Question

我是c语言的新手。所以，我从Brian Kernighan和Dennis Ritchie的书（The C programming language）中复制了代码。我正在复制pg32示例。当我收到此错误时：

pg32.c: In function ‘int main()’:
pg32.c:16:23: error: type mismatch with previous external decl of ‘char longest []’ [-fpermissive]
pg32.c:7:6: error: previous external decl of ‘char longest [1000]’ [-fpermissive]
pg32.c: In function ‘int getl()’:
pg32.c:33:20: error: type mismatch with previous external decl of ‘char line []’ [-fpermissive]
pg32.c:6:6: error: previous external decl of ‘char line [1000]’ [-fpermissive]
pg32.c: In function ‘void copy()’:
pg32.c:50:20: error: type mismatch with previous external decl of ‘char line []’ [-fpermissive]
pg32.c:6:6: error: previous external decl of ‘char line [1000]’ [-fpermissive]
pg32.c:50:31: error: type mismatch with previous external decl of ‘char longest []’ [-fpermissive]
pg32.c:7:6: error: previous external decl of ‘char longest [1000]’ [-fpermissive]

我重新输入代码4次，同样的错误。我不确定，但我认为这是遗留问题。

#include<stdio.h>

#define MAXLINE 1000

int max;
char line[MAXLINE];
char longest[MAXLINE];

int getl(void);
void copy(void);

int main()
{
  int len;
  extern  int max;
  extern char longest[];

  max =0;
  while((len =getl()) > 0)
    if(len > max){
      max = len;
    copy();
    }

  if(max > 0)
    printf("%s", longest);
  return 0;
}

int getl(void)
{
  int c, i;
  extern char line[];

  for(i =0; i < MAXLINE-1 &&
    (c=getchar()) != EOF && c != '\n'; ++i)
    line[i] =c;

  if(c=='\n'){
    line[i] = c;
    ++i;
  }
  line[i] ='\0';
  return i;
}

void copy(void)
{
  int i;
  extern char line[], longest[];

  i=0;
  while((longest[i] = line[i]) != '\0')
    ++i;
}

我感谢任何帮助。

Answer 1

您将“line”和“long”声明为文件顶部的全局变量作为固定长度数组。然后你将它们重新声明为extern（顺便说一下，不需要这样）作为不确定长度的数组。编译器不喜欢这样，因此有两种解决方案：

将每extern line[]更改为extern line[MAXLINES]，将每extern char longest[]更改为extern char longest[MAXLINES]
删除所有extern声明，只使用顶部的全局变量

C程序 - 错误：类型与先前的'char line []'[-fpermissive] \的外部decl不匹配

1 个答案: