It fails here: system("$link $linkflags test$o ${cc_exe_out}test$exe $libs >test.ldo $redir_err") and die "Linker failed (see test.ldo)";
Most likely one of the variables($link, $linkflags and so forth) isn't set up or is set up incorrectly by this step. Therefore, could you send me a dump of your Cofigure::Data formed by the sizes step. You could get the dump if you added this line: die Configure::Data->dump(); before cc_gen('config/auto/sizes/test_c.in'); cc_build(); my %results=eval cc_run(); in config/auto/sizes.pl Sorry. I don't have cygwin and can't track down the problem personally.