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
| ||
|
Date: Tue, 17 May 2011 20:22:27 +0100 From: Ben Hutchings <bhutchings@...arflare.com> To: Michał Mirosław <mirqus@...il.com> Cc: Jeff Garzik <jgarzik@...ox.com>, David Miller <davem@...emloft.net>, netdev@...r.kernel.org Subject: Re: sfc: an enumeration is not a bitmask On Tue, 2011-05-17 at 21:09 +0200, Michał Mirosław wrote: > 2011/5/17 Jeff Garzik <jgarzik@...ox.com>: > > 2011/5/17 David Miller <davem@...emloft.net>: > >> An enumeration is not a bitmask, instead it means one out of the set > >> of enumerated values will be used. > > > > It's a decade-old kernel practice to use 'enum' to define typed > > constants, preferred over macros that convey no type information and > > disappear after cpp phase. > > > > So your assertion about enumerations is demonstrably not true, as it > > is often used in the kernel. Call it enum abuse if you want, but it > > is consistent with code all over the kernel. > > > > That said, I agree that warnings should of course be addressed in some manner. > > Old age of the mistake doesn't make it correct. > > Disappearance of the #defines can be resolved by using enum of bit > positions (and maybe field lengths) and #define of (1 << bit_position) > if it is useful for something to remain after preprocessing. The point is that there is no specific type information for macros, whether they are simple literal numbers or left-shift expressions. The type of an enumerator in C is actually that of the underlying integer type, not the enumeration type as in C++. However, a compiler or static analysis tool (such as sparse) may keep track of both the language-specified type and some other associated type of an expression in order to diagnose possible type errors. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists