Seems to me that http://gcc.gnu.org/ml/gcc-cvs/2009-11/msg00648.html might cause this:
/usr/local/src/trunk/objdir/./prev-gcc/xgcc -B/usr/local/src/trunk/objdir/./prev-gcc/ -B/usr/local/gnu/i686-pc-cygwin/bin/ -B/usr/local/gnu/i686-pc-cygwin/bin/ -B/usr/local/gnu/i686-pc-cygwin/lib/ -isystem /usr/local/gnu/i686-pc-cygwin/include -isystem /usr/local/gnu/i686-pc-cygwin/sys-include -c -g -O2 -gtoggle -DIN_GCC -W -Wall -Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wmissing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Werror -Wold-style-definition -Wc++-compat -fno-common -DHAVE_CONFIG_H -I. -I. -I../../gcc/gcc -I../../gcc/gcc/. -I../../gcc/gcc/../include -I../../gcc/gcc/../libcpp/include -Iyes/include -I../../gcc/gcc/../libdecnumber -I../../gcc/gcc/../libdecnumber/dpd -I../libdecnumber -DCLOOG_PPL_BACKEND \ ../../gcc/gcc/config/i386/i386.c -o i386.o cc1: warnings being treated as errors ../../gcc/gcc/config/i386/i386.c: In function 'avx_vpermilp_parallel': ../../gcc/gcc/config/i386/i386.c:24542:24: error: comparison between signed and unsigned integer expressions make[3]: *** [i386.o] Error 1 make[3]: Leaving directory `/usr/local/src/trunk/objdir/gcc' make[2]: *** [all-stage2-gcc] Error 2 make[2]: Leaving directory `/usr/local/src/trunk/objdir' make[1]: *** [stage2-bubble] Error 2 make[1]: Leaving directory `/usr/local/src/trunk/objdir' Windows XP Pro/SP3 cygwin Intel Core2 Duo t9...@2.80ghz system with packages: binutils 2.19.51-1 2.19.51.20090704 bison 2.3-1 2.3 cloog-ppl 0.15.3-1 cygwin 1.7.0-65 dejagnu 20021217-2 1.4.2.x expect 20030128-1 5.26 gcc4-ada 4.3.4-1 gcc4-core 4.3.4-1 gcc4-g++ 4.3.4-1 gmp 4.3.1-3 libcloog-devel 0.15.3-1 libgmp-devel 4.3.1-3 libmpc-devel 0.8-1 libmpfr-devel 2.4.1-4 libppl 0.10.2-1 make 3.81-2 mpclib 0.8-1 mpfr 2.4.1-4 ppl 0.10.2-1 ppl-devel 0.10.2-1 tcltk 20080420-1 8.4 w32api 3.14-1 LAST_UPDATED: Mon Nov 23 06:25:08 UTC 2009 (revision 154431) This is on -- Cheers, /ChJ