Re: Overwrite data_seg variable

From:

"Ben Voigt" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 24 Jan 2007 17:32:31 -0600

Message-ID:

<#FAF3#AQHHA.4280@TK2MSFTNGP02.phx.gbl>

"cleohm" <cleohm@discussions.microsoft.com> wrote in message
news:FE1B4565-6291-4B92-8EF7-A951BD67169E@microsoft.com...

Thanks for your reply. I did the following but still not working,
probably I
handle the variables incorrectly. Can help me identify them?

Hook.cpp

#pragma data_seg(".SHARDAT")
TCHAR szData[10]=_T("");

That's not valid, you should use a compound initializer with braces to
initialize a compound such as an array. Data in shared segments has to be
initialized according to certain rules:

http://msdn2.microsoft.com/en-us/library/h90dkhs0(VS.80).aspx

#pragma data_seg()

LRESULT __declspec(dllexport)__stdcall CALLBACK KeyboardProc(int nCode,
WPARAM wParam, LPARAM lParam)
{
CString strTxt = szData;
:
}

BOOL __declspec(dllexport)__stdcall InstallHook(LPCTSTR lpExternalData)
{
_tcscpy(szData, lpExternalData);
:
}

CDlg.cpp

void CDlg::Hook(LPCTSTR lpData)
{
static HINSTANCE hinstDLL = LoadLibrary(_T("Hook.dll"));
typedef BOOL (CALLBACK *inshook)(LPCTSTR);
inshook instkbhook = (inshook)GetProcAddress(hinstDLL, "InstallHook");
instkbhook(lpData);
ShowWindow(SW_MINIMIZE);
}

"Alex Blekhman" wrote:

"cleohm" wrote:

Thanks for your reply. The following list 2 codes
(Hook.cpp and CDlg.cpp):

Hook.cpp

#pragma data_seg(".SHARDAT")
static HHOOK hkb=NULL;
LPCTSTR lpData=_T("");
#pragma data_seg()

LRESULT __declspec(dllexport)__stdcall CALLBACK
KeyboardProc(int nCode,
WPARAM wParam, LPARAM lParam)
{
// Require the use of lpData here
return CallNextHookEx(hkb, nCode, wParam, lParam);
}

Just reread KB article KB100634 again.

<quote>
NOTE: If the block contains pointers, this can be a problem.
If the pointer holds the address of a variable not in the
shared data segment, this address is valid only in one
process space.
</quote>

You need to use shared array if you want to share whole
string:

#pragma data_seg(".SHARDAT")
TCHAR szData[42] = { 0 };
#pragma data_seg()

Alex