这是我的代码（带有调试打印）：

char *full_file_name = malloc(sizeof(char));
FILE *ob_file;

/*creating full file name*/
strcpy(full_file_name, file_name);
strcat(full_file_name, ".ob");
printf("\n full_file_name :%s", full_file_name);

/* -- Creating the new file and inputting data --*/
ob_file = fopen(full_file_name, "w");
printf("\n full_file_name :%s", full_file_name);

这是打印结果：

为什么会这样？该怎么办呢？