This function builds a simple test project using a combination of
Fortran and C (and optionally C++) to verify that the compilers are
compatible. The idea is to help projects report very early to users
that the compilers specified cannot mix languages.
This is a new FortranCInterface.cmake module to replace the previous
prototype. All module support files lie in a FortranCInterface
directory next to it.
This module uses a new approach to detect Fortran symbol mangling. We
build a single test project which defines symbols in a Fortran library
(one per object-file) and calls them from a Fortran executable. The
executable links to a C library which defines symbols encoding all known
manglings (one per object-file). The C library falls back to the
Fortran library for symbols it cannot provide. Therefore the executable
will always link, but prefers the C-implemented symbols when they match.
These symbols store string literals of the form INFO:symbol[<name>] so
we can parse them out of the executable.
This module also provides a simpler interface. It always detects the
mangling as soon as it is included. A single macro is provided to
generate mangling macros and optionally pre-mangled symbols.
Previously the Fortran test created a single executable containing C,
C++, and Fortran sources. This commit divides the executable into three
libraries corresponding to each language, and two executables testing
Fortran/C only and Fortran/C/C++ together. The result tests more
combinations of using the languages together, and that language
requirements propagate through linking.
This extends the Fortran-to-C interface test to add a C++ source file.
The executable can only link with the C++ linker and with the proper
Fortran runtime libraries. These libraries should be detected by CMake
automatically, so this tests verifies the detection functionality.
This hack was created to help the Fortran test executables link to the
implicit C libraries added by BullsEye. Now that implicit libraries
from all languages are detected and included automatically the hack is
no longer needed.
Brad King
Bill Hoffman
Ken Martin