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POWin32 WriteProcessMemory() magical offset value
 

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    <p>I'm trying to read the data in a Win32 ListView owned by another process. Unfortunately, my WriteProcessMemory() call fails with the error "This function is not supported on this system." when I specify "NULL" for the base address in my VirtualAlloc() call. If, however, I offset that VirtualAlloc() address by some "magic" value that I got lucky with and picked at random during a moment of frustration, the call works on my system, but fails on other ones. (see the code below)</p> <p>Can anybody suggest what this magical offset is doing for me? By trial and error, I can find values that work on specific systems, but I can't find a general solution to this problem.</p> <p>Thanks, PaulH</p> <pre><code>#define MAGIC_OFFSET (DWORD)0x01020000 LVHITTESTINFO hti = { 0 }; hti.pt = clientPoint; LPVOID lpBuffer = ::VirtualAlloc( NULL, 1, MEM_RESERVE, PAGE_READWRITE ); ::VirtualFree( lpBuffer, 0, MEM_RELEASE ); lpBuffer = ::VirtualAlloc( (LPVOID)((DWORD)lpBuffer + MAGIC_OFFSET), sizeof( hti ), MEM_RESERVER, PAGE_READWRITE ); DWORD dwBuffer = (DWORD)lpBuffer + MAGIC_OFFSET - sizeof( hti ); if( !::WriteProcessMemory( hProcess, (LPVOID)dwBuffer, (LPVOID)&amp;hti, sizeof( hti ), NULL ) ) return 0; if( ListView_HitTest( hWndListView, (LPVOID)dwBuffer ) &lt; 0 ) return 0; if( !::ReadProcessMemory( hProcess, (LPVOID)dwBuffer, (LPVOID)&amp;hti, sizeof( hti ), NULL ) ) return 0; ::VirtualFree( lpBuffer, 0, MEM_RELEASE ); </code></pre> <p>Clarification (added by Cd-MaN): this is on a Windows Mobile platform, probably non-x86 architecture. So the situation may be different (are there separate address spaces in ARM processors?).</p>
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