c++ - 我可以调用 memcpy() 和 memmove() 并将 "number of bytes"设置为零吗？

Question

当我实际上没有东西可以移动/复制时，我是否需要处理将 memmove()/memcpy() 作为边缘情况的情况

int numberOfBytes = ...
if( numberOfBytes != 0 ) {
    memmove( dest, source, numberOfBytes );
}

或者我应该直接调用函数而不检查

int numberOfBytes = ...
memmove( dest, source, numberOfBytes );

是否需要检查前一个片段？

Answer 1

来自 C99 标准 (7.21.1/2):

Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on a call to that function. Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still have valid values, as described in 7.1.4. On such a call, a function that locates a character finds no occurrence, a function that compares two character sequences returns zero, and a function that copies characters copies zero characters.

所以答案是否定的；检查是没有必要的(或者是的；你可以通过零)。