[英]memcpy creates segmentation fault
I have the following code, which takes an unsorted list of songs and artists and sorts and displays them. 我有以下代码,其中包含未排序的歌曲和艺术家列表,并对它们进行排序和显示。
int main()
{
SongList totalList; // has a public 2d array 'unsortedSongs' variable
char songs[100][80] =
{
{"David Bowie 'Ziggy Stardust'",},
{"Smokey Robinson 'You've Really Got A Hold On Me'",},
{"Carole King 'You've Got A Friend'",},
// many more songs here totaling to 100
{"Joni Mitchel 'A Case Of You'",},
{"Prince 'Kiss'"}
};
memcpy(&totalList.unsortedSongs, &songs, sizeof(songs)); // this causes a segmentation fault
totalList.displaySortedList();
return 0;
}
I took the code for memcpy almost directly off of the example here , so I am confused as to why this doesn't work. 我几乎直接从此处的示例中删除了memcpy的代码,因此对于为什么此方法不起作用感到困惑。 Can someone help me fix this? 有人可以帮我解决这个问题吗?
edit: 编辑:
this is the initialization of SongList 这是SongList的初始化
class SongList
{
public:
char unsortedSongs[100][80];
public:
void displaySortedList();
void sortList();
string rearrange(char[]);
string getSongsForArtist(int*);
};
This line: 这行:
memcpy(&totalList.unsortedSongs, &songs, sizeof(songs));
should be: 应该:
memcpy(totalList.unsortedSongs, songs, sizeof(songs));
since both songs
and totalList.unsortedSongs
will decay to pointers which is analogus to the first example in the reference you cited: 因为songs
和totalList.unsortedSongs
都将衰减为指针,这totalList.unsortedSongs
您引用的参考中的第一个示例:
memcpy ( person.name, myname, strlen(myname)+1 );
http://www.cplusplus.com/reference/cstring/memcpy/ http://www.cplusplus.com/reference/cstring/memcpy/
Memcpy expects the source and destination variables to be pointers ( void * ) Memcpy希望源变量和目标变量是指针(void *)
totalList.unsortedSongs is a pointer. totalList.unsortedSongs是一个指针。
When you write &totalList.unsortedSongs you are asking for the address of the pointer. 当您编写&totalList.unsortedSongs时,您正在询问指针的地址。 A bit like "the pointer to the pointer"... See here: http://www.cplusplus.com/doc/tutorial/pointers/ 有点像“指向指针的指针” ...参见此处: http : //www.cplusplus.com/doc/tutorial/pointers/
I just compiled your code and it works fine. 我只是编译了您的代码,所以效果很好。
However, I find your initializer list rather curious. 但是,我发现您的初始化器列表很奇怪。 While it works, it makes me think you actually want to define an array of an array of char[80], not just an array of char[80]. 虽然有效,但让我认为您实际上想定义char [80]数组的数组,而不仅仅是char [80]的数组。
So I think your display routine might be wrong and your debugger just not showing you the real line where things go wrong, because of optimization or whatnot. 因此,我认为您的显示例程可能是错误的,并且由于优化或其他原因,调试器只是没有向您显示出哪里出错了。
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