I've had a look at the config.log (see below). It seems to be returning yes
to the isinf check despite warnings. So port/isinf.c does not get compiled
on subsequent make.
configure:14213: checking for isinf
configure:14235: gcc -o conftest -O2 -Wall -Wmissing-prototypes
-Wpointer-arith
-Winline -Wdeclaration-after-statement -Wendif-labels -fno-strict-aliasing
-I/
usr/local/include conftest.c -lz -lreadline -ltermcap -lrt -lresolv -lgen
-lso
cket -lnsl -ldl -lm >&5
conftest.c: In function 'main':
conftest.c:93: warning: implicit declaration of function 'isinf'
conftest.c:93: warning: unused variable 'res'
configure:14241: $? = 0
configure:14245: test -z
|| test ! -s conftest.err
configure:14248: $? = 0
configure:14251: test -s conftest
configure:14254: $? = 0
configure:14266: result: yes