On 19/01/2017 09:03, leon zadorin wrote: > Last time I checked in C, as well as in C++, standards -- shifting by > the number of bits greater *or equal* to the size of the type is > undefined behavior... > > e.g. something like "An expression is shifted by a negative number or > by an amount greater than or equal to the width of the promoted > expression (6.5.7)." from > https://www.securecoding.cert.org/confluence/display/c/CC.+Undefined+Behavior#CC.UndefinedBehavior-ub_51 > > The exact place in C++14 and or latest C standards escape me right > now, but the thesis of this UB stands correct I think... In C11, it's 6.5.7p3 http://port70.net/~nsz/c/c11/n1570.html#6.5.7p3 > The integer promotions are performed on each of the operands. The > type of the result is that of the promoted left operand. If the value > of the right operand is negative or is greater than or equal to the > width of the promoted left operand, the behavior is undefined. C11: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf C99: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf http://port70.net/~nsz/c/c11/ http://port70.net/~nsz/c/c99/ > what is sizeof(long) on your target? Sane 64-bit platforms define sizeof(long) to 8 Win64 defines sizeof(long) to 4 /troll I think most (if not all) gcc ports define CHAR_BIT to 8. Regards.
