CS计算机代考程序代写 #include

#include
#include
#include

using namespace std;

int main() {
char str1[] = “Hello”;
// fix 2 (see strcat below) :
// char str1[20] = “Hello”;
char str2[] = “World”;
char str3[] = “”;
// fix 1 (see strcpy below) :
// char str3[20] = “”;
int len;
int resp;

// strcpy: copy str1 into str3
//
// Note: this does not work with VS2019, as strcat is deprecated.
// It works with g++ though.
//
// this appears to work, but is in fact implementing a buffer overflow,
// as the destination string size (0) cannot contain the source string (size 5),
// the writing operation overflows into another variable’s memory space.
// In this case, it will overwrite ontl the content of str2.
// A solution here is to make str3 at least the size of str1.
strcpy(str3, str1);
cout << "strcpy(str3, str1) : " << str3 << endl; // strcpy_s is more secure, as it would throw an exception on the buffer overflow // but it is not available in g++... //resp = strcpy_s(str3, sizeof(str3), str1); //cout << "strcpy_s(str3, sizeof(str3), str1) : " << str3 << endl; // strcat: concatenates str1 and str2 // // Note: this does not work with VS2019, as strcat is deprecated. // It works with g++ though. // // This should work, but the buffer overflow above (strcpy) has already written on top // of the value of str2. Moreover, even if it appears to work after we fix the // size of str3 above, it also implements a buffer overflow, writing a part of the // resulting concatenated string beyond the space allocated to str1. // A solution here would be to increase the size of memory allocated to str1. // c-style strings can be very tricky! strcat(str1, str2); cout << "strcat(str1, str2): " << str1 << endl; // strcpy_s is more secure, as it would throw an exception on the buffer overflow // but it is not available in g++... //resp = strcat_s(str1, sizeof(str1), str2); //cout << "strcat_s(str1, sizeof(str1), str2) : " << str1 << endl; // total lenghth of str1 after concatenation len = strlen(str1); // strlen counts characters until the end marker that was added by strcpy // at then end of the buffer overflowed operation. cout << "strlen(str1) : " << len << endl; return 0; }