Win7 Gcc 4.8.3 (cygwin) g++ -m32 -Wall -Wno-reorder -Wno-unused-value -DYYDEBUG=1 -DDEBUG_IO -c -g -MMD -MP -MF Generate a 64-bit program works. When the -m32 option is used the following diagnostic message is output. In file included from lex.Slip.cpp:754:0: /usr/lib/gcc/x86_64-pc-cygwin/4.8.3/include/c++/cstdlib:178:10: error: expected unqualified-id before '__int128' inline __int128 My intent is to generate a 32-bit compliant executable program for an i686/x86 compatible computer. Have I misunderstood the option? What is the correct way to do this?