How to use strerror_l with current locale?

Question

I'm fixing some Linux code which used strerror (not thread-safe) for multi-threading. I found that strerror_r and strerror_l are both thread-safe. Due to different definitions for strerror_r (depending on _GNU_SOURCE it is differently defined) I'd like to use the newer strerror_l function, but how am I supposed to obtain a locale_t object for the current locale? I'm not using iconv or anything, just plain libc, and I don't see how I can obtain a "default locale" object (I don't care in what language the error is printed, I just want a human readable string.)

score 3 · Accepted Answer · edited Jun 29 '19 at 03:12

3

If you pass "" to the locale parameter newlocale will allocate a locale object set to the current native locale[1]

[1]http://pubs.opengroup.org/onlinepubs/9699919799/functions/newlocale.html

static  locale_t locale;

bool MyStrerrorInit(void)
{
    locale = newlocale(LC_CTYPE_MASK|LC_NUMERIC_MASK|LC_TIME_MASK|LC_COLLATE_MASK|
                       LC_MONETARY_MASK|LC_MESSAGES_MASK,"",(locale_t)0);

    if (locale == (locale_t)0) {
       return false;
    }

    return true;
}

char * MyStrerror(int error)
{
    return strerror_l(error, locale);
}

edited Jun 29 '19 at 03:12

Will

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answered Jan 15 '15 at 15:29

clockley1

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1

You can use LC_ALL_MASK instead of ORing all of the category masks – osvein May 07 '20 at 00:14

Daniel Le · Answer 2 · 2021-09-18T23:15:19.863

3

You could use POSIX uselocale:

strerror_l(errno, uselocale((locate_t)0));

edited Sep 18 '21 at 23:15

answered Sep 18 '21 at 13:47

Daniel Le

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Well, technically, `NULL` is odd here. It's not `NULL`, it's `(locale_t)0`. `uselocale((locale_t)0)`. Is `locale_t` guaranteed to be a pointer? – KamilCuk Sep 18 '21 at 13:57
1

@KamilCuk You're right, I mixed `uselocale` up with `setlocale`. I don't think `locale_t` is guaranteed to be a pointer, except that it is in glibc. I've incorporated this into my answer. Thank you. – Daniel Le Sep 18 '21 at 23:16

How to use strerror_l with current locale?

2 Answers2