Cyclic dependency when using extern symbols from libraries

Learnit · 05-04-2010, 06:28 AM

I have a shared library (built from C++ code) and a separate C program which calls (extern) functions from the said library.

Also one of the functions in that library needs to call a function in this C program by declaring it 'extern'. This sort of creates a cyclic dependency.

I am getting "unresolved references" error, as expected. How can I get this resolved in the best possible way?

Sergei Steshenko · 05-04-2010, 09:31 AM

Quote:

Originally Posted by Learnit

I have a shared library (built from C++ code) and a separate C program which calls (extern) functions from the said library.

Also one of the functions in that library needs to call a function in this C program by declaring it 'extern'. This sort of creates a cyclic dependency.

I am getting "unresolved references" error, as expected. How can I get this resolved in the best possible way?

In 'man ld' read about '--start-group', '--end-group'.

Learnit · 05-05-2010, 07:18 AM

>

Quote:

Originally Posted by Sergei Steshenko

In 'man ld' read about '--start-group', '--end-group'.

Thanks for the info.
Looks like it is indeed better to re-factor the code to avoid cyclic dependency.

ta0kira · 05-06-2010, 07:26 PM

You shouldn't have that problem if you enclose the declaration of the function in the C++ library with extern "C" {}, then have the executable link to the library. It also matters where you put the library on the command line during linking.
Kevin Barry