Kimmo Fredriksson wrote: > Are there any predefined macros that could be used to detect the > endiannes at compile time, that I could use in conditional > compilation? No, not by default. If your project uses autoconf you can use macro AC_C_BIGENDIAN to create a define in the generated config.h; see the manual and the 'autobook': http://www.gnu.org/manual/autoconf/autoconf.html http://sources.redhat.com/autobook/ If you're compiling for a large set of platforms you should really consider autoconf etc.; if you're only compiling for a small set you can test for platform specific defines (e.g. _WIN32 and _M_IX86 or __sun__) and then make your own defines and #error if nothing matches. Rup.