c++ - 在 GDB 中打印 int **x

Question

我有一个指向数组的指针数组(称为板)。我想以正常方式打印它(这在 GDB 中很难)。

int col = 64, row = 2;
int **board = new int*[col];
for(int i = 0; i < col; i++)
    board[i] = new int[row];

我尝试了以下命令:

p *array@len (the problem is it prints in hexadecimal values not as integer)

x/100w array (It scrolls so much down that i cannot even see the values)

*(T (*)[N])p (where p is array, T is type of array and N is size of it) [It just does not print accurate]

Answer 1

I want to print it in normal way

最好的办法是编写一个 print_board 例程，然后您可以从 GDB 调用它。

(which is pretty hard in GDB).

那是因为你让它变得困难了。

问题是你的板子，而不是在内存中是连续的(按照惯例，在 GDB 中打印是微不足道的)，而是分散在 64 个独立的 block 中，每个 block 有 2 个值。

由于您使用的是 C++，因此最好使用 vector 的 vector :

vector<vector<int>> board;
board.resize(col);
for (int i = 0; i < col; i++) {
  board[i].resize(row);
}

(gdb) print board
$1 = std::vector of length 64, capacity 64 =
 {std::vector of length 2, capacity 2 = {0, 0},
  std::vector of length 2, capacity 2 = {0, 0},
  ...

附言提问时，显示实际 代码会有所帮助。您的问题的 board 类型错误，并且将 board 与 array 混合在一起。

更新:

How can I do that (use print_board from GDB)?

这是一个例子。假设您的源代码如下所示:

 1  #include <stdio.h>
 2  
 3  int main()
 4  {
 5    int col = 16, row = 2;
 6    int **board = new int*[col];
 7  
 8    for (int i = 0; i < col; i++) {
 9      board[i] = new int[row];
10    }
11  
12    // Initialize elements to something interesting, so we can see them
13    // printed.
14    for (int i = 0; i < col; i++)
15      for (int j = 0; j < row; j++)
16        board[i][j] = 100*i + j;
17  
18    return 0;
19  }
20  
21  void print_board(int **board, int col, int row)
22  {
23    for (int j = 0; j < row; j++) {
24      for (int i = 0; i < col; i++) {
25        printf("\t%d", board[i][j]);
26      }
27      printf("\n");
28    }
29  }

然后，使用 GDB:

gdb -q ./a.out
(gdb) break 18
(gdb) run

Breakpoint 2, main () at t.cc:18
18    return 0;

(gdb) call print_board(board, col, row)
    0   100 200 300 400 500 600 700 800 900 1000    1100    1200    1300    1400    1500
    1   101 201 301 401 501 601 701 801 901 1001    1101    1201    1301    1401    1501

瞧