c - g_ptr_array_sort 不工作

Question

我是 GPtrArray 的新手，遇到了一些问题。我像下面这样写了我的代码。但是g_ptr_arrat_sort(a, compare_items);不管用..我试图通过 gdb 进行调试，但我发现我的程序有问题..gdb 说， (gdb) p *阿尔法 $1 = {item = 6295648, name = 0x601080 "o\024", price = 6295712, value = 3.1105108254111529e-317} (gdb) p *测试版$3 = {item = 6295680, name = 0x6010a0 "/\"", price = 6295744, value = 0}

这不是我输入 GPtrArray* a 的内容!!

我该如何解决这个问题？？

我的代码:

1 #include <stdio.h>
2 #include <glib.h>
3 
4 typedef struct _DATA {
5         int item;
6         char* name;
7         int price;
8         double value;
9 } DATA;
10 
11 int compare_items (gpointer, gpointer);
12 void printAll (gpointer, gpointer);
13 
14 DATA data [] = {{7143, "aaa", 1231234, 235.5},
15                 {5231, "bbb", 532458, 238.75},
16                 {8751, "ccc", 872654, 125.47},
17                 {2354, "ddd", 87542, 564.4}};
18 
19 int main(void)
20 {
21     GPtrArray* a = g_ptr_array_new ();
22     g_ptr_array_add (a, &data[0]);
23     g_ptr_array_add (a, &data[1]);
24     g_ptr_array_add (a, &data[2]);
25     g_ptr_array_add (a, &data[3]);
26 
27     g_ptr_array_sort (a, (GCompareFunc) compare_items);
28 
29     g_ptr_array_foreach (a, printAll, (gpointer) NULL);
30 
31     return 0;
32 }
33 
34 gint compare_items (gpointer a, gpointer b) {
35 
36         DATA* alpha = (DATA *) a;
37         DATA* beta = (DATA *) b;
38 
39         return (gint) (alpha->item - beta->item);
40 }
41 
42 void printAll (gpointer a, gpointer b) {
43         DATA* alpha = (DATA*) a;
44         printf ("item : %d, name : %s, price : %d, value : %lf\n", alpha ->  item, alpha -> name, alpha -> price, alpha -> value);
45         return;
46 }

输出:

item : 7143, name : aaa, price : 1231234, value : 235.500000
item : 5231, name : bbb, price : 532458, value : 238.750000  
item : 8751, name : ccc, price : 872654, value : 125.470000
item : 2354, name : ddd, price : 87542, value : 564.400000

Answer 1

根据 documentation ,

The comparison function for g_ptr_array_sort() doesn't take the pointers from the array as arguments, it takes pointers to the pointers in the array.

这意味着您的比较函数可能应该如下所示:

gint compare_items (gpointer a, gpointer b) {
  DATA* alpha = *(DATA **) a;
  DATA* beta = *(DATA **) b;
  return (gint) (alpha->item - beta->item);
}