Re: [boost] [filesystem][cygwin] Standard conformance for wide characters

Subject: Re: [boost] [filesystem][cygwin] Standard conformance for wide characters
From: Beman Dawes (bdawes_at_[hidden])
Date: 2009-01-14 08:56:32

On Tue, Jan 13, 2009 at 1:17 PM, Emil Dotchevski
<emildotchevski_at_[hidden]> wrote:
> On Tue, Jan 13, 2009 at 6:16 AM, Beman Dawes <bdawes_at_[hidden]> wrote:
>> I've decided not to attempt support for Cygwin in the next version of
>> Boost.Filesystem.
>
> I pulled the plug on Cygwin support at my company a couple of years
> ago for the lack of wchar_t support. They ought to support it.

Since in this case Cygwin is just a packager of other people's work,
it isn't on their radar screen.

I doubt it would take much work to add gcc wide character support; the
compiler already supports wchar_t as does the C++ standard library.
IIUC, the only piece of the puzzle that is missing is the C language
library support. I suspect any of us could code that up in short
order, but I don't want to take the time to figure out how to
integrate it into their build system and sheppard the changes through
their process.

>> Cygwin's lack of library support for wchar_t is the problem . For the
>> current Boost.Filesystem version (v2), the necessary workarounds are so
>> pervasive that the implementation code is much harder to read and maintain.
>
> Is it true that had the interface of boost::filesystem been defined in
> terms of utf8, then the only platform on which wchar_t support would
> have been instrumental is Windows, and we wouldn't have had problems
> with Cygwin?

The problem isn't so much the interface as the internals. Windows'
native character type for file names is wchar_t.

>> IIUC, the reason Cygwin doesn't provide C++ standard library support for
>> wchar_t is that the underlying C library is missing the C wchar_t functions.
>> Perhaps Boosters who care about Cygwin could spearhead an effort to add the
>> missing C support?
>
> You're right that it's missing the needed C library functions, but I
> was able to hack into the C++ headers to trick them to support
> std::wstring anyway. That's not the same as full wchar_t support, but
> it was the only thing I personally cared about.
>
> My hack broke with one of the Cygwin releases that followed and I gave
> up on tracking down why, but I suppose if someone cares enough about
> this it can be done (my approach was to inject a modified version of
> one of the gcc-specific header files into the compiler include path,
> I'm not sure if this would be good enough for Boost.)

I suspect it is far easier to just fix the problem at the Cygwin
source code level that trying to hack and maintain patches for Cygwin
object code distributions.

--Beman