c - 如何使用 strncat 而不担心缓冲区溢出问题？

Question

我有一个缓冲区，我正在做很多 strncat。我想确保我永远不会溢出缓冲区大小。

char buff[64];

strcpy(buff, "String 1");

strncat(buff, "String 2", sizeof(buff));

strncat(buff, "String 3", sizeof(buff));

我想说的不是sizeof(buff)，而是buff——xxx。我想确保我永远不会覆盖缓冲区

Answer 1

考虑现有字符串的大小和空终止符

#define BUFFER_SIZE 64
char buff[BUFFER_SIZE];

//Use strncpy
strncpy(buff, "String 1", BUFFER_SIZE - 1);
buff[BUFFER_SIZE - 1] = '\0';

strncat(buff, "String 2", BUFFER_SIZE - strlen(buff) - 1);

strncat(buff, "String 3", BUFFER_SIZE - strlen(buff) - 1);