switch語句中case語句中變量初始化問題！

#include<stdio.h>
int main()
{
 int i=1;
 switch(i)
 {
  case 1:
    int a=1;
    printf("%d/n",a);
  break;
  case 2:
    printf("不可能的結果");
  break;
  default:break;
 }
 return 0;
}

 

編譯出現[Error] D:/文件包/C-Free/Temp/未命名1.cpp:11: error: jump to case label

            [Error] D:/文件包/C-Free/Temp/未命名1.cpp:8: error:   crosses initialization of `int a'

解決方案1：

#include<stdio.h>
int main()
{
 int i=1;
 switch(i)
 {
  case 1:
  {
    int a=1;
    printf("%d/n",a);
  }
  break;
  case 2:
    printf("不可能的結果");
  break;
  default:break;
 }
 return 0;
}

方案2：

#include<stdio.h>
void f();
int main()
{
 int i=1;
 switch(i)
 {
  case 1:
  f();
  break;
  case 2:
  printf("不可能的結果");
  break;
  default:break;
 }
 return 0;
}
void f()
{
  int a=1;
  printf("%d/n",a);
}

 

 

原因： for
    int a = 1;
the compiler knows Arnald needs a integer a with 1 as its
initial value. And it also found it is possible that in default
region, the a can be used. Since the compiler cannot make sure
the a will be initialized correctly for every flag, then it just
issue an error(warning for some other compilers), and hope you
can handle it...

And if you remove the default part, the error will dispear,
since there is no initialization *skip* now...

Just put them in the case scope if you really want it...