[C compilation] collection of error reporting problems

1、[Note] each undeclared identifier is reported only once for each function it appears in

[注] Each undeclared identifier is reported only once for each function that appears to be（Wrong or overwritten identifier）

如：

printf("f("%s", "%s") = %d\n", p, q, result);

修改：

printf("f(\"%s\", \"%s\") = %d\n", p, q, result);

printf 函数里面 double quotes required \ output without error.

2、[Warning] initialization discards ‘const’ qualifier from pointer target type

[警告] Discarded at initialization Discarded from pointer target typeconst限定符

如：

const int a[10] = {
    0};
char* p = a;			//会出现此Warning

解决办法：

const int a[10] = {
    0};
const int* p = a;

3、[Error] variable-sized object may not be initialized

[错误] Variable-length objects are not initialized

如：

int n = 5;
int a[n] = {
    1,2,3,4,5};

错因：
for variable length arrays(The length is controlled by a variable), Cannot initialize at the same time as the array is defined,A separate assignment initialization is required after the definition.

修改：

int n = 5;
int a[n];
memset(a, 0, sizeof(a));		//合法初始化,将a的所有元素初始化为0

4、[Error] ld returned 1 exit status

[错误] ldReturns an exit status
可能原因：

• The result of the last run was not closed

5、[Error] stray ‘\241’ in program

可能原因：There are illegal characters in the program,Might have accidentally converted to full-width input.

6、The debugging results are inconsistent with the running results

如：

#include <stdio.h>
#include <string.h>

#define LEN 500 //限制输入的字符串长度

int main(){
    
    
    char str[LEN+1], differ[LEN+1];    //Here the array is not initialized
    int len_str, len_differ;
    int i;
    
    scanf("%s", str);
    len_str = strlen(str);
    
    strncpy(differ, str, 1);
    len_differ = strlen(differ);
    //在differsearch one by onestr中的元素
    for(i=0; i<len_str; i++){
    
        //没被记录
        if( strchr(differ, str[i]) == NULL ){
    
            //A single character is spliced ​​todiffer末尾 
            differ[strlen(differ)] = str[i];
            differ[strlen(differ) + 1] = '\0';
        }
    }
    printf("%d", strlen(differ));
    
    
    return 0;
}

错误原因：暂且未知
解决办法：把数组初始化

7、Cannot enter while debugging

问题描述：
A dialog box pops up after clicking debug,But the dialog is minimized immediately,且无法输入.

原因：
断点设置在 scanf 那一行.

解决办法：
修改断点,Set a breakpoint after the input function.

8、[Error] assignment to expression with array type

错误原因：

• 数组不能直接给数组赋值.

解决办法：

• 若是字符串,可使用strcpy函数
• 若是数组,You need to assign values ​​one by one.