| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <27e6f108b713bb175dd2e77156ef61d0@kernel.crashing.org> Date: Thu, 4 Jan 2007 17:43:36 +0100 From: Segher Boessenkool <segher@...nel.crashing.org> To: "Albert Cahalan" <acahalan@...il.com> Cc: akpm@...l.org, linux-kernel@...r.kernel.org, s0348365@....ed.ac.uk, bunk@...sta.de, mikpe@...uu.se, torvalds@...l.org Subject: Re: kernel + gcc 4.1 = several problems > Adjusting gcc flags to eliminate optimizations is another way to go. > Adding -fwrapv would be an excellent start. Lack of this flag breaks > most code which checks for integer wrap-around. Lack of the flag does not break any valid C code, only code making unwarranted assumptions (i.e., buggy code). > The compiler "knows" > that signed integers don't ever wrap, and thus eliminates any code > which checks for values going negative after a wrap-around. You cannot assume it eliminates such code; the compiler is free to do whatever it wants in such a case. You should typically write such a computation using unsigned types, FWIW. Anyway, with 4.1 you shouldn't see frequent problems due to "not using -fwrapv while my code is broken WRT signed overflow" yet; and if/when problems start to happen, to "correct" action to take is not to add the compiler flag, but to fix the code. Segher - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists