Eric Blake <ebb9 <at> byu.net> writes: > > which puts the burden back on the user, where calling: > > AS_IF([false], [], [AC_REQUIRE(...)]) > > causes a syntax error. > > If I could get AC_REQUIRE to play nicely with m4_expand, then that would be the > solution - pre-expand the user's text, at which point we then know for certain > whether the expansion is empty. But right now, I don't know how to pull that > trick off.
Here's a thought - right now, AC_REQUIRE is identical to m4_require, and expands to an empty string. What if we instead did: m4_define([AC_REQUIRE], [m4_require($@):;]) which makes every use of AC_REQUIRE output a valid shell command? The ; is necessary, since "AC_REQUIRE(...)dnl" is a common idiom. That only helps one particular case of a macro that used to expand to an empty string, but it is probably the most common case. -- Eric Blake
