ShellExecute freezes on Windows XP when working with two processes - c++

Question

Imagine that you have two processes: one sends commands and working in administrative mode, another reads them and executes them.
bool SendMessage(const std::wstring& message, HANDLE pipe)
{
DWORD written = 0;
int bytesToSend = (message.size() + 1) * sizeof(wchar_t);
WriteFile(pipe, message.c_str(), bytesToSend, &written, nullptr); // WinAPI
return written == bytesToSend;
}
std::wstring ReadMessage(HANDLE pipe)
{
std::wstring message;
wchar_t wch;
DWORD bytesRead = 0;
while (true)
{
if (!ReadFile(pipe, &wch, sizeof(wch), &bytesRead, NULL) || !(bytesRead == sizeof(wch))) // WinAPI
{
message.clear();
break;
}
if (wch)
{
message += wch;
}
else
{
break;
}
}
return message;
}
void CommandLoop(HANDLE pipe)
{
DWORD dummy = 0;
WriteFile(pipe, "", 1, &dummy, NULL); //pass the token
while (true)
{
std::wstring command = ReadMessage(pipe);
if (command.empty())
break;
std::wstring file;
std::wstring params;
// Some handling here
// ...
// You are here
if (ParseCommand(command, file, params))
{
INT_PTR shellResult = reinterpret_cast<INT_PTR>(::ShellExecute(nullptr, L"open", file.c_str(), params.c_str(), nullptr, SW_SHOW)); /// freeze here
if (shellResult > HINSTANCE_ERROR)
{
SendMessage(L"ok", pipe);
}
else
{
SendMessage(std::to_wstring(shellResult), pipe);
}
}
}
}
From first process I send message with SendMessage for milliseconds. Second process spinning in CommandLoop.
Then I read this message in second process with ReadMessage for milliseconds. But when I call ShellExecute function in second process, this process freezes for 30 seconds only on Windows XP. On Windows 7, 8, 10 this code works correctly. What's could be wrong?

Answer 1

One common issue is virus scanners. Windows XP of course is long out of support, so performance on such systems is generally considered a non-issue. No makes of virus scanners is going to spend time making them faster on XP.