tlug: Calling C procedures from FORTRAN

["Stephen J. Turnbull" <turnbull@example.com>]

>>>>> "VR" == Venkatesh Raghavan <raghavan@example.com> writes:

    VR> I am writing a FORTRAN program that calls C procedures. I am
    VR> using g77 and gcc compilers.  By default the g77 compiler
    VR> appends an _(underscore) to function and subroutine names. For
    VR> example my program call a C procedure as follows; CALL CPROC()

    VR> and I have to name the C procedure as cproc_()

Does this actually work?  I thought FORTRAN and C had different
calling conventions.  That's what those underscores are for,
preventing you from accidentally linking incompatible call sequences.

    VR> Is there any way/option for suppressing this addition of
    VR> underscore in FORTRAN so that C procedures can be called
    VR> directly (without adding an underscore).

In C++, if FORTRAN linkage is supported, you can do the following

#ifndef NAG_WRAPPER
#define NAG_WRAPPER
extern "fortran" {

/* prototypes for NAG routines go here */

}

This automatically generates the necessary thunks to make sure the
arguments are in the right order and alignment and so on.  I don't
know how you would do this in FORTRAN to call C.

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