c++ - 这是允许的 : memcpy(dest, src, 0)

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Answer 1

正如人们可能对一个理智的界面所期望的那样，零是一个有效的大小，并且不会导致任何事情发生。 C99 7.21.1/2 中各种字符串处理函数(包括 memcpy)的规范特别允许:

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. [...] 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.