Hi

I am maintaining an application that I wrote a long time ago, in c++. I am facing an issue now in that a library I use has changed the signature of one of its functions. So the code I have builds on ubuntu (ubuntu has an old version of this library in its repos), but it does not build on archlinux (archlinux is bleeding edge). If I fix the code on archlinux, it breaks on ubuntu.

I have read that you can achieve that some defines can be created by the automake tool, depending on the version of the library that I could use in my c++ code. The way I imagine it is that I run ./configure, then it will detect the version of the library, will decide whether it is old or new and then it will define constants. So in my c++ code I can do this:

#ifdef NEWLIBRARY
libfunction(1,2,3); // new signature
#else
libfunction(1,2); // old signature
#endif

Could someone please describe how it works, and could you please give me a few pointers like an example that does this or some keywords that can be used in configure.ac to achieve this?

Thank you and best regards,
Jozsef

In general you can use AC_DEFINE to pass information from configure into your code.

But usually, a library should have some way of getting the version from the code.

Also, note that

Hi

Thank you for your answer.

That is a great approach! But where do I start? How does this work?

Thank you again,
Jozsef

Hi.

You can write a simple check to test if it compiles with your library successfully. Look here.

Hi firstfire,

Using the page you have given I have solved it with versioning. Possibly the compiling thing would be a bit more robust, but for this, for now it does not matter.

Here are the details, if someone is interested, search for PKG_CHECK_MODULES on this page:
https://sites.google.com/site/jozsef...tents/automake

Also here is a real life example, search for MEDIASTREAMER28:
http://gtalx.svn.sourceforge.net/vie...42&view=markup
and here is the .h file (note that ../../config.h is included):
http://gtalx.svn.sourceforge.net/vie...42&view=markup

BTW I find it amazing that ./configure can try to build small snippets to see if a function is supported on the user's PC. This is the best technology I have seen; automake has grown a lot in my eyes :-)

Thank you very much for your help!
Jozsef

1 members found this post helpful.

You might want to use AC_MSG_WARN or AC_MSG_ERROR for this.