snprintf 是 C/C++ 程序中最常见的函数了，但是snprintf 在Windows和 Linux上的行为并不一致，对于跨平台的开发，有时会带来严重的缓冲区溢出问题。
本文提供了一个安全检查的版本，保证了 Windows和 Linux上的行为的一致性，任何情况下不会溢出。
建议用户使用 snprintf_chkd_exit 版本，任何错误导致退出程序 ! 这样避免对 snprintf_chkd 的返回值进行检查，保证了逻辑清晰和程序健壮。
/** * snprintf_chkd() * A checked version of snprintf() for both GCC and MSVC * * see: * <stdarg.h> * https://linux.die.net/man/3/snprintf * * The functions snprintf() and vsnprintf() do not write more than size bytes * (including the terminating null byte (' ')). * If the output was truncated due to this limit then the return value is the * number of characters (excluding the terminating null byte) which would have * been written to the final string if enough space had been available. * Thus, a return value of size or more means that the output was truncated. */static int snprintf_chkd (char *outputbuf, size_t bufsize, const char *format, ...){ int len; va_list args; va_start(args, format); len = vsnprintf(outputbuf, bufsize, format, args); va_end(args); if (len < 0) { len = 0; *outputbuf = ' '; } else if (len >= (int) bufsize) { /* output was truncated due to bufsize limit */ len = (int) bufsize - 1; /* for MSVC */ outputbuf[len] = ' '; } return len;}/** * snprintf_chkd_exit() * A crashed on error version of snprintf. * * If exitcode not given (= 0), same as snprintf_safe() */static int snprintf_chkd_exit (int exitcode, char *outputbuf, size_t bufsize, const char *format, ...){ int len; va_list args; va_start(args, format); len = vsnprintf(outputbuf, bufsize, format, args); va_end(args); if (len < 0) { len = 0; *outputbuf = ' '; /* exit on error if exitcode given (not 0) */ if (exitcode) { fprintf(stderr, "(%s:%d) fatal: output error is encountered.n", __FILE__, __LINE__); exit(exitcode); } } else if (len >= (int) bufsize) { /* output was truncated due to bufsize limit */ len = (int) bufsize - 1; /* for MSVC */ outputbuf[len] = ' '; /* exit on error if exitcode given (not 0) */ if (exitcode) { fprintf(stderr, "(%s:%d) fatal: output was truncated. (%s...)n", __FILE__, __LINE__, outputbuf); exit(exitcode); } } return len;}