Iago Toral <ito...@igalia.com> writes: > On Wed, 2016-03-09 at 19:04 -0800, Francisco Jerez wrote: >> Matt Turner <matts...@gmail.com> writes: >> >> > On Wed, Mar 9, 2016 at 1:37 PM, Francisco Jerez <curroje...@riseup.net> >> > wrote: >> >> Iago Toral <ito...@igalia.com> writes: >> >> >> >>> On Tue, 2016-03-08 at 17:42 -0800, Francisco Jerez wrote: >> >>>> brw_cfg.h already has include guards, remove the "#pragma once" which >> >>>> is redundant and non-standard. >> >>> >> >>> FWIW, I think using both #pragma once and include guards is a way to >> >>> keep portability while still getting the performance advantage of >> >>> #pragma once where it is supported. >> >>> >> >> It's highly unlikely to make any significant difference on any >> >> reasonably modern compiler. I cannot measure any change in compilation >> >> time locally from my cleanup. >> >> >> >>> Also it seems that we do the same thing in many other files... >> >>> >> >> Really? I'm not aware of any other file where we use both. >> > >> > There are quite a few in glsl/ >> >> Heh, apparently you're right. Anyway it seems rather pointless to use >> '#pragma once' in a bunch of scattered header files with the expectation >> to gain some speed, the improvement from a single header file is so >> minuscule (if it will make any difference at all on a modern compiler >> and compilation workload, which I doubt) that we would have to use it >> universally in order to have the chance to measure any improvement. >> >> Can we please just decide for one of the include guard styles and use it >> consistently? Given that the majority of header files in the Mesa >> codebase use old-school define guards, that it's the only standard >> option, that it has well-defined semantics in presence of file copies >> and hardlinks, and that the performance argument against it is rather >> dubious (although I definitely find '#pragma once' prettier and more >> concise), I'd vote for using preprocessor define guards universally. >> >> What do other people think? > > I think we have to use define guards necessarily since #pragma once is > not standard even it it has wide support. So the question is whether we > want to use only define guards or define guards plus #pragma once. I am > fine with doing only define guards as you propose. >
*Shrug* I have the impression that the only real advantage of '#pragma once' is that you no longer need to do the ifndef/define dance, so I don't think I can see much benefit in doing both. > Iago
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