First, I think the ctags/etags example in the docs are wrong, at least in the more complex example that describes de-ANSI-fication. In both the examples the input should be coming from a ._c file and the resulting file should be a ._o file. Perhaps better, a combined example that uses $U? And the example does not handle non-srcdir builds properly.
Next, I'm currently building libfoo.a, which has a decent number of source modules. I now have to build two libraries, libfoo.a and libfoosim.a, where the only difference between the two libraries is that bar.c is compiled "normally" for libfoo.a, but for libfoosim.a I need to also supply -DSIM when compiling bar.c . As you might imagine, I'm doing this in an environment that must support de-ANSI-fication. Ideas? Harlan