请问编译器正常,平台显示 "编译错误"怎么回事?

/tmp/compiler_lira2tui/src: In function ‘int add(char, char, char*)’: /tmp/compiler_lira2tui/src:7:9: 错误：‘strrev’ was not declared in this scope; did you mean ‘strsep’? 7 | strrev(s1); | ^~ | strsep

代码如下：

#include<iostream>
#include<cstring>
using namespace std;
#define maxn 10050
int add(char* s1, char* s2, char* buf){
    if (strlen(s1) > strlen(s2)) return add(s2,s1,buf);
    strrev(s1);
    strrev(s2);
    char* p=s1;
    char* q=s2;
    char* r=buf;
    int cx = 0;

    while(*p){
        int t = (*p -'0') + (*q-'0') +cx;
        *r = t % 10 +'0';
        cx = t / 10;
        p++; q++; r++;
    }
    while(*q){
        int t = *q-'0' + cx;
        *r = t % 10 +'0';
        cx = t / 10;
        q++; r++;
    }
    if(cx==1) {
    *r = '1';
    r++;
    }
    *r='\0';
    strrev(buf);
    return 0;
}

int main(){
    char  a[maxn],b[maxn],c[maxn];
    memset(a,0,maxn);   memset(b,0,maxn);   memset(c,0,maxn);
    int n;
    cin>>n;
    a[0]='2' ;
    b[0]='1';
    for(int i=3; i<=n ; i++ ){
    strcpy(c,a);
    add(b,c,a);
    strcpy(b,c);
    }
    cout<<a<<endl;
    return 0;
}