To support the FX's opinion, on i686-apple-darwin9 building ligfortran now fails with:
...
libtool: compile: /opt/gcc/i686-darwin/./gcc/xgcc -B/opt/gcc/i686-darwin/./gcc/ -B/opt/gcc/gcc4.4w/i686-apple-darwin9/bin/ -B/opt/gcc/gcc4.4w/i686-apple-darwin9/lib/ -isystem /opt/gcc/gcc4.4w/i686-apple-darwin9/include -isystem /opt/gcc/gcc4.4w/i686-apple-darwin9/sys-include -DHAVE_CONFIG_H -I. -I../../../../gcc-4.4-work/libgfortran -I. -iquote../../../../gcc-4.4-work/libgfortran/io -I../../../../gcc-4.4-work/libgfortran/../gcc -I../../../../gcc-4.4-work/libgfortran/../gcc/config -I../../.././gcc -D_GNU_SOURCE -std=gnu99 -Werror -Wall -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wextra -Wwrite-strings -fcx-fortran-rules -g -O2 -m64 -MT fbuf.lo -MD -MP -MF .deps/fbuf.Tpo -c ../../../../gcc-4.4-work/libgfortran/io/fbuf.c -fno-common -DPIC -o .libs/fbuf.o
cc1: warnings being treated as errors
../../../../gcc-4.4-work/libgfortran/io/fbuf.c: In function 'fbuf_seek':
../../../../gcc-4.4-work/libgfortran/io/fbuf.c:160: error: comparison between signed and unsigned
make[6]: *** [fbuf.lo] Error 1