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authorPablo Neira Ayuso <pablo@netfilter.org>2012-07-30 03:08:51 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2012-07-30 03:36:52 +0200
commit2165f38d2582e88e8a9dd9416f34eca7a7672e5a (patch)
treee58c6519f8e825a9feb2367660126bdff6dbfeb1 /include/linux/kernel.h
parentf1c668268e9ddaedd8d78d7ae44cd26db1e8469f (diff)
iptables-restore: fix parameter parsing (shows up with gcc-4.7)
This patch fixes parameter parsing in iptables-restore since time ago. The problem has shown up with gcc-4.7. This version of gcc seem to perform more agressive memory management than previous. Peter Lekensteyn provided the following sample code similar to the one in iptables-restore: int i = 0; for (;;) { char x[5]; x[i] = '0' + i; if (++i == 4) { x[i] = '\0'; /* terminate string with null byte */ printf("%s\n", x); break; } } Many may expect 0123 as output. But GCC 4.7 does not do that when compiling with optimization enabled (-O1 and higher). It instead puts random data in the first bytes of the character array, which becomes: | 0 | 1 | 2 | 3 | 4 | | RANDOM | '3' | '\0' | Since the array is declared inside the scope of loop's body, you can think of it as of a new array being allocated in the automatic storage area for each loop iteration. The correct code should be: char x[5]; for (;;) { x[i] = '0' + i; if (++i == 4) { x[i] = '\0'; /* terminate string with null byte */ printf("%s\n", x); break; } } Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'include/linux/kernel.h')
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