The header file ap_config_auto.h is a bit flawed. It defines PACKAGE_NAME and PACKAGE_VERSION, and similar constants. If one would like to compile their own module, one could write something like: #ifdef HAVE_CONFIG_H #include <config.h> #endif #include <httpd.h> #include <http_config.h> #include <http_protocol.h> #include <ap_config.h> This would give compiler warnings (not errors) about PACKAGE_NAME being re-defined. This is a bit sloppy and certainly not necessary. Hardly any C program defines PACKAGE_NAME and similar constants outside config.h, and header files should certainly not re-define them. It would be better to have this in ap_config_auto.h: #ifndef PACKAGE_BUGREPORT # define PACKAGE_BUGREPORT "" #endif So it's not very critical, but it's also not nice to cause warnings that need not be caused.