Malloc 向系统申请分配指定size个字节的内存空间。返回类型是 void* 类型。void* 表示未确定类型的指针。C,C++规定，void* 类型可以强制转换为任何其它类型的指针。-Malloc to the system for the allocation of the specified size bytes of memory space. Return type is void*. void* indicates undetermined type pointer. C, C++ regulations, void* type can be cast to any other type of pointer.