Rewrite FortranCInterface module

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.

1 files changed, 4 insertions, 0 deletions

diff --git a/Modules/FortranCInterface/symbol.c.in b/Modules/FortranCInterface/symbol.c.in
new file mode 100644
index 0000000..369fa45
--- /dev/null
+++ b/Modules/FortranCInterface/symbol.c.in
@@ -0,0 +1,4 @@
+const char* @symbol@(void)
+{
+  return "INFO:symbol[@symbol@]";
+}