autoconf breakage on x86_64.

I don't know the right way to fix this, but something is definitely broken; and something needs to be fixed, one way or the other. The question is what exactly needs to be fixed. Consider something like this: LIBS="-lresolv $LIBS" AC_TRY_LINK_FUNC(res_query, AC_MSG_RESULT(yes), AC_MSG_RESULT(no)) Here's what happens on x86_64: gcc -o conftest -g -O2 -Wall -I.. -I./.. conftest.c -lresolv >&5 /tmp/ccW7EeDX.o(.text+0x7): In function `main': /home/mrsam/src/courier/authlib/configure:5160: undefined reference to `res_query' collect2: ld returned 1 exit status configure:5147: $? = 1 configure: failed program was: [ blah blah blah ] | /* We use char because int might match the return type of a gcc2 | builtin and then its argument prototype would still apply. */ | char res_query (); | int | main () | { | res_query (); | ; | return 0; | } The same exact test on FC1 x86 will work. The reason appears to be that you have to #include <resolv.conf> on x86_64 in order to succesfully pull res_query() out of libresolv.so. You don't need to do this on x86, and the test program generated by AC_TRY_LINK_FUNC does not include any headers, but uses a manual prototype. So, what now?