On 19 August 2016 at 09:07, Jeffrey Walton wrote: >> You've basically gone chasing after some unrelated definition (that of >> uint64_t) which has nothing to do with _rdrand64(), looking at >> unrelated implementation details of that different type, and the >> simple solution is to just use the type in the function declaration. > > That's how Intel documents it. They document it as unsigned __int64 but that's not a standard type. That's not a standard type. You found some definition of __int64 in a different set of GCC headers and chased that, but there's no guarantee that the header you looked in defined it consistently with how it's used in the Intel docs. > A long time ago I was told to use Intel's documentation because GCC > does not provide it (cf., > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=68081). GCC might not document the function, but the header unambiguously defines the function signature, and it takes unsigned long long*.
