Modules/_winapi.c

Source:

cpython 3.14 @ ab2d84fe1023/Modules/_winapi.c ↗

_winapi provides the low-level Windows API bindings used by subprocess on Windows. It is a Windows-only C extension.

Map

Lines	Symbol	Role
1-80	HANDLE type	Python object wrapping a Windows HANDLE
81-200	CreateProcess	Spawn a process with I/O redirection
201-350	CreatePipe	Create an anonymous pipe: returns (read_handle, write_handle)
351-500	WaitForSingleObject	Block until a handle is signaled or timeout
501-650	GetExitCodeProcess	Return process exit code
651-800	CloseHandle	Release a Windows HANDLE
801-1400	Named pipe API	CreateNamedPipe, ConnectNamedPipe, WaitNamedPipe

Reading

CreateProcess

// CPython: Modules/_winapi.c:300 winapi_CreateProcess_impl
static PyObject *
winapi_CreateProcess_impl(PyObject *module, LPCWSTR application_name,
                          LPWSTR command_line, ...)
{
    STARTUPINFOEXW si;
    PROCESS_INFORMATION pi;
    ZeroMemory(&si, sizeof(si));
    si.StartupInfo.cb = sizeof(si);
    si.StartupInfo.hStdInput  = stdin_handle;
    si.StartupInfo.hStdOutput = stdout_handle;
    si.StartupInfo.hStdError  = stderr_handle;
    si.StartupInfo.dwFlags   |= STARTF_USESTDHANDLES;

    Py_BEGIN_ALLOW_THREADS
    BOOL ret = CreateProcessW(application_name, command_line, NULL, NULL,
                              TRUE,  /* inherit handles */
                              creation_flags,
                              environment, current_directory,
                              (LPSTARTUPINFOW)&si, &pi);
    Py_END_ALLOW_THREADS
    if (!ret)
        return PyErr_SetFromWindowsErr(GetLastError());
    return Py_BuildValue("NNkk",
        HANDLE_TO_PYNUM(pi.hProcess),
        HANDLE_TO_PYNUM(pi.hThread),
        pi.dwProcessId,
        pi.dwThreadId);
}

CreatePipe

// CPython: Modules/_winapi.c:410 winapi_CreatePipe_impl
static PyObject *
winapi_CreatePipe_impl(PyObject *module, PyObject *pipe_attrs, DWORD size)
{
    HANDLE read_pipe, write_pipe;
    if (!CreatePipe(&read_pipe, &write_pipe,
                    (LPSECURITY_ATTRIBUTES)pipe_attrs, size))
        return PyErr_SetFromWindowsErr(GetLastError());
    return Py_BuildValue("NN",
        HANDLE_TO_PYNUM(read_pipe),
        HANDLE_TO_PYNUM(write_pipe));
}

subprocess.Popen uses CreatePipe to set up stdin/stdout/stderr redirection.

WaitForSingleObject

// CPython: Modules/_winapi.c:540 winapi_WaitForSingleObject_impl
static PyObject *
winapi_WaitForSingleObject_impl(PyObject *module, HANDLE handle, DWORD milliseconds)
{
    DWORD result;
    Py_BEGIN_ALLOW_THREADS
    result = WaitForSingleObject(handle, milliseconds);
    Py_END_ALLOW_THREADS
    if (result == WAIT_FAILED)
        return PyErr_SetFromWindowsErr(GetLastError());
    return PyLong_FromUnsignedLong(result);
}

Returns WAIT_OBJECT_0 (0) when the handle is signaled, WAIT_TIMEOUT on timeout.

gopy notes

_winapi is Windows-only. gopy builds for Linux/macOS by default. On Windows, _winapi is in module/_winapi/module_windows.go using Go's syscall package for CreateProcess, CreatePipe, and WaitForSingleObject. HANDLE is an uintptr in Go.