\u5bf9\u4e8estrcpy\uff0csprintf\uff0cstrcat\u8fd9\u4e9b\u4e0d\u5b89\u5168\u7684\u51fd\u6570\u7684\u8ba8\u8bba\u5e94\u8be5\u7b97\u662f\u4e0d\u5c11\u4e86\uff0c\u5927\u5bb6\u90fd\u77e5\u9053\u53ef\u4ee5\u7528strncpy\uff0csnprintf\u548cstrncat\u6765\u66ff\u6362\u5b83\u4eec\u3002\u4f46\u5b9e\u9645\u5de5\u4f5c\u4e2d\u4f3c\u4e4e\u8fd9\u4e9b\u201c\u5b89\u5168\u7248\u201d\u7684\u51fd\u6570\u5e26\u6765\u7684\u7591\u60d1\u8fd8\u662f\u4e0d\u5c0f\uff0c\u603b\u7ed3\u4e86\u4e00\u4e0b\uff0c\u5217\u5728\u8fd9\u91cc\u3002<\/p>\n
1.sprintf(char * str, const char * format, …) -> snprintf(char * str, size_t size, const char * format, …)<\/p>\n
vsprintf(char * str, const char * format, va_list ap) -> vsnprintf(char * str, size_t size, const char * format, va_list ap)<\/p>\n
\u6309\u7167C\/C++\u6807\u51c6\uff0csnprintf\u548cvsnprintf\u6c38\u8fdc\u4e0d\u4f1a\u5f80str\u4e2d\u8f93\u51fa\u591a\u4e8esize\u6240\u6307\u5b9a\u7684\u5b57\u8282\u6570\u7684\u5b57\u7b26\uff08\u5305\u62ec\u7ed3\u5c3e\u7684’\/0’\uff09\uff0c\u5b83\u4eec\u4e5f\u4fdd\u8bc1\u4e86\u4e00\u5b9a\u4f1a\u5728str\u4e2d\u5199\u5165’\/0’\uff0c\u6240\u4ee5\u5728\u4f7f\u7528\u8fd9\u4e2a\u51fd\u6570\u540e\u4e0d\u7528\u62c5\u5fc3\u7ed3\u5c3e\u7684\u95ee\u9898\u3002<\/p>\n
\u4e3e\u4f8b:<\/p>\n
\u7136\u800c\uff0cVC\u4e2d\u7684_snprintf\u51fd\u6570\u5e76\u6ca1\u6709\u6309\u7167\u8fd9\u6837\u7684\u89c4\u5b9a\u6765\u505a\uff0c\u5b83\u5728\u8f93\u51fa\u7f13\u51b2\u533a\u4e0d\u591f\u5927\u65f6\u5c31\u4e0d\u4f1a\u8f93\u51fa\u7ed3\u5c3e\u7684’\/0′(\u8ddfstrncpy\u7684\u884c\u4e3a\u7c7b\u4f3c)\u3002\u6240\u4ee5\u8981\u8ba9\u4e0a\u9762\u7684\u7a0b\u5e8f\u5de5\u4f5c\u6b63\u5e38\uff0c\u5fc5\u987b\u505a\u76f8\u5e94\u7684\u4fee\u6539\u3002<\/p>\n \u5982\u679c\u8981\u4fdd\u8bc1\u53ef\u79fb\u690d\u6027\uff0c\u5c31\u5f97\u6309VC\u7684\u5199\u6cd5\uff0c\u505a\u4e00\u6b21\u5bf9\u4e8e\u6807\u51c6\u6765\u8bf4\u5f88\u591a\u4f59\u7684\u201c\u586b0\u201d\u7684\u64cd\u4f5c\uff0c\u518d\u901a\u8fc7\u5b9a\u4e49\u5b8f\u6765\u533a\u522b\u5e73\u53f0\u5206\u522b\u9009\u7528snprintf\u6216_snprintf\u3002<\/p>\n 2. strcat(char * dest, const char * src) -> strncat(char * dest, const char * src, size_t n);<\/p>\n \u8fd9\u4e2a\u51fd\u6570\u6bd4\u8f83\u7b80\u5355\uff0c\u5b83\u4fdd\u8bc1\u4e0d\u4f1a\u5199\u5165\u591a\u4e8en+1\u4e2a\u5b57\u7b26\uff0c\u5e76\u4e14\u4fdd\u8bc1\u6700\u540e\u4e00\u5b9a\u4ee5’\/0’\u7ed3\u675f\u3002<\/p>\n \u4e3e\u4f8b\uff1a<\/p>\n 3. strcpy(char * dest, const char * src) -> strncpy(char * dest, const char * src, size_t n);<\/p>\n strncpy\u662f\u4e00\u4e2a\u6bd4\u8f83\u5bb9\u6613\u51fa\u9519\u7684\u51fd\u6570\uff0c\u5b83\u4fdd\u8bc1\u590d\u5236src\u4e2d\u4e0d\u591a\u4e8en\u5b57\u8282\u7684\u5185\u5bb9\uff0c\u4f46\u662f\u5982\u679csrc\u7684\u524dn\u4e2a\u5b57\u8282\u4e2d\u6ca1\u6709\u5305\u542b’\/0’\uff0c\u5c31\u4f1a\u5bfc\u81f4 dest\u6ca1\u6709\u6b63\u5e38\u7684\u4ee5’\/0’\u7ec8\u6b62\u3002\u53e6\u5916\uff0c\u5b83\u8fd8\u4fdd\u8bc1\u5982\u679csrc\u7684\u957f\u5ea6\u5c0f\u4e8en\uff0c\u5219dest\u5269\u4f59\u7684\u90e8\u5206\u90fd\u4f1a\u4ee5’\/0’\u586b\u5145\u3002\u5728\u7528\u8fd9\u4e2a\u51fd\u6570\u65f6\uff0c\u6709\u4e00\u4e2a\u6700\u4f73\u5b9e\u8df5\u5c31 \u662f\u5148\u628adest\u4ee50\u586b\u5145\uff0c\u5e76\u4f20\u5165dest\u7684\u957f\u5ea6\u51cf1\u7684\u503c\u4f5c\u4e3an\uff0c\u8fd9\u6837\u53ef\u4ee5\u786e\u4fdd\u5b89\u5168\u3002<\/p>\n \u4e3e\u4f8b\uff1a<\/p>\n \u5bf9\u4e8estrcpy\uff0csprintf\uff0cstrcat\u8fd9\u4e9b\u4e0d\u5b89\u5168\u7684\u51fd\u6570\u7684\u8ba8\u8bba\u5e94\u8be5\u7b97\u662f\u4e0d\u5c11 … \u7ee7\u7eed\u9605\u8bfb char buf[5];
\nsnprintf(buf, 5, \"This is a test string.\"); \/\/ buf becomes \"This\", buf[4] is '\/0'
\nsnprintf(buf, 6, \"This is a test string.\"); \/\/ ERROR: buffer overflow
\nsnprintf(buf, 5, \"abc\"); \/\/ buf becomes \"abc\", the value of buf[3] is '\/0', buf[4] is undefined.<\/code><\/p>\nchar buf[5];
\n_snprintf(buf, 5, \"This is a test string.\");\/\/ buf becomes \"This \", buf[4] is ' '
\nbuf[4] = 0; \/\/ buf[4] is '\/0' now.
\n_snprintf(buf, 6, \"This is a test string.\"); \/\/ ERROR: buffer overflow
\n_snprintf(buf, 5, \"abc\"); \/\/ buf becomes \"abc\", the value of buf[3] is '\/0', buf[4] is undefined.<\/code><\/p>\nchar dest[5] = \"abc\";
\nstrncat(dest, \"defghijklmn\", 5 - 3 - 1); \/\/ dest becomes \"abcd\", dest[4] is '\/0',
\n \/\/ always minus the buffer length by 1 as the value of n.
\nstrncat(dest, \"defghijklmn\", 5 - 3); \/\/ ERROR: buffer overflow<\/code><\/p>\n\u3000\u3000char buf[5] = {0}; \/\/ Always zero-fill the buffer,
\n \/\/ always use this form to initialize the stack arrays to get
\n \/\/better performance over memset.
\nchar * buf2 = new char[5];
\nmemset(buf2, 0, 5); \/\/ Always zero-fill the buffer
\nstrncpy(buf, \"abcde\", 5); \/\/ ERROR: buf is not null-terminated.
\nstrncpy(buf2, \"abcde\", 5 - 1); \/\/ Right, always minus the buffer length by 1
\n \/\/as the value of n. buf becomes \"abcd\", buf[4]
\n \/\/is '\/0' by initilization;
\n \/\/ This is a common error in the existing code.
\nchar buf3[5];
\nconst char * str = \"Test\";
\nstrncpy(buf3, str, strlen(str)); \/\/ Wrong, buf may not null-terminated,
\n \/\/ potential buffer-overflow
\nstrncpy(buf3, str, strlen(str)+1); \/\/ Wrong, potential buffer-overflow.
\n \/\/No difference with using strcpy.
\n<\/code><\/p>\n","protected":false},"excerpt":{"rendered":"