here is code:
while((nread = read(fd1,read_buf,sizeof(read_buf)))){ int ret = snprintf(write_buf,sizeof(write_buf),"%s",read_buf); int vprintf(const char *format, va_list ap); if(ret < 0){ │ int vfprintf(FILE *stream, const char *format, perror("snprintf failed"); │ va_list ap); }else{ │ int vsprintf(char *str, const char *format, va_list write(fd2,write_buf,strlen(write_buf)); │ ap); } │ int vsnprintf(char *str, size_t size, const char printf("strlen:%d, nread:%d\n",strlen(write_buf),nread); │ *format, va_list ap); bzero(write_buf,sizeof(write_buf)); │ Feature Test Macro Requirements for glibc (see fea‐ bzero(read_buf,sizeof(read_buf)); │ ture_test_macros(7)):} If i dont use -O2,the second cycle strlen is 11,nread is 10; but if i use gcc -O2 ,strlen is 10,nread is 10. I dont konw why , please give me an answer. thank you!