foo.c: In function 'main':
foo.c:25:6: error: 'i' undeclared (first use in this function)
   25 |  for(i=1;i<=n;i++)
      |      ^
foo.c:25:6: note: each undeclared identifier is reported only once for each function it appears in
foo.c:27:7: error: 'j' undeclared (first use in this function)
   27 |   for(j=1;j<=n;j++)
      |       ^
foo.c:63:23: warning: format '%d' expects argument of type 'int', but argument 2 has type 'int *' [-Wformat=]
   63 |  printf("边长为：%d",&side_lenth);
      |                      ~^  ~~~~~~~~~~~
      |                       |  |
      |                       |  int *
      |                       int
      |                      %ls
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    6 |  scanf("%d",&n);
      |  ^~~~~~~~~~~~~~
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    7 |  scanf("%d",&m);
      |  ^~~~~~~~~~~~~~

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