`_configthreadlocale`

Article
12/02/2022

Configures per-thread locale options.

Syntax

int _configthreadlocale( int per_thread_locale_type );

Parameters

per_thread_locale_type
The option to set. One of the options listed in the following table.

Return value

The previous per-thread locale status (_DISABLE_PER_THREAD_LOCALE or _ENABLE_PER_THREAD_LOCALE), or -1 on failure.

Remarks

The _configthreadlocale function is used to control the use of thread-specific locales. Use one of these per_thread_locale_type options to specify or determine the per-thread locale status:

Option	Description
`_ENABLE_PER_THREAD_LOCALE`	Make the current thread use a thread-specific locale. Subsequent calls to `setlocale` in this thread affect only the thread's own locale.
`_DISABLE_PER_THREAD_LOCALE`	Make the current thread use the global locale. Subsequent calls to `setlocale` in this thread affect other threads using the global locale.
0	Retrieves the current setting for this particular thread.

These functions affect the behavior of setlocale, _tsetlocale, _wsetlocale, and _setmbcp. When per-thread locale is disabled, any subsequent call to setlocale or _wsetlocale changes the locale of all threads that use the global locale. When per-thread locale is enabled, setlocale or _wsetlocale only affects the current thread's locale.

If you use _configthreadlocale to enable a per-thread locale, set the preferred locale in that thread immediately afterward by a call to setlocale or _wsetlocale.

If per_thread_locale_type isn't one of the values listed in the table, this function invokes the invalid parameter handler, as described in Parameter validation. If execution is allowed to continue, this function sets errno to EINVAL and returns -1.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Routine	Required header
`_configthreadlocale`	`<locale.h>`

Example

// crt_configthreadlocale.cpp
//
// This program demonstrates the use of _configthreadlocale when
// using two independent threads.
//
// Compile by using: cl /EHsc /W4 crt_configthreadlocale.cpp

#include <locale.h>
#include <mbctype.h>
#include <process.h>
#include <windows.h>
#include <stdio.h>
#include <time.h>

#define BUFF_SIZE 100

// Retrieve the date and time in the current
// locale's format.
int get_time(unsigned char* str)
{
    __time64_t  ltime;
    struct tm   thetime;

    // Retieve the time
    _time64(&ltime);
    _gmtime64_s(&thetime, &ltime);

    // Format the current time structure into a string
    // using %#x is the long date representation,
    // appropriate to the current locale
    if (!strftime((char *)str, BUFF_SIZE, "%#x",
                  (const struct tm*)&thetime))
    {
        printf("strftime failed!\n");
        return -1;
    }
    return 0;
}

// This thread sets its locale to German
// and prints the time.
unsigned __stdcall SecondThreadFunc( void* /*pArguments*/ )
{
    unsigned char str[BUFF_SIZE];

    _configthreadlocale(_ENABLE_PER_THREAD_LOCALE);

    // Set the thread code page
    _setmbcp(_MB_CP_ANSI);

    // Set the thread locale
    printf("The thread locale is now set to %s.\n",
           setlocale(LC_ALL, "German"));

    // Retrieve the time string from the helper function
    if (get_time(str) == 0)
    {
        printf("The time in German locale is: '%s'\n", str);
    }

    _endthreadex( 0 );
    return 0;
}

// The main thread spawns a second thread (above) and then
// sets the locale to English and prints the time.
int main()
{
    HANDLE          hThread;
    unsigned        threadID;
    unsigned char   str[BUFF_SIZE];

    // Enable per-thread locale causes all subsequent locale
    // setting changes in this thread to only affect this thread.
    _configthreadlocale(_ENABLE_PER_THREAD_LOCALE);

    // Retrieve the time string from the helper function
    printf("The thread locale is now set to %s.\n",
           setlocale(LC_ALL, "English"));

    // Create the second thread.
    hThread = (HANDLE)_beginthreadex( NULL, 0, &SecondThreadFunc,
                                      NULL, 0, &threadID );

    if (get_time(str) == 0)
    {
        // Retrieve the time string from the helper function
        printf("The time in English locale is: '%s'\n\n", str);
    }

    // Wait for the created thread to finish.
    WaitForSingleObject( hThread, INFINITE );

    // Destroy the thread object.
    CloseHandle( hThread );
}

The thread locale is now set to English_United States.1252.
The time in English locale is: 'Wednesday, May 12, 2004'

The thread locale is now set to German_Germany.1252.
The time in German locale is: 'Mittwoch, 12. Mai 2004'