Zend/SAPI question about conditional compilations

Can I use a build of Zend/SAPI that was built against one sapi type against a different type w/o rebuilding, or are there compile-time conditionals built in to the binaries? If this is not possible, we'd like to modify the SAPI to allow for overriding of the YY_INPUT macro produced by flex to call a callback registered by the SAPI module. This will allow the lexer to pull input data in whatever method is most efficient to the SAPI module. (Cliff and I want this specifically for the apache2filter so that we can pull data straight from the bucket brigade provided in Apache 2.) -aaron