GetThreadContext Function (Windows)

MSDN Library
Win32 and COM Development
Diagnostics
Debugging and Error Handling
Basic Debugging
Debugging Reference
Debugging Functions

Syntax

C++

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BOOL WINAPI GetThreadContext(
  __in     HANDLE hThread,
  __inout  LPCONTEXT lpContext
);

Parameters

hThread [in]: A handle to the thread whose context is to be retrieved. The handle must have THREAD_GET_CONTEXT access to the thread. For more information, see Thread Security and Access Rights.

WOW64: The handle must also have THREAD_QUERY_INFORMATION access.
lpContext [in, out]: A pointer to a CONTEXT structure that receives the appropriate context of the specified thread. The value of the ContextFlags member of this structure specifies which portions of a thread's context are retrieved. The CONTEXT structure is highly processor specific. Refer to the WinNt.h header file for processor-specific definitions of this structures and any alignment requirements.

Return Value

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

This function is used to retrieve the thread context of the specified thread. The function retrieves a selective context based on the value of the ContextFlags member of the context structure. The thread identified by the hThread parameter is typically being debugged, but the function can also operate when the thread is not being debugged.

You cannot get a valid context for a running thread. Use the SuspendThread function to suspend the thread before calling GetThreadContext.

If you call GetThreadContext for the current thread, the function returns successfully; however, the context returned is not valid.

Requirements

Minimum supported client	Windows 2000 Professional
Minimum supported server	Windows 2000 Server
Header	Winbase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll

#include <windows.h>
#include <process.h>
#include <stdio.h>
#include <assert.h>

void mythreadfunc(void *data)
{
...

_exitthread();
}

void changeThreadState()
{
HANDLE thread = (HANDLE)_beginthread( mythreadfunc, 0, NULL );
CONTEXT context;
BOOL success;

SuspendThread(thread);

// get context
context.ContextFlags = (CONTEXT_FULL | CONTEXT_CONTROL);
success = GetThreadContext(thread, &context);
assert(success);
printf( "eax=%08X, ebx=%08X, ecx=%08X\n",
context.Eax, context.Ebx, context.Ecx );

// change context (dangerous, can crash program)
context.Eax = 0x1234BBBB;
context.Ecx = 0x2468ABCD;
success = SetThreadContext(thread, &context);
assert(success);

ResumeThread(thread);

// the resumed thread should see different values of eax, and ecx
}

Syntax

Parameters

Return Value

Remarks

Requirements

See Also