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gettext.c: remove/reword a mostly-useless comment

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Mostly remove the comment I added 5e9637c629 (i18n: add
infrastructure for translating Git with gettext, 2011-11-18). Since
then we had a fix in 9c0495d23e (gettext.c: detect the vsnprintf bug
at runtime, 2013-12-01) so we're not running with the "set back to C
locale" hack on any modern system.

So having more than 1/4 of the file taken up by a digression about a
glibc bug that mostly doesn't happen to anyone anymore is just a
needless distraction. Shorten the comment to make a brief mention of
the bug, and where to find more info by looking at the git history for
this now-removed comment.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Ævar Arnfjörð Bjarmason 2021-01-11 14:14:51 +01:00 committed by Junio C Hamano
parent 450d740847
commit 9371c0e9dd
1 changed files with 15 additions and 79 deletions
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gettext.c
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@ -87,88 +87,24 @@ static int test_vsnprintf(const char *fmt, ...)
static void init_gettext_charset(const char *domain)
{
/*
This trick arranges for messages to be emitted in the user's
requested encoding, but avoids setting LC_CTYPE from the
environment for the whole program.
This primarily done to avoid a bug in vsnprintf in the GNU C
Library [1]. which triggered a "your vsnprintf is broken" error
on Git's own repository when inspecting v0.99.6~1 under a UTF-8
locale.
That commit contains a ISO-8859-1 encoded author name, which
the locale aware vsnprintf(3) won't interpolate in the format
argument, due to mismatch between the data encoding and the
locale.
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'
under the Icelandic locale:
Bj? til t?ma Git lind ? /hlagh/.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 /hlagh/.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 major
drawbacks (changed semantics for C functions we rely on).
However foreign functions using other message catalogs that
aren't using our neat trick will still have a problem, e.g. if
we have to call perror(3):
#include <stdio.h>
#include <locale.h>
#include <errno.h>
int main(void)
{
setlocale(LC_MESSAGES, "");
setlocale(LC_CTYPE, "C");
errno = ENODEV;
perror("test");
return 0;
}
Running that will give you a message with question marks:
$ LANGUAGE= LANG=de_DE.utf8 ./test
test: Kein passendes Ger?t gefunden
The vsnprintf bug has been fixed since glibc 2.17.
Then we could simply set LC_CTYPE from the environment, which would
make things like the external perror(3) messages work.
See t/t0203-gettext-setlocale-sanity.sh's "gettext.c" tests for
regression tests.
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
*/
setlocale(LC_CTYPE, "");
charset = locale_charset();
bind_textdomain_codeset(domain, charset);
/* the string is taken from v0.99.6~1 */
/*
* Work around an old bug fixed in glibc 2.17 (released on
* 2012-12-24), at the cost of potentially making translated
* messages from external functions like perror() emitted in
* the wrong encoding.
*
* The bug affected e.g. git.git's own 7eb93c89651 ([PATCH]
* Simplify git script, 2005-09-07), which is the origin of
* the "David_K\345gedal" test string.
*
* See a much longer comment added to this file in 5e9637c6297
* (i18n: add infrastructure for translating Git with gettext,
* 2011-11-18) for more details.
*/
if (test_vsnprintf("%.*s", 13, "David_K\345gedal") < 0)
setlocale(LC_CTYPE, "C");
}