c++ - 是否保证按字节的零 int 是零的表示？

Question

特别是，以下断言保证成立:

int i;
memset(&i, 0, sizeof(int));
assert(i == 0);

Answer 1

C++ 中的

int 可以有 ones' complement , two's complement ，或signed magnitude二进制表示法 [basic.fundamental]/7 :

Types bool, char, char16_­t, char32_­t, wchar_­t, and the signed and unsigned integer types are collectively called integral types. A synonym for integral type is integer type. The representations of integral types shall define values by use of a pure binary numeration system. [ Example: This International Standard permits two's complement, ones' complement and signed magnitude representations for integral types.  — end example ]

在每种表示形式中，对于该整数类型来说，全零位的值为零，因此可以保证断言始终为真。