binary incompatibility of code compiled w/ gcc 2.96 and 3.0.4

[Stephen J Fromm]

I'm writing C/C++ code for a CGI program.

Things were working fine---code ran successfully on my PC (under Linux) and
the webhosting service (also running Linux).  Then I upgraded gcc from 2.96
to 3.0.4.  Now executables run fine on my PC, but not on the webhosting
service.

If I compile with 2.96 instead, things execute fine at the hosting service.

They say they use gcc 2.96.  I checked, and they use the same version of
glibc that I do (2.2.4).

Finally, when I compile code on my PC using either gcc 2.96 or 3.0.4, it
runs fine.

Why is this?  And is there a way to run the gcc-3.0.4 binaries on the
webhosting site, or will I be forced to use gcc-2.96?  (I'd rather not do
the latter, as 2.96 doesn't seem to properly deal with C++ namespaces.)

TIA,

sjfromm