From: ludo@gnu.org (Ludovic Courtès)
To: guile-user@gnu.org
Subject: Re: gh_new_procedure with c++
Date: Mon, 23 Jun 2008 11:59:17 +0200 [thread overview]
Message-ID: <87lk0w8oay.fsf@gnu.org> (raw)
In-Reply-To: 270252.38285.qm@web26905.mail.ukl.yahoo.com
Hello,
gianluca giorgolo <giorghy@yahoo.it> writes:
> I'm trying to use 'gh_new_procedure' to define a new procedure for Scheme that refers to a c++ function. This function takes more than 0 arguments. But given that the gh_new_procedure is defined as taking a function with no argument, g++ complains about the invalid conversion:
>
> main.cpp:131: error: invalid conversion from ‘scm_unused_struct* (*)(scm_unused_struct*, scm_unused_struct*, scm_unused_struct*, scm_unused_struct*, scm_unused_struct*)’ to ‘scm_unused_struct* (*)()’
> main.cpp:131: error: initializing argument 2 of ‘scm_unused_struct* gh_new_procedure(const char*, scm_unused_struct* (*)(), int, int, int)’
I think it has to be a C function, not a C++ function, i.e., your
function declaration and definition has to be surrounded by `extern "C"
{ ... }'.
This is because the argument to `gh_new_procedure ()' is *not* a
zero-argument function, but a function with *any* number of arguments.
Until the C99 standard (included), "void (* foo) ()" means "pointer to a
function taking any number of arguments"; in C++, it means "pointer to a
function with no arguments". Future C standards will probably follow
C++ on that, as noted in the "Future Language Directions" of C99
(Section 6.11.6):
The use of function declarators with empty parentheses (not
prototype-format parameter type declarators) is an obsolescent
feature.
This means Guile will eventually have to find another solution.
Besides, `gh_new_procedure ()' is deprecated in 1.8; you should use
`scm_c_define_gsubr ()' instead.
Thanks,
Ludovic.
next prev parent reply other threads:[~2008-06-23 9:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-22 22:13 gh_new_procedure with c++ gianluca giorgolo
2008-06-23 9:59 ` Ludovic Courtès [this message]
2008-06-23 11:47 ` Ludovic Courtès
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