libstdc++.so.x issue

[Shen Wu]

Hi,

We have a SDK type of application using C++ and built in gcc/g++. We provided *.so to our customers so that they can link their applications with it. We noticed that gcc standard library so file (libstdc++.so.x) keeps changing the version number. In gcc 3.0.4 it is libstdc++.so.3, in gcc 3.1 it is libstdc++.so.4 and now in gcc 3.2 it becomes libstdc++.so.5. Every time when a new version of gcc comes out, we have to rebuild our SDK. Otherwise, our SDK will not work for the machine with new gcc installed.

In term of glibc, the Linux vendors and GNU always do libc.so.6 -> libc-2.x.x.so. Therefore we do not have to rebuild our application as long as the new glibc backward compatible.

Anyone know what is the reason GNU doing this? 
What is the positioning of the major Linux vendors and GNU on this? 
Do they expect users rebuild their applications very time they update the OS/GCC?
Where can I find the information on this?

Thanks

Shen