Here's the documentation for -fwrapv in gcc-4.0 in
http://gcc.gnu.org/onlinedocs/gcc-4.0.0/gcc/Code-Gen-Options.html#Code- Gen-Options
-fwrapv This option instructs the compiler to assume that signed arithmetic overflow of addition, subtraction and multiplication wraps around using twos-complement representation. This flag enables some optimizations and disables other. This option is enabled by default for the Java front-end, as required by the Java language specification.
Since we assume this of all processors, we need to enable this flag.
Brad