Re: linking c code against fortran libraries

[Craig Maloney <cmaloney at physics dot ucsb dot edu>]

Apologies to all who've replied...
There *was* no main symbol in my foo.o because there was no main in foo.c 
(long story).

Either of 
g77  foo.o -lfortlib
or
gcc foo.o -lfortlib -lfrtbegin -lg2c -lm -shared-libgcc

link and run fine.

Thanks again,
Craig

On Thu, 29 Jan 2004, Paul Brook wrote:

> On Wednesday 28 January 2004 5:24 pm, Craig Maloney wrote:
> > Hi all.
> >
> > I have some questions about linking c code against fortran libraries.
> > Suppose I have a code foo.c which calls routines in a fortran library
> > libfortlib.
> >
> > First question:
> > is
> > g77  foo.o -lfortlib
> > equivalent to
> > gcc foo.o -lfortlib -lfrtbegin -lg2c -lm -shared-libgcc
> >
> > or does it actually matter that the compiler was invoked as g77.
> >
> > At any rate, neither of these is successful and give equivalent error:
> > gcc-3.2.1/i686-pc-linux-gnu/libf2c/libF77/main.c: undefined reference to
> > `MAIN__'
> >
> > It was my understanding that linking with g77 was supposed to tie up the
> > stuff so that the entry point into the executable was somewhere in
> > libfrtbegin which then called foo.o:main() after libg2c initialization.
> 
> No. libfrtbegin provides a main() function. This then calls the fortran 
> PROGRAM unit (called MAIN__ internally).
> 
> You have three options:
> 
> - Don't link libfrtbegin, and provide a C main(). The link you quoted 
> describes the things you need to do to ensure the Fortran runtime operates 
> correctly.
> - Link libftrbegin, and rename your C program entry point to MAIN__
> - Link libftrbegin, and write your program entry point in Fortran.
> 
> Depending which you choose you may need to make sure you get the commanline 
> arguments in the correct order.
> 
> > http://gcc.gnu.org/onlinedocs/gcc-3.3.2/g77/Startup-Code.html#Startup%20Code 
> 
> This seems reasonably accurate, it just doesn't mantion that the libg2c main() 
> is actually in libfrtbegin.
> 
> Paul
>