foo.c:8:13: error: unknown type name 'BigInt'; did you mean 'int'?
 void Output(BigInt *p);
             ^~~~~~
             int
foo.c:9:10: error: unknown type name 'BigInt'; did you mean 'int'?
 void mul(BigInt *p, int x);
          ^~~~~~
          int
foo.c:10:10: error: unknown type name 'BigInt'; did you mean 'int'?
 void Mul(BigInt *p1,BigInt *p2,BigInt *p3);
          ^~~~~~
          int
foo.c:10:21: error: unknown type name 'BigInt'; did you mean 'int'?
 void Mul(BigInt *p1,BigInt *p2,BigInt *p3);
                     ^~~~~~
                     int
foo.c:10:32: error: unknown type name 'BigInt'; did you mean 'int'?
 void Mul(BigInt *p1,BigInt *p2,BigInt *p3);
                                ^~~~~~
                                int
foo.c: In function 'main':
foo.c:18:2: error: unknown type name 'BigInt'; use 'struct' keyword to refer to the type
  BigInt x1;
  ^~~~~~
  struct 
foo.c:19:4: error: request for member 'n' in something not a structure or union
  x1.n=1; x1.digit[0]=1;   // 初始化为1
    ^
foo.c:19:12: error: request for member 'digit' in something not a structure or union
  x1.n=1; x1.digit[0]=1;   // 初始化为1
            ^
foo.c:20:23: warning: implicit declaration of function 'mul' [-Wimplicit-function-declaration]
  for(i=1; i<=n1; i++) mul(&x1,a1); //做第一个乘方 
                       ^~~
foo.c:22:2: error: unknown type name 'BigInt'; use 'struct' keyword to refer to the type
  BigInt x2;
  ^~~~~~
  struct 
foo.c:23:4: error: request for member 'n' in something not a structure or union
  x2.n=1; x2.digit[0]=1;   // 初始化为1
    ^
foo.c:23:12: error: request for member 'digit' in something not a structure or union
  x2.n=1; x2.digit[0]=1;   // 初始化为1
            ^
foo.c:26:2: error: unknown type name 'BigInt'; use 'struct' keyword to refer to the type
  BigInt x3;
  ^~~~~~
  struct 
foo.c:27:2: warning: implicit declaration of function 'Mul' [-Wimplicit-function-declaration]
  Mul(&x1,&x2,&x3);
  ^~~
foo.c:28:2: warning: implicit declaration of function 'Output' [-Wimplicit-function-declaration]
  Output(&x3);
  ^~~~~~
foo.c: At top level:
foo.c:32:10: error: unknown type name 'BigInt'; did you mean 'int'?
 void Mul(BigInt *p1,BigInt *p2,BigInt *p3)
          ^~~~~~
          int
foo.c:32:21: error: unknown type name 'BigInt'; did you mean 'int'?
 void Mul(BigInt *p1,BigInt *p2,BigInt *p3)
                     ^~~~~~
                     int
foo.c:32:32: error: unknown type name 'BigInt'; did you mean 'int'?
 void Mul(BigInt *p1,BigInt *p2,BigInt *p3)
                                ^~~~~~
                                int
foo.c:45:10: error: unknown type name 'BigInt'; did you mean 'int'?
 void mul(BigInt *p, int x)
          ^~~~~~
          int
foo.c:61:13: error: unknown type name 'BigInt'; did you mean 'int'?
 void Output(BigInt *p)
             ^~~~~~
             int
foo.c: In function 'main':
foo.c:16:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d",&a1,&n1);
  ^~~~~~~~~~~~~~~~~~~~~~
foo.c:17:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d",&a2,&n2);
  ^~~~~~~~~~~~~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务