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Subject: Re: [boost] [serialization]cannot build with Oracle Solaris Studio
From: Sylvester-Bradley, Gareth (Gareth.Sylvester-Bradley_at_[hidden])
Date: 2015-10-27 14:36:44

Hi Robert,

> It's hard to convey how much time and frustration is consumed in the
> tracking down of this stuff. Making a Boost library that is widely used
> is much, much harder than most people think.

Delivering for multiple platform/compiler/library versions is hard, and Boost library authors don't get enough thanks for doing so; so thank you.

I'll try to help with rules of thumb for working with the sync and locale related functions though.

At 27 October 2015 17:43, Robert Ramey wrote:
> as far as I can tell, streambuf have (pub)sync() declared and defined in
> all of the libraries. So one would think that all he has to do is to
> apply the (pub)sync and (pub)imbue to the streambuf and be done with it
> it. Well, one would be wrong. Spelunking the library source code, it
> seems that at least in a) and c) the stream caches the locale as well as
> passing on to the the streambuf. This suggests that the locale should
> be changed at the stream level when the library implements it (contrary
> to the standard.) And in fact, if one fails to call sync() at the
> stream level in a) (at least on input) the program will crash in a
> particularly hard to detect manner.

Sync is a function that only applies to input streams, not output. (Flush is more-or-less the equivalent for output streams.)
If our library code is handed a stream to work with, not a streambuf, it makes sense for the library to call sync() rather than rdbuf()->pubsync() so the caller sees the stream state (badbit, etc.) updated as expected.

Locales affect formatted input functions, which is why the stream (in its ios_base) caches the locale.
But the streambuf needs it too for the codecvt facet.
Again, as you suggest, if our caller hands us a stream to work with, it makes sense to imbue the stream which (via its basic_ios) makes sure both ios_base and its streambuf have the same locale. I think the standard indicates this too.

Standard libraries from before templated iostreams are, one hopes, long out of scope, but Boost.Iostreams still has the necessary configuration macros if they're not.

That's based on my experience with similar suite of platforms/std-libs/docs as you're knocking into shape, and it may all have been obvious to you after all your research, sorry if so.

Best of luck making the test matrix green!


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