问我找不到分段错误的原因

EN

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>

char** parse_cmdline(const char *cmdline){

    char** input;
    int counter = 0;
    char* token;
    token = strtok(cmdline);
    
    int tokenlen = strlen(token);
    
    input = realloc(input , sizeof(char*)+tokenlen*sizeof(char));
    input[counter] = token;
        
    while( token != NULL ) {
            token = strtok(NULL, " ");
            printf("%s\n",token);
            tokenlen = strlen(token);
            input = realloc(input , sizeof(char*)+tokenlen*sizeof(char));
            counter++;
            input[counter] = token;
    }
    return input;
}

int main(){

    char* cmdline = NULL;
    size_t cmdlength = 0 ;
    char** arguments;

    int status;
    pid_t pid;
    while (1){
    
        getline(&cmdline , &cmdlength , stdin);
        arguments = parse_cmdline(cmdline);

        pid = fork();
        if(pid == 0){
        
            if(access(arguments[0], F_OK) == 0 ) {
            
                    if(access(arguments[0], X_OK)){
                    
                        execv(arguments[0],arguments);
                        exit(0);
                        
                    } else {
                    
                        printf("%s: Permission denied",arguments[0]);
                        exit(-1);
                    
                    }
                    
            } else {
            
                printf("%s: No such file or directory",arguments[0]);
                exit(-1);
            
            }
            
        } else {
        
            waitpid(-1, &status, 0);
            
        }
            
        free(arguments);
        cmdline = NULL ;
        cmdlength = 0 ;
    }   
    return 0;
}