fork download
copy 
  1. #include <stddef.h>
  2. #include <iostream>
  3. using namespace std;
  4.  
  5. // https://w...content-available-to-author-only...t.org/confluence/display/seccode/EXP08-C.+Ensure+pointer+arithmetic+is+used+correctly
  6.  
  7. struct big {
  8. 	unsigned long long ul1_1; // 8
  9. 	unsigned long long ul1_2; // 8
  10. 	unsigned long long ul1_3; // 8
  11. 	int si_4; // 4
  12. 	int si_5; // 4
  13. };
  14.  
  15. void getAdrs(void *p) {
  16. 	cout << p << endl;
  17. }
  18.  
  19. int main() {
  20. 	size_t skip = offsetof(struct big, ul1_2);
  21.  
  22. 	struct big *s = (struct big *)malloc(sizeof(struct big));
  23.  
  24. 	cout << skip << endl; // 8
  25.  
  26. 	getAdrs(s               ); // 0x9a38008 
  27. 	getAdrs(s + skip        ); // 0x9a38108 (+256)
  28. //	getAdrs((char *)s + skip); // 0x9a38010 (+2)
  29. 	getAdrs((char *)s + skip); // 0x9a38010 (+8 NOT +2) // modified 
  30.  
  31. 	unsigned long long val[4];
  32. 	getAdrs(&val[0]); // 0xbfacc0f0
  33. 	getAdrs(&val[1]); // 0xbfacc0f8 (+8)
  34. 	getAdrs(&val[2]); // 0xbfacc100 (+16)
  35.  
  36. 	free(s);
  37. 	s = NULL;
  38.  
  39. 	return 0;
  40. }
Success #stdin #stdout 0s 3428KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
8
0x968a008
0x968a108
0x968a010
0xbfe55320
0xbfe55328
0xbfe55330
https://ideone.com/b5kmS4
EXP08-C. Ensure pointer arithmetic is used correctly
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!