On Fri, Feb 21, 2014 at 3:48 PM, Kenneth Graunke <kenn...@whitecape.org> wrote: > On 02/21/2014 02:43 PM, Matt Turner wrote: >> On Fri, Feb 21, 2014 at 2:25 PM, Kenneth Graunke <kenn...@whitecape.org> >> wrote: >>> Generally, I only use PACKED when something -relies- on a particular >>> memory layout. Is it really worth second guessing the compiler here? >>> Presumably it had a reason for choosing a larger size other than sheer >>> stupidity... >> >> We're not second guessing the compiler. >> >> The C99 spec says the type of an enum is implementation defined. >> Adding __attribute__((__packed__)) to an enum has the same behavior as >> gcc's -fshort-enum flag, but the flag would obviously cover all enums. >> The gcc non-bugs page [0] says that they don't want to make >> -fshort-enums the default because of [ABI] incompatibilities with >> other compilers. They suggest setting a field width of the enum in a >> struct, but in general that seems prone to errors (e.g., adding a >> 256th value to an enum, but having specified an 8-bit field width on >> the enum field) that using packed wouldn't have. Since we aren't >> likely to hit that, would you rather me just set a field width? >> >> [0] http://gcc.gnu.org/onlinedocs/gcc/Non-bugs.html#index-fshort-enums-3868 > > Okay, that's bordering more on 'stupidity' than I thought. These enums > are only ever used internally, so ABI compatibility is completely > irrelevant. And they do get copied around a fair bit. > > __attribute__((packed)) seems nicer than making every user of the value > specify a field width. > > It would be nice to add your explanation here to the commit message.
Sure, will do. _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
