转：C语言:error: a label can only be part of a statement and a declaration is not a statement|

转： C语言:error: a label can only be part of a statement and a declaration is not a statement|

原文：https://blog.csdn.net/qq_30242609/article/details/52858115 

场景还原

一个简单的switch语句Demo

#include<stdio.h>
int main()
{
  int a=1, b=2, re;
  char c;
  scanf("%c", &c);
  switch(c)
  {
    case '+':
      re = a + b;
      break;
    case '$':
      re = a - b;
      re++;
      break;
    case '#':
      int other = 3;
      re = a + b + other;
      break;
    default:
      printf("Illegal input!
");
      break;
  }
  printf("%d
", re);
}

出错原因

在switch语句里定义了新的变量。在上例中在case '#'语句块中定义了新的变量other。
解决办法

给定义了新变量的case语句块套上大括号，这个错误就没了。
改后代码

#include<stdio.h>
int main()
{
  int a=1, b=2, re;
  char c;
  scanf("%c", &c);
  switch(c)
  {
    case '+':
      re = a + b;
      break;
    case '$':
      re = a - b;
      re++;
      break;
    case '#':
    {
      int other = 3;
      re = a + b + other;
      break;
    }
    default:
      printf("Illegal input!
");
      break;
  }
  printf("%d
", re);
}