Hi guys....I've spent the whole night trying to figure out about this
question. Please help me if you have any clue. Thanks a lot.

The code is very easy. I'm trying to call a fortran function from C.

The code is as follow:

=========C code=========
#include "stdio.h"

extern float r_ (int * d, float *b);

main ()
{
float a = 1.5, b = 1.05, c = 1;
int d = 2;
c = r_ (&d, &b);
printf ("%%f\n", c);
}

==========Fortran Code===========
real function r(m,t)
integer m
real t

On May 5, 10:55 pm, K-9 gmail.com> wrote:

Good question. I'm trying to use g77 because i'm trying to develop
some fortran77-only code. Of course yes i can go with gfortran. I was
just curious to see the reason.

Thanks.

On May 5, 11:26 pm, e p chandler juno.com> wrote:

In article <5065dea5-eb9e-4b0c-9413-04252b88eff0@34g2000hsh.googlegroups.com>,
K-9 gmail.com> wrote:

Check out the f2c-abi. On x86 and x86-64, this is the difference between
g77 and gfortran's calling conventions.

-- greg

e p chandler wrote:

I don't remember the exact set of options required, but I believe one
can make gfortran use the g77 calling convention. I don't think it's
the default, though.

In article <482096a8$0$9832$a726171b@news.hal-pc.org>,
Craig Powers hal-pc.org> writes:

-ff2c is the option. g77's calling convention is actually the
f2c calling convention bacause Craig Burley re-used the f2c
run-time library.

lindahl@pbm.com (Greg Lindahl) writes:

In that case, does this declaration fix the OP's code:

extern double r_ (int * d, float *b);

i.e., in the C code, declare the return value to be double, but
maintain the "real function r(m,t)" definition in the Fortran code
compiled by g77.

Chip

K-9 wrote:

Real functions have always been bizarre for reasons I never quite
understood, but which had to do with there being no standard convention
for how the return value is passed. Even in otherwise compatible object
files made by two different compilers they might not work.

At the point that I discovered this particular little weirdity, I just
gave up using them in mixed language programming - it wasn't worth the
hassle of never knowing if they would work.

Catherine.

e p chandler wrote:

Yes, there is. For F77 code g77 is by far faster than gfortran. I found
a factor of about three for one oy my simulation programs (I can't
remember which, but most probably something with N-body calculations).
If compiled with g77 it took about 20 seconds for a test run. The same
code, but compiled with gfortran, needed about 70 sec. As far as I
remebmer, the ratio was not really better with optimisation options
(BTW, what is the reason for that?).

Ingo

On May 13, 2:09 pm, Ingo Thies wrote: