id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
5289	Library that uses Boost Filesystem would not start when the stdandard C++ library does not support the current locale	artyomtnk@…	Beman Dawes	"The standard C++ library required to support only C and POSIX locales, for others it may not be possible to create locale object.

Thus std::locale("""") would fail if the default system locale is not C or POSIX on may systems.

For example, GCC support locales only on Linux so basically global_locale() would
throw anywhere except Linux, in the Boost.Filesystem's code this means that it would
not be possible to even start program under Solaris or FreeBSD.

Even under Linux it is not possible to get to main() when linked with boost.filesystem shared library and the locale (LANG env. variable) is not supported.

Simple test. Link the program with boost.filesystem and try to run the program giving LANG=foo_BAR.UTF-8 - the program would not even start. Of course if may happen even for legal
locales like de_AU.UTF-8 that are not configured on this operating system.

I had attached the patch with following changes:

If std::locale("""") fails, check if current system locale's charset is UTF-8, if so install
utf-8 facet otherwise fallback to global locale.

It would cover most of frequent cases when the standard library does not support the global locale
and would not fail on locale generation, it may fail later on conversion if the charset is not supported. But it at least would work for ASCII subset.


The second change in the attached patch is that it always tries to use std::locale(""""), for example
MSVC fully supports them so why would not use the default one.

This is better then implement codecvt over Wide/Narrow API as it would not work correctly
on boundaries of double width encoding like Shift-JIS or BIG5.

For example of you have sequence ""XYYZ"" where X, YY and X are ""characters"" where YY is double
width encoded character then if you would do partial conversion of ""XY"" it would return ""error"", rather
then ""partial"" which is wrong.

So I think it is always best idea to give a best shot do standard C++ library rather then
install your own facets.

The patch is attached.

Artyom Beilis (Author of Boost.Locale)
"	Bugs	closed	Boost 1.47.0	filesystem	Boost 1.46.0	Showstopper	fixed