran 77 lines of code plus 50,000+ C++

>> lines of code engineering software product to C++. [...]
>
>Which makes the posting not topical for comp.lang.c.

I'm sure you're just drowning in messages over there compared to say,
1992 usenet traffic.
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[Tim Rentsch]

legaliz...@mail.xmission.com (Richard) writes:

> Tim Rentsch <tr.1...@z991.linuxsc.com> spake the secret code
> <86v8o9h...@linuxsc.com> thusly:
>
>> Lynn McGuire <lynnmc...@gmail.com> writes:
>>
>>> We are converting a 700,000+ Fortran 77 lines of code plus 50,000+ C++
>>> lines of code engineering software product to C++. [...]
>>
>> Which makes the posting not topical for comp.lang.c.
>
> I'm sure you're just drowning in messages over there compared to say,
> 1992 usenet traffic.

I'm surprised to see this kind of a posting coming from
you.