Recently gcc added precompiled header support. This is mostly useful for C++, but C might benefit in some cases too.
To use it, you make a special `.gch' file by compiling a bunch of .h files. Then you tell gcc to use it when compiling. Automake could usefully automate this. First, when building the .gch file we could do automatic dependency tracking (the process of building this file should support the normal -M flags). Also, if a .gch file is listed in _SOURCES, it would be cool to build this file before trying to build any of the objects associated with the _SOURCES variable. (This could be generalized to all .h files, perhaps, to let us reduce the scope of BUILT_SOURCES.) This could be implemented by adding a new dependency for each .o file. There would also have to be a way to disable .gch support for non-gcc compilers. Tom