CreateProcess not able to throw an error when the executable file has an exception thrown at the very beginning

Question

There is an executable file and I am throwing an exception at the very beginning of the solution in program.cs. When loading this executable file from a different solution using CreateProcessA(), I see that the process loads and does not give me an error message. Any idea on how to catch this exception?

STARTUPINFOA startupInfo;
PROCESS_INFORMATION pi;
ZeroMemory(&startupInfo, sizeof(startupInfo));
startupInfo.cb = sizeof(startupInfo);
ZeroMemory(&pi, sizeof(pi));

const auto dwCreationFlags = showConsole ? CREATE_NEW_CONSOLE : CREATE_NO_WINDOW;
auto canCreate = true;
if (!CreateProcessA(
    nullptr,                                // LPCWSTR IpApplicationName
    const_cast<LPSTR>(command.c_str()),     // LPSTR IpCommandLine
    nullptr,                                // LPSECURITY_ATTRIBUTES IpProcessAttributes
    nullptr,                                // LPSECURITY_ATTRIBUTES IpThreadAttributes
    false,                                  // BOOL bInheritHandles,
    dwCreationFlags,                        // DWORD dwCreationFlags
    nullptr,                                // LPVOID IpEnvironment
    nullptr,                                // LPCWSTR IpCurrentDirectory
    &startupInfo,                           // LPSTARTUPINFOW IpStartupInfo
    &pi                                     // LPPROCESS_INFORMATION IpProcessInformation
))
{
    canCreate = false;
    return Status(WinUtil::GetLastErrorMessage());
}
//canCreate = false;

// Wait until child process exits.
WaitForSingleObject(pi.hProcess, 0);
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
return Status();

I am expecting it to return false and catch the exception.

However, it currently loops for a while, and then throws out a generic message saying that it failed to start. It's not catching the exception I threw at the very beginning of the solution.

Answer 1

You can't throw exceptions across language boundaries, let alone process boundaries. A C++ app cannot catch an exception thrown in a separate C# app.

When the C# app throws an exception that is not caught, it will simply terminate itself. The C++ app that launched it cannot catch that uncaught exception. The only thing it can do is wait for the C# app to terminate (which you are already doing), and then use GetExitCodeProcess() to get the exit code, which will be non-zero on an unexpected failure (such as 0xE0434352 for an uncaught managed exception, 0xC0000005 for an access violation, 0xC00000FD for a stack overflow, etc).

See: Exit Code When Unhandled Exception Terminates Execution?