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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.lang.fortran
Subject: Re: how do you send a fortran character string from GCC to GFortran ?
Date: Fri, 3 Jan 2025 00:30:39 -0000 (UTC)
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On Thu, 2 Jan 2025 02:27:54 -0600, Lynn McGuire wrote:

> How do you send a fortran character string from GCC to GFortran ?

Seems like trying to call Fortran routines from C is not quite 
straightforward. Looking at the (draft?) Fortran 2023 spec, page 514 says:

    In a reference from C to a Fortran procedure with an interoperable
    interface, a C actual argument shall be the address of a C
    descriptor for the intended effective argument if the
    corresponding dummy argument interoperates with a C formal
    parameter that is a pointer to CFI_cdesc_t.

The following section (page 516 onwards) defines these “C descriptors”. Or 
alternatively (back to page 514), you might need to declare your Fortran 
routine with the “BIND(C)” attribute.