[PATCH/RFC 07/17] gettext.c: work around us not using setlocale(LC_CTYPE, "")

Change the gettext setup code to arrange for messages to be emitted in the user's requested encoding, but avoid setting LC_CTYPE from the environment for the whole program.

In 107880a I removed our use of setlocale(LC_CTYPE, "") because of a bug in the GNU C Library [1]. Even if it wasn't for that bug we wouldn't want to use LC_CTYPE at this point, because it'd require auditing all the code that uses C functions whose semantics are modified by LC_CTYPE.

But only setting LC_MESSAGES as we do creates a problem, since we declare the encoding of our PO files[2] the gettext implementation will try to recode it to the user's locale, but without LC_CTYPE it'll emit something like this on 'git init'

    Bj? til t?ma Git lind ? /hl/agh/.git/

Gettext knows about the encoding of our PO file, but we haven't told it about the user's encoding, so all the non-US-ASCII characters get encoded to question marks.

But we're in luck! We can set LC_CTYPE from the environment only while we call nl_langinfo and bind_textdomain_codeset. That suffices to tell gettext what encoding it should emit in, so it'll now say:

    Bjó til tóma Git lind í /hl/agh/.git/

And the equivalent ISO-8859-1 string will be emitted under a ISO-8859-1 locale.

With this change way we get the advantages of setting LC_CTYPE (talk to the user in his language/encoding), without the drawbacks (changed semantics for C functions we rely on).

In the long term we should probably see about getting that bug in glibc fixed, and audit our code so it won't fall apart under a non-C locale.

1. http://sourceware.org/bugzilla/show_bug.cgi?id=6530
2. E.g. "Content-Type: text/plain; charset=UTF-8\n" in po/is.po

Suggested-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
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 gettext.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)