std::locale breakage on MacOS 10.6 with LANG=en_US.UTF-8

Question

I have a C++ application that I am porting to MacOSX (specifically, 10.6). The app makes heavy use of the C++ standard library and boost. I recently observed some breakage i

Answer 1

I have encountered this problem very recently on Ubuntu 14.04 LTS and on a Raspberry Pi running the latest Raspbian Wheezy.

It has nothing to do with OS X, rather with a combination of G++ and Boost (at least up to V1.55) and the default locale settings on certain platforms. There are Boost bug tickets sort of related to this issue, see ticket #4688 and ticket #5928.

My "solution" was first to do some extra locale setup, as suggested by this AskUbuntu posting:

sudo locale-gen en_US en_US.UTF-8
sudo dpkg-reconfigure locales

But then, I also had to make sure that the environment variable LC_ALL is set to the value of LANG (it is advisable to put this in your .profile):

export LC_ALL=$LANG

In my case I use the locale en_US.UTF-8.

Final remark: the OP said "This program fails when I run this through g++". I understand that this thread was started in 2009, but today there is absolutely no need to use GCC or G++ on the Mac, the much better LLVM/Clang compiler suite is available from Apple free of charge, see the XCode home page.

Answer 2

I had the same problem, checked LANG and LC_MESSAGES and they are not set when you lunch the application through Finder, so the following lines saved the day:

unset("LANG");
unset("LC_MESSAGES");

Answer 3

Ok I don't have an answer for you, but I have some clues:

• This isn't limited to OS X 10.6. I get the same result on a 10.4 machine.
• I looked at the GCC source for libstdc++ and hunted around for _S_create_c_locale. What I found is on line 143 of config/locale/generic/c_locale.cc. The comment there says "Currently, the generic model only supports the "C" locale." That's not promising. In fact if I do LANG=C the runtime error goes away, but any other value for LANG I try causes the same error, regardless of what arguments I give to the locale constructor. (I tried locale::classic(), "C", "", and the default). This is true as far back as GCC 4.0
• That same page has a reference to libstdc++ mailing list discussion on this topic. I don't know how fruitful it is: I only followed it a little way down, and it gets very technical very fast.

None of this tells you why the default locale on 10.6 wouldn't work with std::locale but it does suggest a workaround, which is to set LANG=C before running the program.

Answer 4

The situation is still the same. But some functionality may be gained by

setlocale( LC_ALL, "" );

This gets you UTF-8 coding on wide iostreams but not money formatting, for my two data points.

locale::global( locale( "" ) );

should be equivalent, but it crashes if subsequently run in the very same program.

Answer 5

The _S_create_c_locale exception seems to indicate some sort of misconfiguration: check that whatever your LC_ALL or LANG environment variable is set to, exists in the output of locale -a.

$ env LC_ALL=xx_YY ./test
terminate called after throwing an instance of 'std::runtime_error'
  what():  locale::facet::_S_create_c_locale name not valid
Aborted
$ env LC_ALL=C ./test
$ echo $?
0

But since you're on OS X, I'm not really sure how locale information is supposed to be handled.