[CMake] Mixing C++ and Fortran

[Bill Hoffman]

Honest Guvnor wrote:
> I am building a program with a C++ main (WxWidgets) and linking with C
> and Fortran libraries. My problem is that on each platform I am
> currently having to find the basic Fortran library (e.g. libg2c for
> g77) and include it explicitly in the target_link_libraries list.
> 
> I have tried adding a dummy fortran file to the list of C++ files to
> force it know about Fortran and get prompted to declare the
> linker_language property. Setting this to C++ results in no change. I
> have downloaded and installed the current version 2.4.8 with no
> change. I have tried OSX and Linux with the same result. I have mixed
> Fortran and C in another program without problems. A mix of C++ and C
> was working in this program until the addition of the Fortran
> libraries.
> 

Well, you are sort of stuck...

You can change the default linker language for any target with this 
property:

SET_TARGET_PROPERITES( <tgt> PROPERTIES LINKER_LANGUAGE CXX)

Could be:

SET_TARGET_PROPERITES( <tgt> PROPERTIES LINKER_LANGUAGE Fortran)

However, you will have the same issue with C++ libraries being missing 
if you change the linker language to Fortran.  Fortran and C are not 
really an issue since the c runtime is always there.   However, Fortran 
and C++ are an issue...

You might be able to put the fortran stuff in a shared library and have 
the fortran runtime pulled in that way.   You could write some fancy 
find_* fortran stuff using try-compile that finds out the fortran run 
time library.

-Bill