For the last week, I have been fighting against the GNU Compiler Collection and MJPEG Tools. Seems that there are two major bugs in GCC 4.1.2 20070110, both related to C++ code.
One is a visibility support bug, where the compiler will erroneously mark visible symbols hidden, and the other is a templating bug where redefinitions will cause an Internal Compiler Error. While the first bug would likely have caused my KDE builds to be broken, the second was blocking building kipi-plugins, since mjpegtools is a dependancy on it and does some strange redefinitions to work around a bug in the GNU Debugger.
Happily, after updating GCC to the 20070305 revision (which techinically updated us to the unofficial 4.1.3 release of GCC) mjpegtools and others seem to build as they should.