On 28 Jul 2010, at 21:49, Mike Solomon wrote:
Hey guile users,
Trying to compile the simple example bessel.c from
Writing-Guile-Extensions.html (renamed bessel.cc because I'm using g+
+), I
encountered the following error:
bessel.cc: In function 'void init_bessel()':
bessel.cc:13: error: invalid conversion from 'scm_unused_struct*
(*)(scm_unused_struct*)' to 'scm_unused_struct* (*)(...)'
bessel.cc:13: error: initializing argument 5 of 'scm_unused_struct*
scm_c_define_gsubr(const char*, int, int, int, scm_unused_struct* (*)
(...))'
The SCM type is a pointer to an undefined C type - C hack, which
clashes with C++. Clever in C, but bad for C++ users.
This even comes up when I put everything in extern "C" { ... }. I
have seen
other postings on the net for other software (lilypond, swig) that
speaks of
the same issue, and some suggest that it is a problem with g++ and not
guile. I'm using powerpc-apple-darwin8-g++-4.0.1 (GCC) 4.0.1 (Apple
Computer, Inc. build 5370)
When you use g++, all stuff is compiled as C++. So use gcc and add c++
libraries when linking.
Then in formally correct C++, main() must be C++. Gcc accepts calling C
++ from C, but attempting to pass an exception through a C function is
converted to a termination exception.
So I wrote a C++ function scm::init_guile() calling scm_init_guile()
and other stuff that needs to be initialized. Then
int main(int argc, char** argv) {
init_guile();
try {
...
}
...
}
Then write a header bessel.h
#ifndef BESSEL_H
#define BESSEL_H
/* Copyright ...
Free Software Foundation GNU General Public License <http://www.gnu.org/licenses/
>
*/
#ifdef __cplusplus
extern "C" {
#endif
void init_bessel();
...
#ifdef __cplusplus
} // extern "C"
#endif
#endif BESSEL_H
The file bessel.c is compiled as C, but your C++ files include bessel.h.
Hans
