The first sizeof(dhm_g) should have been sizeof(dhm_p). So, do you attribute this to a simple typo (hard to catch at a glance due to similar letter shapes), "single letter variable names are bad" but the wikipedia page on DH also calls them p and g - it takes a little digging to get that "root" and "modulus" would have been better names, but maybe having them directly match the most common form of the equation would have made them easier to review...
Or do you just add it to the list of C crimes, that "passing storage length and pointer" is maybe the worst possible way to return written-to storage from a function :-)
Or do you just add it to the list of C crimes, that "passing storage length and pointer" is maybe the worst possible way to return written-to storage from a function :-)