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Both the C Runtime Library and the Standard C++ Library provide support for changing the locale of your program. This topic discusses issues that arise when using the locale functionality of both libraries in a multithreaded application.
Remarks
With the C Runtime Library, you can create multithreaded applications using the _beginthread and _beginthreadex functions. This topic only covers multithreaded applications created using these functions. For more information, see
To change the locale using the C Runtime Library, use the _configthreadlocale(_ENABLE_PER_THREAD_LOCALE) in that thread. Conversely, calling _configthreadlocale(_DISABLE_PER_THREAD_LOCALE) will cause that thread to use the global locale, and any call to
To change the locale using the C++ Runtime Library, use the
 Note |
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Calling |
The following examples show how to use the
Calling setlocale in a Thread that Has Enabled Per Thread Locale
Example
In this example, the main thread spawns two child threads. The first thread, Thread A, enables per-thread locale by calling _configthreadlocale(_ENABLE_PER_THREAD_LOCALE). The second thread, Thread B, as well as the main thread, do not enable per-thread locale. Thread A then proceeds to change the locale using the
Since Thread A has per-thread locale enabled, only the C Runtime Library functions in Thread A start using the "french" locale. The C Runtime Library functions in Thread B and in the main thread continue to use the "C" locale. Also, since
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// multithread_locale_1.cpp
// compile with: /EHsc /MD
#include <clocale>
#include <cstdio>
#include <locale>
#include <process.h>
#include <windows.h>
#define NUM_THREADS 2
using namespace std;
unsigned __stdcall RunThreadA(void *params);
unsigned __stdcall RunThreadB(void *params);
BOOL localeSet = FALSE;
HANDLE printMutex = CreateMutex(NULL, FALSE, NULL);
int main()
{
HANDLE threads[NUM_THREADS];
unsigned aID;
threads[0] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadA, NULL, 0, &aID);
unsigned bID;
threads[1] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadB, NULL, 0, &bID);
WaitForMultipleObjects(2, threads, TRUE, INFINITE);
printf_s("[Thread main] Per-thread locale is NOT enabled.\n");
printf_s("[Thread main] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread main] locale::global is set to \"%s\"\n",
locale().name().c_str());
CloseHandle(threads[0]);
CloseHandle(threads[1]);
CloseHandle(printMutex);
return 0;
}
unsigned __stdcall RunThreadA(void *params)
{
_configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
setlocale(LC_ALL, "french");
localeSet = TRUE;
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread A] Per-thread locale is enabled.\n");
printf_s("[Thread A] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread A] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
}
unsigned __stdcall RunThreadB(void *params)
{
while (!localeSet)
Sleep(100);
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread B] Per-thread locale is NOT enabled.\n");
printf_s("[Thread B] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread B] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
} | |
Output
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[Thread A] Per-thread locale is enabled. [Thread A] CRT locale is set to "French_France.1252" [Thread A] locale::global is set to "C" [Thread B] Per-thread locale is NOT enabled. [Thread B] CRT locale is set to "C" [Thread B] locale::global is set to "C" [Thread main] Per-thread locale is NOT enabled. [Thread main] CRT locale is set to "C" [Thread main] locale::global is set to "C" | |
In this example, the main thread spawns two child threads. The first thread, Thread A, enables per-thread locale by calling _configthreadlocale(_ENABLE_PER_THREAD_LOCALE). The second thread, Thread B, as well as the main thread, do not enable per-thread locale. Thread A then proceeds to change the locale using the
Since Thread A has per-thread locale enabled, only the C Runtime Library functions in Thread A start using the "french" locale. The C Runtime Library functions in Thread B and in the main thread continue to use the "C" locale. However, since the
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// multithread_locale_2.cpp
// compile with: /EHsc /MD
#include <clocale>
#include <cstdio>
#include <locale>
#include <process.h>
#include <windows.h>
#define NUM_THREADS 2
using namespace std;
unsigned __stdcall RunThreadA(void *params);
unsigned __stdcall RunThreadB(void *params);
BOOL localeSet = FALSE;
HANDLE printMutex = CreateMutex(NULL, FALSE, NULL);
int main()
{
HANDLE threads[NUM_THREADS];
unsigned aID;
threads[0] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadA, NULL, 0, &aID);
unsigned bID;
threads[1] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadB, NULL, 0, &bID);
WaitForMultipleObjects(2, threads, TRUE, INFINITE);
printf_s("[Thread main] Per-thread locale is NOT enabled.\n");
printf_s("[Thread main] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread main] locale::global is set to \"%s\"\n",
locale().name().c_str());
CloseHandle(threads[0]);
CloseHandle(threads[1]);
CloseHandle(printMutex);
return 0;
}
unsigned __stdcall RunThreadA(void *params)
{
_configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
locale::global(locale("french"));
localeSet = TRUE;
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread A] Per-thread locale is enabled.\n");
printf_s("[Thread A] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread A] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
}
unsigned __stdcall RunThreadB(void *params)
{
while (!localeSet)
Sleep(100);
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread B] Per-thread locale is NOT enabled.\n");
printf_s("[Thread B] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread B] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
} | |
Output
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[Thread A] Per-thread locale is enabled. [Thread A] CRT locale is set to "French_France.1252" [Thread A] locale::global is set to "French_France.1252" [Thread B] Per-thread locale is NOT enabled. [Thread B] CRT locale is set to "C" [Thread B] locale::global is set to "French_France.1252" [Thread main] Per-thread locale is NOT enabled. [Thread main] CRT locale is set to "C" [Thread main] locale::global is set to "French_France.1252" | |
In this example, the main thread spawns two child threads. The first thread, Thread A, enables per-thread locale by calling _configthreadlocale(_ENABLE_PER_THREAD_LOCALE). The second thread, Thread B, as well as the main thread, do not enable per-thread locale. Thread B then proceeds to change the locale using the
Since Thread B does not have per-thread locale enabled, the C Runtime Library functions in Thread B and in the main thread start using the "french" locale. The C Runtime Library functions in Thread A continue to use the "C" locale because Thread A has per-thread locale enabled. Also, since
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// multithread_locale_3.cpp
// compile with: /EHsc /MD
#include <clocale>
#include <cstdio>
#include <locale>
#include <process.h>
#include <windows.h>
#define NUM_THREADS 2
using namespace std;
unsigned __stdcall RunThreadA(void *params);
unsigned __stdcall RunThreadB(void *params);
BOOL localeSet = FALSE;
HANDLE printMutex = CreateMutex(NULL, FALSE, NULL);
int main()
{
HANDLE threads[NUM_THREADS];
unsigned aID;
threads[0] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadA, NULL, 0, &aID);
unsigned bID;
threads[1] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadB, NULL, 0, &bID);
WaitForMultipleObjects(2, threads, TRUE, INFINITE);
printf_s("[Thread main] Per-thread locale is NOT enabled.\n");
printf_s("[Thread main] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread main] locale::global is set to \"%s\"\n",
locale().name().c_str());
CloseHandle(threads[0]);
CloseHandle(threads[1]);
CloseHandle(printMutex);
return 0;
}
unsigned __stdcall RunThreadA(void *params)
{
_configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
while (!localeSet)
Sleep(100);
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread A] Per-thread locale is enabled.\n");
printf_s("[Thread A] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread A] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
}
unsigned __stdcall RunThreadB(void *params)
{
setlocale(LC_ALL, "french");
localeSet = TRUE;
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread B] Per-thread locale is NOT enabled.\n");
printf_s("[Thread B] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread B] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
} | |
Output
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[Thread B] Per-thread locale is NOT enabled. [Thread B] CRT locale is set to "French_France.1252" [Thread B] locale::global is set to "C" [Thread A] Per-thread locale is enabled. [Thread A] CRT locale is set to "C" [Thread A] locale::global is set to "C" [Thread main] Per-thread locale is NOT enabled. [Thread main] CRT locale is set to "French_France.1252" [Thread main] locale::global is set to "C" | |
In this example, the main thread spawns two child threads. The first thread, Thread A, enables per-thread locale by calling _configthreadlocale(_ENABLE_PER_THREAD_LOCALE). The second thread, Thread B, as well as the main thread, do not enable per-thread locale. Thread B then proceeds to change the locale using the
Since Thread B does not have per-thread locale enabled, the C Runtime Library functions in Thread B and in the main thread start using the "french" locale. The C Runtime Library functions in Thread A continue to use the "C" locale because Thread A has per-thread locale enabled. However, since the
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// multithread_locale_4.cpp
// compile with: /EHsc /MD
#include <clocale>
#include <cstdio>
#include <locale>
#include <process.h>
#include <windows.h>
#define NUM_THREADS 2
using namespace std;
unsigned __stdcall RunThreadA(void *params);
unsigned __stdcall RunThreadB(void *params);
BOOL localeSet = FALSE;
HANDLE printMutex = CreateMutex(NULL, FALSE, NULL);
int main()
{
HANDLE threads[NUM_THREADS];
unsigned aID;
threads[0] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadA, NULL, 0, &aID);
unsigned bID;
threads[1] = (HANDLE)_beginthreadex(
NULL, 0, RunThreadB, NULL, 0, &bID);
WaitForMultipleObjects(2, threads, TRUE, INFINITE);
printf_s("[Thread main] Per-thread locale is NOT enabled.\n");
printf_s("[Thread main] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread main] locale::global is set to \"%s\"\n",
locale().name().c_str());
CloseHandle(threads[0]);
CloseHandle(threads[1]);
CloseHandle(printMutex);
return 0;
}
unsigned __stdcall RunThreadA(void *params)
{
_configthreadlocale(_ENABLE_PER_THREAD_LOCALE);
while (!localeSet)
Sleep(100);
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread A] Per-thread locale is enabled.\n");
printf_s("[Thread A] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread A] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
}
unsigned __stdcall RunThreadB(void *params)
{
locale::global(locale("french"));
localeSet = TRUE;
WaitForSingleObject(printMutex, INFINITE);
printf_s("[Thread B] Per-thread locale is NOT enabled.\n");
printf_s("[Thread B] CRT locale is set to \"%s\"\n",
setlocale(LC_ALL, NULL));
printf_s("[Thread B] locale::global is set to \"%s\"\n\n",
locale().name().c_str());
ReleaseMutex(printMutex);
return 1;
} | |
Output
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[Thread B] Per-thread locale is NOT enabled. [Thread B] CRT locale is set to "French_France.1252" [Thread B] locale::global is set to "French_France.1252" [Thread A] Per-thread locale is enabled. [Thread A] CRT locale is set to "C" [Thread A] locale::global is set to "French_France.1252" [Thread main] Per-thread locale is NOT enabled. [Thread main] CRT locale is set to "French_France.1252" [Thread main] locale::global is set to "French_France.1252" | |
Calling locale::global in a Thread that Has Enabled Per Thread Locale
Calling setlocale in a Thread that Has Not Enabled Per Thread Locale
Calling locale::global in a Thread that Has Not Enabled Per Thread Locale
See Also
Reference
Concepts
Multithreading