Article: Q304497
Product(s): Microsoft C Compiler
Version(s): 6.0
Operating System(s):
Keyword(s):
Last Modified: 13-MAY-2002
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The information in this article applies to:
- Microsoft Visual C++, 32-bit Editions, version 6.0
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SYMPTOMS
========
A heap corruption can occur if _wsetlocale is called simultaneously from
multiple threads.
CAUSE
=====
_wsetlocale does not synchronize access to a local static variable, outwlocale.
RESOLUTION
==========
To work around this, you must synchronize calls to _wsetlocale.
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.
MORE INFORMATION
================
The C Runtime locale mechanism in Microsoft Visual C++ is distinct from the
locale mechanism in Microsoft Windows. Though Windows supports per-thread
locales, C Runtime supports only a single global locale for any program.
If multiple threads call _wsetlocale, then no thread's locale can be trusted. For
example, if one thread calls _wsetlocale for French and tries to use that locale
for _wcslwr, and another thread calls _wsetlocale for English before the first
thread executes the _wcslwr function call, then the first thread uses the
English locale instead of the French locale.
Steps to Reproduce the Behavior
-------------------------------
#define _UNICODE
#include <stdio.h>
#include <locale.h>
#include <process.h>
void __cdecl test(void *i) {
_wsetlocale(LC_ALL, L"English");
_wsetlocale(LC_ALL, L"French");
_wsetlocale(LC_ALL, L"German");
_wsetlocale(LC_ALL, L"English");
printf("%d exit\n",i);
}
void wmain () {
for (int i=0; i<30; ++i) _beginthread(test,0,(void*)i);
getchar();
}
Additional query words:
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Keywords :
Technology : kbVCsearch kbAudDeveloper kbVC600 kbVC32bitSearch
Version : :6.0
Issue type : kbbug
Solution Type : kbfix
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