c-大小为8的读取无效.正在尝试制作2D阵列

Question

试图制作一个2D阵列，但我从valgrind 中得到了这个错误

==226== HEAP SUMMARY:
==226==     in use at exit: 0 bytes in 0 blocks
==226==   total heap usage: 38 allocs, 38 frees, 9,793 bytes allocated
==226== 
==226== All heap blocks were freed -- no leaks are possible
==226== 
==226== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)
==226== 
==226== 1 errors in context 1 of 2:
==226== Invalid read of size 8
==226==    at 0x108BB7: freeBoard (Battleships.c:55)
==226==    by 0x108B81: createBoard (Battleships.c:47)
==226==    by 0x108AD6: main (Battleships.c:30)
==226==  Address 0x522ff60 is 0 bytes after a block of size 32 alloc'd
==226==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==226==    by 0x108B29: createBoard (Battleships.c:40)
==226==    by 0x108AD6: main (Battleships.c:30)
==226== 
==226== 
==226== 1 errors in context 2 of 2:
==226== Invalid write of size 8
==226==    at 0x108B5D: createBoard (Battleships.c:44)
==226==    by 0x108AD6: main (Battleships.c:30)
==226==  Address 0x522ff60 is 0 bytes after a block of size 32 alloc'd
==226==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==226==    by 0x108B29: createBoard (Battleships.c:40)
==226==    by 0x108AD6: main (Battleships.c:30)
==226== 
==226== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)

这是分配/释放的代码

void createBoard(int* widthPtr, int* heightPtr)                                             /* Creates the 2D Board Array. */
{
char** board;
int i;
board = (char**)malloc((*heightPtr) * sizeof(char*));
for (i = 0; i < *widthPtr; i++)
{
board[i] = (char*)malloc((*widthPtr) * sizeof(char));
}
freeBoard(board, widthPtr);
}
void freeBoard(char** board, int* widthPtr)
{
int i;
for (i = 0; i < *widthPtr; i++)
{
free(board[i]);
}
free(board);
}

我正在尝试制作一个指定宽度/高度的2D数组，这些数组是整数。在数组的每个部分中都将存储一个字符。

任何帮助都将是伟大的，谢谢。

Answer 1

for (i = 0; i < *widthPtr; i++)
{
board[i] = (char*)malloc((*widthPtr) * sizeof(char));
}

应该是

for (i = 0; i < *heightPtr; i++)
{
board[i] = (char*)malloc((*widthPtr) * sizeof(char));
}

否则，您将迭代NCOLUMNS次(您希望通过NROWS维度进行迭代(

与freeBoard()相同

此外，请注意，在这行

board[i] = (char*)malloc((*widthPtr) * sizeof(char));

你更喜欢

board[i] = malloc(*widthPtr);

因为：

1( 没有必要铸造malloc和朋友

2(sizeof(char)保证为1