> On Thu, Apr 18, 2013 at 06:58:42AM +0000, YAMAMOTO Takashi wrote: >> > On Tue, Apr 16, 2013 at 11:34:52PM +0000, YAMAMOTO Takashi wrote: >> >> > On Tue, Apr 16, 2013 at 11:39:50PM +0900, Takehiko NOZAKI wrote: >> >> >> so that the struct _locale __C_locale in libc is much more wasteful. >> >> > >> >> > I should add that it is an internal detail and the way the composed C >> >> > locale is stored can and likely will change later. So the way it is >> >> > essentially a copy of (old) global locale is just a way to be minimally >> >> > intrusive. >> >> > >> >> > Joerg >> >> >> >> i care the API. >> >> >> >> if you really want it be in libc, how about having libc provide a >> >> "locale_t get_static_c_locale();" style API rather than using NULL? >> >> it's better because 1) less code in *_l, 2) autoconf-like can detect >> >> the extension easily, and 3) a portable application can trivially >> >> have a fallback implementation using newlocale+pthread_once. >> > >> > It adds more cost on the caller side. So far, there are three mechanisms >> > available (especially for libraries): >> > >> > (1) Adhoc access to internal locale state. This is used with glibc. >> > (2) Explicit newlocale(). >> > (3) Implicit access via 0 argument to *_l. >> > >> > The first one is clearly a hack and not acceptable. Portable code can >> > always conditionally use (2), but it requires additional setup and >> > storage cost. (3) is used by Apple (which is where a large part of the >> > *_l interface originates from) and FreeBSD. It is orthogonal to (2) and >> > certainly easier to use. Exposing it via a special library call is also >> > possible and effectively a way to implement (2) by a static wrapper. >> > It still adds more cost to every caller and this is a classic case where >> > there are typically much more callers. >> > >> > Joerg >> >> (3) adds small costs to every calls of *_l, even when the extension >> is not used. i sounds worse than a one-time cost of (2) to me. > > (2) still needs to load the address (instead of a constant), so it isn't > free either. Given that this is very popular as functionality and at > least on modern CPUs often implementable as conditional-move, it sounds > like a much better trade off.
very popular? i'm not aware of a single software which uses this extension. can you provide examples? YAMAMOTO Takashi > > Joerg