Dne 28.11.2014 v 19:50 Joe Perches napsal(a): > On Fri, 2014-11-28 at 14:33 +0100, Michal Marek wrote: >> On 2014-11-21 05:22, Peter Teoh wrote: >>> This warning was found in v3.18-rc3-68-g20f3963 of Linus git-tree. >>> >>> SHIPPED scripts/kconfig/zconf.hash.c >>> HOSTCC scripts/kconfig/zconf.tab.o >>> In file included from scripts/kconfig/zconf.tab.c:2537:0: >>> scripts/kconfig/menu.c: In function ‘get_symbol_str’: >>> scripts/kconfig/menu.c:590:18: warning: ‘jump’ may be used >>> uninitialized in this function [-Wmaybe-uninitialized] >>> jump->offset = strlen(r->s); >>> ^ >>> scripts/kconfig/menu.c:551:19: note: ‘jump’ was declared here >>> struct jump_key *jump; >>> ^ >> >> First of all, the warning is bogus (the condition under which 'jump' is >> used is stronger than that under which 'jump' is initialized). But since >> people have been reporting the warning on and off for some time, we have >> to shut it up somehow, as the affected gcc versions are not dying out, >> apparently. >> >> >>> - if (head && location && menu == location) >>> + if (head && location && (menu == location) && >>> (jump)) >>> jump->offset = strlen(r->s); >> >> Let's assume, for the sake of argument, that gcc is right and jump may >> be uninitialized here. Then the added check for jump being non-null just >> tests an uninitialized variable and thus behaves randomly. It prevents >> the code from writing to NULL->offset, but does not prevent it from >> writing to <random address>->offset. > > Maybe the 'right' thing to do is to mark the xmalloc > prototype as "__attribute__((returns_nonnull))"
The warning says that 'jump' can be used uninitialized (random), not that it can be NULL. Michal -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
