Created
March 28, 2012 12:02
-
-
Save HappyCerberus/2225673 to your computer and use it in GitHub Desktop.
Prevod jednorozmerne - dvourozmerne pole
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
/* Copyright (c) 2012 Mgr. Simon Toth (kontakt@simontoth.cz) | |
* Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php | |
*/ | |
#include <stdio.h> | |
#include <string.h> | |
union multipole | |
{ | |
int pole1[35]; | |
int pole2[7][5]; | |
}; | |
int main() | |
{ | |
union multipole x; | |
memset(&x,0,sizeof(x)); // vynulovani | |
x.pole1[10] = 10; | |
// nasledujici pristup je podle C99 nedefinovane chovani | |
// novy standard C1X pravidlo upresnuje tak, ze nasledujici | |
// radek je validni. Vetsina kompilatoru by mela projit bez problemu. | |
printf("%d\n",x.pole2[2][0]); | |
/* Pro upresneni v C99 je pristup k polozce unionu, jine nez je ta | |
* ktera byla naposled zapsana definovan jako UB (undefined behaviour). | |
* C1X to upresnuje tak, ze takovy pristup je UB pouze tehdy, pokud se | |
* pristupuje k bytum, ktere nebyly pri posledni zapisu pouzity. | |
* | |
* Jinak receno, pokud sizeof(zapsana_polozka) >= sizeof(ctena_polozka) neni to UB. | |
*/ | |
return 0; | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment