(Sorry, originally sent this reply only to Zack. email is hard :) ) > On Mar 14, 2021, at 11:57 AM, Zack Weinberg <zackw@xxxxxxxxx> wrote: > > On Sat, Mar 13, 2021 at 4:53 PM Dan Mahoney (Gushi) > <danm@xxxxxxxxxxxxxxx> wrote: >> >> Hey there, >> >> I've just quelled a bunch of obselscence warnings for 2.70/2.71 in >> OpenDMARC, so now I'm looking at the rest of it. >> >> In our project, we're doing the following to detect if we need -lresolv >> (bottom of mail). > ... >> So there seems to be a good way to quiesce the need for resolv.h but not >> -lresolv. This feels disjoint. Am I missing something? > > There isn't a built-in macro for -lresolv/-lbind, but you could > express MTR's construct more concisely with AC_SEARCH_LIBS: > > AC_HEADER_RESOLV > > AC_SEARCH_LIBS([res_query], [-lresolv -lbind], [], > [AC_SEARCH_LIBS([__res_query], [-lresolv -lbind], [], > [AC_MSG_ERROR([No resolver library found])])]) > > AC_SEARCH_LIBS([dn_expand], [-lresolv -lbind], [], > [AC_MSG_ERROR([No resolver library found])]) > > And then you could follow that up with a single AC_COMPILE_IFELSE with > the test program you're using today, to verify that everything you > need is available. I can’t find a simple way to get autoconf to easily detect something like: I want res_mkquery, which doesn’t exist in libresolv. (What exists in libresolv is __res_mkquery). What points res_mkquery to __res_mkquery is a preprocessor #DEFINE macro in resolv.h. Autoconf gives you no builtin to resolve those macros to their real function names. Or to detect them as though they’re functions with AC_SEARCH_LIBS. If there’s a way to simply include resolv.h and still use *just* macros without doing an AC_COMPILE_IFELSE? Another feature I’d like to see is: “here’s all the resolver functions I use in my code (and maybe their __versions because of the issue above), do I need libresolv for *any* of them?" If so, define -lresolv”, But without having to do the nested block above for each function. -Dan
