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(automake.info)Mixing Fortran 77 With C and C++

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Mixing Fortran 77 With C and C++
--------------------------------

   Automake currently provides _limited_ support for creating programs
and shared libraries that are a mixture of Fortran 77 and C and/or C++.
However, there are many other issues related to mixing Fortran 77 with
other languages that are _not_ (currently) handled by Automake, but
that are handled by other packages(1).

   Automake can help in two ways:

  1. Automatic selection of the linker depending on which combinations
     of source code.

  2. Automatic selection of the appropriate linker flags (e.g. `-L' and
     `-l') to pass to the automatically selected linker in order to link
     in the appropriate Fortran 77 intrinsic and run-time libraries.

     These extra Fortran 77 linker flags are supplied in the output
     variable `FLIBS' by the `AC_F77_LIBRARY_LDFLAGS' Autoconf macro
     supplied with newer versions of Autoconf (Autoconf version 2.13 and
     later).  *Note Fortran 77 Compiler Characteristics:
     (autoconf)Fortran 77 Compiler Characteristics.

   If Automake detects that a program or shared library (as mentioned in
some `_PROGRAMS' or `_LTLIBRARIES' primary) contains source code that
is a mixture of Fortran 77 and C and/or C++, then it requires that the
macro `AC_F77_LIBRARY_LDFLAGS' be called in `configure.in', and that
either `$(FLIBS)' or `@FLIBS@' appear in the appropriate `_LDADD' (for
programs) or `_LIBADD' (for shared libraries) variables.  It is the
responsibility of the person writing the `Makefile.am' to make sure
that `$(FLIBS)' or `@FLIBS@' appears in the appropriate `_LDADD' or
`_LIBADD' variable.

   For example, consider the following `Makefile.am':

     bin_PROGRAMS = foo
     foo_SOURCES  = main.cc foo.f
     foo_LDADD    = libfoo.la @FLIBS@
     
     pkglib_LTLIBRARIES = libfoo.la
     libfoo_la_SOURCES  = bar.f baz.c zardoz.cc
     libfoo_la_LIBADD   = $(FLIBS)

   In this case, Automake will insist that `AC_F77_LIBRARY_LDFLAGS' is
mentioned in `configure.in'.  Also, if `@FLIBS@' hadn't been mentioned
in `foo_LDADD' and `libfoo_la_LIBADD', then Automake would have issued
a warning.

How the Linker is Chosen

   ---------- Footnotes ----------

   (1) For example, the cfortran package
(http://www-zeus.desy.de/~burow/cfortran/) addresses all of these
inter-language issues, and runs under nearly all Fortran 77, C and C++
compilers on nearly all platforms.  However, `cfortran' is not yet Free
Software, but it will be in the next major release.