错误：IntelliSense：标识符“strlen”在C中未定义

Question

我得到这个错误两次，我不知道为什么因为我在开头包含了stdlib.h所以我不确定我做错了什么或忘了添加？ 任何人都可以看到它为什么会出现？ 错误：IntelliSense：标识符“strlen”在C中未定义

#include <stdlib.h>
#include <stdio.h>
#include <time.h>

FILE*fp; 

char *symbols = "#~!$%^&*()+=<>?/@"; //Random Symbol is generated form this list

int main(void) {

char password[4 + 4 + 2 + 2 + 1];
int i, j=0, len=sizeof(password)-1;
int menuNum = 0;
int passwordCheck[15+1];



fp = fopen("passwords.txt", "a+"); 
//Opens the text file to save the Passwords

srand(time(NULL));
printf("       Main Menu\n");
printf("********************************\n");
printf("\nEnter 1 to Generate a New Password: ");
printf("\n\n");
printf("Enter 2 to Check Old Passwords: ");
printf("\n\n");
printf("Enter 3 to Exit. ");
printf("\n\n");
scanf("%d", &menuNum); // reads number

if (menuNum == 1)
{
    printf("********************************\n");
    printf("\nYour New Password is: \n\n");

//Each Password will Have 12 Characters(4 Uppercase letters, 4 Lowercase letters, 2 Numbers & 2 Symbols)

for (i = 0; i < 4; ++i)
    password[j++] = 'a' + rand() % ('z' - 'a' + 1); //Generates 4 random Lowercase characters 

for (i = 0; i < 4; ++i)
    password[j++] = 'A' + rand() % ('Z' - 'A' + 1); //Generates 4 random Uppercase characters

for (i = 0; i < 2; ++i)
    password[j++] = '0' + rand() % ('0' - '9' + 1); //Generates 2 random numbers

for (i = 0; i < 2; ++i)
    password[j++] = symbols[rand() % strlen(symbols)]; //Generates 2 random symbols

password[j] = '\0';
for(i = 0; i < sizeof(password)-1; ++i)
    {
    char c = password[i];
    j = rand() % len;
    password[i] = password[j];
    password[j] = c;
    }

printf("%s\n\n", password);
printf("********************************\n");
fprintf(fp, "\n%s", password); //Outputs the Generated Passoword to the text file
fclose(fp); //Closes the text file
system("pause");
}
else if (menuNum == 2)
{           
    printf("\nEnter your password for checking: ");
    scanf("%s", passwordCheck);  // reads password
    if (strlen(passwordCheck) > 15) // Checks length of Password
    {
        printf("'%s' is too long. Needs to be less then 15 Characters\n", passwordCheck);
        system("pause");
    }
    else if (strlen(passwordCheck) < 9) //Checks length of Password
    {
        printf("'%s' is too short. Needs to be more then 9 Characters\n", passwordCheck);
        system("pause");
    }
}

}

Answer 1

你需要添加：

#include <string.h>

如果您想知道函数需要哪些内容，请阅读其手册页。

Answer 2

你需要在程序的顶部#include <string.h>或strings.h

这会导入strlen函数的原型