On 11/26/2012 08:02 AM, Nick Bowler wrote: > Hi folks, > > Autoconf defines a macro called AC_PROVIDE_IFELSE, which can allow > one to hook into the AC_REQUIRE machinery in order to do potentially > interesting things. For a specific example, I recently wanted to emit a > (hopefully) helpful warning message if LT_INIT had not been previously > expanded, and it seems that I can do that very easily with something > like: > > AC_PROVIDE_IFELSE([LT_INIT], , [m4_warn([syntax], [blah blah])]) Good question - looks like you found a real hole in the documentation. It looks like AC_PROVIDE vs. AC_PROVIDE_IFELSE should be documented together; and also that m4_provide and m4_provide_if should be documented together. What's more, the manual mentions that macros can call AC_PROVIDE but does not document what it does. > > However, AC_PROVIDE_IFELSE is not described in the Autoconf manual, > which makes me wonder if the macro should be used by packages. The fact > that it's defined at all (as an alias for m4_provide_if) seems to > suggest that it was intended to be used... Yes, the macros are stable and intended to be usable; we're just missing the documentation patch. > > Also, on a related note, AC_PROVIDE is referred to several times in the > Autoconf manual (in a manner that suggests that packages can use it) but > the manual never actually explains what AC_PROVIDE does or how to invoke > it properly. Yep, I just came to the same conclusion after reading just your first paragraph and searching for myself. > > So, are these macros intended to be used by packages? If so, can they > be documented in the manual? Absolutely. Want to help write the patch? -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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