It's legal C99. See DR258 / C99+TC3. But be careful, reading trap representations is UB. http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_283.htm http://www.

It's legal C99. See DR258 / C99+TC3. But be careful, reading trap representations is UB. http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_283.htm http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_283.htm http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf