I recently modified a test version of Emacs to use gnulib's vsnprintf module, and found that on my RHEL 5.6 host (which has a working vsnprintf), the gnulib code added quite a bit of of unnecessary work to configure and build vasnprintf.o, printf-parse.o, printf-args.o, and asnprintf.o. None of these object files were needed: they were put into libgnu.a but were not used by anybody.
If an application uses vsnprintf, but does not use vasnprintf directly, then there's no need to configure and build those .o files on hosts that have a working vsnprintf. I'd like to fix gnulib to avoid this work. One way that comes to mind is to modify modules/vsnprintf so that it depends on a new module (modules/vasnprintf-if, say), which acts like modules/vasnprintf but does not put gl_FUNC_VASNPRINTF into configure.ac. Most of the contents of modules/vasnprintf would be moved into modules/vasnprintf-if. Then, gl_REPLACE_VSNPRINTF could invoke gl_FUNC_VASNPRINTF. Similarly for alloca-opt, float, stdint, xsize, memchr, and wchar: all of these modules do configure- and make-time work that can be avoided on hosts like RHEL 5.6, assuming the application needs vsnprintf but not vasnprintf. I think this approach would work for Emacs, but it seems clumsy, and I'm hoping there's a better way.
