gh-112984 Update Windows build and installer for free-threaded builds (GH-113129)

6 files changed, 639 insertions, 31 deletions

diff --git a/PC/layout/main.py b/PC/layout/main.py
index accfd51..d176b27 100644
--- a/PC/layout/main.py
+++ b/PC/layout/main.py
@@ -41,7 +41,7 @@ TCLTK_FILES_ONLY = FileNameSet("turtle.py")
 
 VENV_DIRS_ONLY = FileNameSet("venv", "ensurepip")
 
-EXCLUDE_FROM_PYDS = FileStemSet("python*", "pyshellext", "vcruntime*")
+EXCLUDE_FROM_DLLS = FileStemSet("python*", "pyshellext", "vcruntime*")
 EXCLUDE_FROM_LIB = FileNameSet("*.pyc", "__pycache__", "*.pickle")
 EXCLUDE_FROM_PACKAGED_LIB = FileNameSet("readme.txt")
 EXCLUDE_FROM_COMPILE = FileNameSet("badsyntax_*", "bad_*")
@@ -126,9 +126,9 @@ def get_layout(ns):
         n = new_name or n
         src = ns.build / f
         if ns.debug and src not in REQUIRED_DLLS:
-            if not src.stem.endswith("_d"):
+            if not "_d." in src.name:
                 src = src.parent / (src.stem + "_d" + src.suffix)
-            if not n.endswith("_d"):
+            if "_d." not in f:
                 n += "_d"
                 f = n + "." + x
         yield dest + n + "." + x, src
@@ -141,17 +141,45 @@ def get_layout(ns):
             if lib.is_file():
                 yield "libs/" + n + ".lib", lib
 
+    source = "python.exe"
+    sourcew = "pythonw.exe"
+    alias = [
+        "python",
+        "python{}".format(VER_MAJOR) if ns.include_alias3 else "",
+        "python{}".format(VER_DOT) if ns.include_alias3x else "",
+    ]
+    aliasw = [
+        "pythonw",
+        "pythonw{}".format(VER_MAJOR) if ns.include_alias3 else "",
+        "pythonw{}".format(VER_DOT) if ns.include_alias3x else "",
+    ]
     if ns.include_appxmanifest:
-        yield from in_build("python_uwp.exe", new_name="python{}".format(VER_DOT))
-        yield from in_build("pythonw_uwp.exe", new_name="pythonw{}".format(VER_DOT))
-        # For backwards compatibility, but we don't reference these ourselves.
-        yield from in_build("python_uwp.exe", new_name="python")
-        yield from in_build("pythonw_uwp.exe", new_name="pythonw")
+        source = "python_uwp.exe"
+        sourcew = "pythonw_uwp.exe"
+    elif ns.include_freethreaded:
+        source = "python{}t.exe".format(VER_DOT)
+        sourcew = "pythonw{}t.exe".format(VER_DOT)
+        if not ns.include_alias:
+            alias = []
+            aliasw = []
+        alias.extend([
+            "python{}t".format(VER_DOT),
+            "python{}t".format(VER_MAJOR) if ns.include_alias3 else None,
+        ])
+        aliasw.extend([
+            "pythonw{}t".format(VER_DOT),
+            "pythonw{}t".format(VER_MAJOR) if ns.include_alias3 else None,
+        ])
+
+    for a in filter(None, alias):
+        yield from in_build(source, new_name=a)
+    for a in filter(None, aliasw):
+        yield from in_build(sourcew, new_name=a)
+
+    if ns.include_freethreaded:
+        yield from in_build(FREETHREADED_PYTHON_DLL_NAME)
     else:
-        yield from in_build("python.exe", new_name="python")
-        yield from in_build("pythonw.exe", new_name="pythonw")
-
-    yield from in_build(PYTHON_DLL_NAME)
+        yield from in_build(PYTHON_DLL_NAME)
 
     if ns.include_launchers and ns.include_appxmanifest:
         if ns.include_pip:
@@ -160,7 +188,10 @@ def get_layout(ns):
             yield from in_build("pythonw_uwp.exe", new_name="idle{}".format(VER_DOT))
 
     if ns.include_stable:
-        yield from in_build(PYTHON_STABLE_DLL_NAME)
+        if ns.include_freethreaded:
+            yield from in_build(FREETHREADED_PYTHON_STABLE_DLL_NAME)
+        else:
+            yield from in_build(PYTHON_STABLE_DLL_NAME)
 
     found_any = False
     for dest, src in rglob(ns.build, "vcruntime*.dll"):
@@ -171,16 +202,28 @@ def get_layout(ns):
 
     yield "LICENSE.txt", ns.build / "LICENSE.txt"
 
-    for dest, src in rglob(ns.build, ("*.pyd", "*.dll")):
-        if src.stem.endswith("_d") != bool(ns.debug) and src not in REQUIRED_DLLS:
-            continue
-        if src in EXCLUDE_FROM_PYDS:
-            continue
+    for dest, src in rglob(ns.build, "*.pyd"):
+        if ns.include_freethreaded:
+            if not src.match("*.cp*t-win*.pyd"):
+                continue
+            if bool(src.match("*_d.cp*.pyd")) != bool(ns.debug):
+                continue
+        else:
+            if src.match("*.cp*t-win*.pyd"):
+                continue
+            if bool(src.match("*_d.pyd")) != bool(ns.debug):
+                continue
         if src in TEST_PYDS_ONLY and not ns.include_tests:
             continue
         if src in TCLTK_PYDS_ONLY and not ns.include_tcltk:
             continue
+        yield from in_build(src.name, dest="" if ns.flat_dlls else "DLLs/")
 
+    for dest, src in rglob(ns.build, "*.dll"):
+        if src.stem.endswith("_d") != bool(ns.debug) and src not in REQUIRED_DLLS:
+            continue
+        if src in EXCLUDE_FROM_DLLS:
+            continue
         yield from in_build(src.name, dest="" if ns.flat_dlls else "DLLs/")
 
     if ns.zip_lib:
@@ -191,8 +234,12 @@ def get_layout(ns):
             yield "Lib/{}".format(dest), src
 
         if ns.include_venv:
-            yield from in_build("venvlauncher.exe", "Lib/venv/scripts/nt/", "python")
-            yield from in_build("venvwlauncher.exe", "Lib/venv/scripts/nt/", "pythonw")
+            if ns.include_freethreaded:
+                yield from in_build("venvlaunchert.exe", "Lib/venv/scripts/nt/")
+                yield from in_build("venvwlaunchert.exe", "Lib/venv/scripts/nt/")
+            else:
+                yield from in_build("venvlauncher.exe", "Lib/venv/scripts/nt/")
+                yield from in_build("venvwlauncher.exe", "Lib/venv/scripts/nt/")
 
     if ns.include_tools:
 
@@ -208,7 +255,6 @@ def get_layout(ns):
         yield PYTHON_PTH_NAME, ns.temp / PYTHON_PTH_NAME
 
     if ns.include_dev:
-
         for dest, src in rglob(ns.source / "Include", "**/*.h"):
             yield "include/{}".format(dest), src
         yield "include/pyconfig.h", ns.build / "pyconfig.h"
@@ -552,7 +598,6 @@ def main():
 
     ns.source = ns.source or (Path(__file__).resolve().parent.parent.parent)
     ns.build = ns.build or Path(sys.executable).parent
-    ns.temp = ns.temp or Path(tempfile.mkdtemp())
     ns.doc_build = ns.doc_build or (ns.source / "Doc" / "build")
     if not ns.source.is_absolute():
         ns.source = (Path.cwd() / ns.source).resolve()
@@ -565,7 +610,12 @@ def main():
     if ns.include_cat and not ns.include_cat.is_absolute():
         ns.include_cat = (Path.cwd() / ns.include_cat).resolve()
     if not ns.arch:
-        ns.arch = "amd64" if sys.maxsize > 2 ** 32 else "win32"
+        if sys.winver.endswith("-arm64"):
+            ns.arch = "arm64"
+        elif sys.winver.endswith("-32"):
+            ns.arch = "win32"
+        else:
+            ns.arch = "amd64"
 
     if ns.copy and not ns.copy.is_absolute():
         ns.copy = (Path.cwd() / ns.copy).resolve()
@@ -574,6 +624,14 @@ def main():
     if ns.catalog and not ns.catalog.is_absolute():
         ns.catalog = (Path.cwd() / ns.catalog).resolve()
 
+    if not ns.temp:
+        # Put temp on a Dev Drive for speed if we're copying to one.
+        # If not, the regular temp dir will have to do.
+        if ns.copy and getattr(os.path, "isdevdrive", lambda d: False)(ns.copy):
+            ns.temp = ns.copy.with_name(ns.copy.name + "_temp")
+        else:
+            ns.temp = Path(tempfile.mkdtemp())
+
     configure_logger(ns)
 
     log_info(
@@ -602,6 +660,12 @@ Catalog: {ns.catalog}""",
         log_warning("Assuming --include-tcltk to support --include-idle")
         ns.include_tcltk = True
 
+    if not (ns.include_alias or ns.include_alias3 or ns.include_alias3x):
+        if ns.include_freethreaded:
+            ns.include_alias3x = True
+        else:
+            ns.include_alias = True
+
     try:
         generate_source_files(ns)
         files = list(get_layout(ns))
diff --git a/PC/layout/support/constants.py b/PC/layout/support/constants.py
index 8195c3d..ae22aa1 100644
--- a/PC/layout/support/constants.py
+++ b/PC/layout/support/constants.py
@@ -39,3 +39,6 @@ PYTHON_PTH_NAME = "python{}{}._pth".format(VER_MAJOR, VER_MINOR)
 PYTHON_CHM_NAME = "python{}{}{}{}.chm".format(
     VER_MAJOR, VER_MINOR, VER_MICRO, VER_SUFFIX
 )
+
+FREETHREADED_PYTHON_DLL_NAME = "python{}{}t.dll".format(VER_MAJOR, VER_MINOR)
+FREETHREADED_PYTHON_STABLE_DLL_NAME = "python{}t.dll".format(VER_MAJOR)
diff --git a/PC/layout/support/nuspec.py b/PC/layout/support/nuspec.py
index dbcb713..a87e0be 100644
--- a/PC/layout/support/nuspec.py
+++ b/PC/layout/support/nuspec.py
@@ -24,6 +24,10 @@ NUSPEC_PLATFORM_DATA = dict(
     amd64=("64-bit", "python", "Python"),
     arm32=("ARM", "pythonarm", "Python (ARM)"),
     arm64=("ARM64", "pythonarm64", "Python (ARM64)"),
+    win32t=("32-bit free-threaded", "pythonx86-freethreaded", "Python (32-bit, free-threaded)"),
+    amd64t=("64-bit free-threaded", "python-freethreaded", "Python (free-threaded)"),
+    arm32t=("ARM free-threaded", "pythonarm-freethreaded", "Python (ARM, free-threaded)"),
+    arm64t=("ARM64 free-threaded", "pythonarm64-freethreaded", "Python (ARM64, free-threaded)"),
 )
 
 if not NUSPEC_DATA["PYTHON_VERSION"]:
@@ -58,7 +62,10 @@ NUSPEC_TEMPLATE = r"""<?xml version="1.0"?>
 
 
 def _get_nuspec_data_overrides(ns):
-    for k, v in zip(NUSPEC_PLATFORM_DATA["_keys"], NUSPEC_PLATFORM_DATA[ns.arch]):
+    arch = ns.arch
+    if ns.include_freethreaded:
+        arch += "t"
+    for k, v in zip(NUSPEC_PLATFORM_DATA["_keys"], NUSPEC_PLATFORM_DATA[arch]):
         ev = os.getenv("PYTHON_NUSPEC_" + k)
         if ev:
             yield k, ev
diff --git a/PC/layout/support/options.py b/PC/layout/support/options.py
index 60256fb..f1a8eb0 100644
--- a/PC/layout/support/options.py
+++ b/PC/layout/support/options.py
@@ -32,6 +32,10 @@ OPTIONS = {
     "nuspec": {"help": "a python.nuspec file"},
     "chm": {"help": "the CHM documentation"},
     "html-doc": {"help": "the HTML documentation"},
+    "freethreaded": {"help": "freethreaded binaries", "not-in-all": True},
+    "alias": {"help": "aliased python.exe entry-point binaries"},
+    "alias3": {"help": "aliased python3.exe entry-point binaries"},
+    "alias3x": {"help": "aliased python3.x.exe entry-point binaries"},
 }
 
 
@@ -47,6 +51,8 @@ PRESETS = {
             "dev",
             "launchers",
             "appxmanifest",
+            "alias",
+            "alias3x",
             # XXX: Disabled for now "precompile",
         ],
     },
@@ -59,9 +65,10 @@ PRESETS = {
             "venv",
             "props",
             "nuspec",
+            "alias",
         ],
     },
-    "iot": {"help": "Windows IoT Core", "options": ["stable", "pip"]},
+    "iot": {"help": "Windows IoT Core", "options": ["alias", "stable", "pip"]},
     "default": {
         "help": "development kit package",
         "options": [
@@ -74,11 +81,19 @@ PRESETS = {
             "dev",
             "symbols",
             "html-doc",
+            "alias",
         ],
     },
     "embed": {
         "help": "embeddable package",
-        "options": ["stable", "zip-lib", "flat-dlls", "underpth", "precompile"],
+        "options": [
+            "alias",
+            "stable",
+            "zip-lib",
+            "flat-dlls",
+            "underpth",
+            "precompile",
+        ],
     },
 }
 
diff --git a/PC/pyconfig.h.in b/PC/pyconfig.h.in
index d8f0a6b..8bbf877 100644
--- a/PC/pyconfig.h.in
+++ b/PC/pyconfig.h.in
@@ -94,6 +94,9 @@ WIN32 is still required for the locale module.
 #endif
 #endif /* Py_BUILD_CORE || Py_BUILD_CORE_BUILTIN || Py_BUILD_CORE_MODULE */
 
+/* Define to 1 if you want to disable the GIL */
+#undef Py_GIL_DISABLED
+
 /* Compiler specific defines */
 
 /* ------------------------------------------------------------------------*/
@@ -305,8 +308,16 @@ Py_NO_ENABLE_SHARED to find out.  Also support MS_NO_COREDLL for b/w compat */
                 /* not building the core - must be an ext */
 #               if defined(_MSC_VER)
                         /* So MSVC users need not specify the .lib
-                        file in their Makefile (other compilers are
-                        generally taken care of by distutils.) */
+                        file in their Makefile */
+#                       if defined(Py_GIL_DISABLED)
+#                       if defined(_DEBUG)
+#                               pragma comment(lib,"python313t_d.lib")
+#                       elif defined(Py_LIMITED_API)
+#                               pragma comment(lib,"python3t.lib")
+#                       else
+#                               pragma comment(lib,"python313t.lib")
+#                       endif /* _DEBUG */
+#                       else /* Py_GIL_DISABLED */
 #                       if defined(_DEBUG)
 #                               pragma comment(lib,"python313_d.lib")
 #                       elif defined(Py_LIMITED_API)
@@ -314,6 +325,7 @@ Py_NO_ENABLE_SHARED to find out.  Also support MS_NO_COREDLL for b/w compat */
 #                       else
 #                               pragma comment(lib,"python313.lib")
 #                       endif /* _DEBUG */
+#                       endif /* Py_GIL_DISABLED */
 #               endif /* _MSC_VER */
 #       endif /* Py_BUILD_CORE */
 #endif /* MS_COREDLL */
@@ -739,7 +751,4 @@ Py_NO_ENABLE_SHARED to find out.  Also support MS_NO_COREDLL for b/w compat */
 /* Define if libssl has X509_VERIFY_PARAM_set1_host and related function */
 #define HAVE_X509_VERIFY_PARAM_SET1_HOST 1
 
-/* Define if you want to disable the GIL */
-#undef Py_GIL_DISABLED
-
 #endif /* !Py_CONFIG_H */
diff --git a/PC/venvlauncher.c b/PC/venvlauncher.c
new file mode 100644
index 0000000..fe97d32
--- /dev/null
+++ b/PC/venvlauncher.c
@@ -0,0 +1,510 @@
+/*
+ * venv redirector for Windows
+ *
+ * This launcher looks for a nearby pyvenv.cfg to find the correct home
+ * directory, and then launches the original Python executable from it.
+ * The name of this executable is passed as argv[0].
+ */
+
+#define __STDC_WANT_LIB_EXT1__ 1
+
+#include <windows.h>
+#include <pathcch.h>
+#include <fcntl.h>
+#include <io.h>
+#include <shlobj.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <tchar.h>
+#include <assert.h>
+
+#define MS_WINDOWS
+#include "patchlevel.h"
+
+#define MAXLEN PATHCCH_MAX_CCH
+#define MSGSIZE 1024
+
+#define RC_NO_STD_HANDLES   100
+#define RC_CREATE_PROCESS   101
+#define RC_NO_PYTHON        103
+#define RC_NO_MEMORY        104
+#define RC_NO_VENV_CFG      106
+#define RC_BAD_VENV_CFG     107
+#define RC_NO_COMMANDLINE   108
+#define RC_INTERNAL_ERROR   109
+
+// This should always be defined when we build for real,
+// but it's handy to have a definition for quick testing
+#ifndef EXENAME
+#define EXENAME L"python.exe"
+#endif
+
+#ifndef CFGNAME
+#define CFGNAME L"pyvenv.cfg"
+#endif
+
+static FILE * log_fp = NULL;
+
+void
+debug(wchar_t * format, ...)
+{
+    va_list va;
+
+    if (log_fp != NULL) {
+        wchar_t buffer[MAXLEN];
+        int r = 0;
+        va_start(va, format);
+        r = vswprintf_s(buffer, MAXLEN, format, va);
+        va_end(va);
+
+        if (r <= 0) {
+            return;
+        }
+        fwprintf(log_fp, L"%ls\n", buffer);
+        while (r && isspace(buffer[r])) {
+            buffer[r--] = L'\0';
+        }
+        if (buffer[0]) {
+            OutputDebugStringW(buffer);
+        }
+    }
+}
+
+
+void
+formatWinerror(int rc, wchar_t * message, int size)
+{
+    FormatMessageW(
+        FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+        NULL, rc, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+        message, size, NULL);
+}
+
+
+void
+winerror(int err, wchar_t * format, ... )
+{
+    va_list va;
+    wchar_t message[MSGSIZE];
+    wchar_t win_message[MSGSIZE];
+    int len;
+
+    if (err == 0) {
+        err = GetLastError();
+    }
+
+    va_start(va, format);
+    len = _vsnwprintf_s(message, MSGSIZE, _TRUNCATE, format, va);
+    va_end(va);
+
+    formatWinerror(err, win_message, MSGSIZE);
+    if (len >= 0) {
+        _snwprintf_s(&message[len], MSGSIZE - len, _TRUNCATE, L": %ls",
+                     win_message);
+    }
+
+#if !defined(_WINDOWS)
+    fwprintf(stderr, L"%ls\n", message);
+#else
+    MessageBoxW(NULL, message, L"Python venv launcher is sorry to say ...",
+               MB_OK);
+#endif
+}
+
+
+void
+error(wchar_t * format, ... )
+{
+    va_list va;
+    wchar_t message[MSGSIZE];
+
+    va_start(va, format);
+    _vsnwprintf_s(message, MSGSIZE, _TRUNCATE, format, va);
+    va_end(va);
+
+#if !defined(_WINDOWS)
+    fwprintf(stderr, L"%ls\n", message);
+#else
+    MessageBoxW(NULL, message, L"Python venv launcher is sorry to say ...",
+               MB_OK);
+#endif
+}
+
+
+bool
+isEnvVarSet(const wchar_t *name)
+{
+    /* only looking for non-empty, which means at least one character
+       and the null terminator */
+    return GetEnvironmentVariableW(name, NULL, 0) >= 2;
+}
+
+
+bool
+join(wchar_t *buffer, size_t bufferLength, const wchar_t *fragment)
+{
+    if (SUCCEEDED(PathCchCombineEx(buffer, bufferLength, buffer, fragment, PATHCCH_ALLOW_LONG_PATHS))) {
+        return true;
+    }
+    return false;
+}
+
+
+bool
+split_parent(wchar_t *buffer, size_t bufferLength)
+{
+    return SUCCEEDED(PathCchRemoveFileSpec(buffer, bufferLength));
+}
+
+
+/*
+ * Path calculation
+ */
+
+int
+calculate_pyvenvcfg_path(wchar_t *pyvenvcfg_path, size_t maxlen)
+{
+    if (!pyvenvcfg_path) {
+        error(L"invalid buffer provided");
+        return RC_INTERNAL_ERROR;
+    }
+    if ((DWORD)maxlen != maxlen) {
+        error(L"path buffer is too large");
+        return RC_INTERNAL_ERROR;
+    }
+    if (!GetModuleFileNameW(NULL, pyvenvcfg_path, (DWORD)maxlen)) {
+        winerror(GetLastError(), L"failed to read executable directory");
+        return RC_NO_COMMANDLINE;
+    }
+    // Remove 'python.exe' from our path
+    if (!split_parent(pyvenvcfg_path, maxlen)) {
+        error(L"failed to remove segment from '%ls'", pyvenvcfg_path);
+        return RC_NO_COMMANDLINE;
+    }
+    // Replace with 'pyvenv.cfg'
+    if (!join(pyvenvcfg_path, maxlen, CFGNAME)) {
+        error(L"failed to append '%ls' to '%ls'", CFGNAME, pyvenvcfg_path);
+        return RC_NO_MEMORY;
+    }
+    // If it exists, return
+    if (GetFileAttributesW(pyvenvcfg_path) != INVALID_FILE_ATTRIBUTES) {
+        return 0;
+    }
+    // Otherwise, remove 'pyvenv.cfg' and (probably) 'Scripts'
+    if (!split_parent(pyvenvcfg_path, maxlen) ||
+        !split_parent(pyvenvcfg_path, maxlen)) {
+        error(L"failed to remove segments from '%ls'", pyvenvcfg_path);
+        return RC_NO_COMMANDLINE;
+    }
+    // Replace 'pyvenv.cfg'
+    if (!join(pyvenvcfg_path, maxlen, CFGNAME)) {
+        error(L"failed to append '%ls' to '%ls'", CFGNAME, pyvenvcfg_path);
+        return RC_NO_MEMORY;
+    }
+    // If it exists, return
+    if (GetFileAttributesW(pyvenvcfg_path) != INVALID_FILE_ATTRIBUTES) {
+        return 0;
+    }
+    // Otherwise, we fail
+    winerror(GetLastError(), L"failed to locate %ls", CFGNAME);
+    return RC_NO_VENV_CFG;
+}
+
+
+/*
+ * pyvenv.cfg parsing
+ */
+
+static int
+find_home_value(const char *buffer, DWORD maxlen, const char **start, DWORD *length)
+{
+    if (!buffer || !start || !length) {
+        error(L"invalid find_home_value parameters()");
+        return 0;
+    }
+    for (const char *s = strstr(buffer, "home");
+         s && ((ptrdiff_t)s - (ptrdiff_t)buffer) < maxlen;
+         s = strstr(s + 1, "\nhome")
+    ) {
+        if (*s == '\n') {
+            ++s;
+        }
+        for (int i = 4; i > 0 && *s; --i, ++s);
+
+        while (*s && iswspace(*s)) {
+            ++s;
+        }
+        if (*s != L'=') {
+            continue;
+        }
+
+        do {
+            ++s;
+        } while (*s && iswspace(*s));
+
+        *start = s;
+        char *nl = strchr(s, '\n');
+        if (nl) {
+            while (nl != s && iswspace(nl[-1])) {
+                --nl;
+            }
+            *length = (DWORD)((ptrdiff_t)nl - (ptrdiff_t)s);
+        } else {
+            *length = (DWORD)strlen(s);
+        }
+        return 1;
+    }
+    return 0;
+}
+
+
+int
+read_home(const wchar_t *pyvenv_cfg, wchar_t *home_path, size_t maxlen)
+{
+    HANDLE hFile = CreateFileW(pyvenv_cfg, GENERIC_READ,
+        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+        NULL, OPEN_EXISTING, 0, NULL);
+
+    if (hFile == INVALID_HANDLE_VALUE) {
+        winerror(GetLastError(), L"failed to open '%ls'", pyvenv_cfg);
+        return RC_BAD_VENV_CFG;
+    }
+
+    // 8192 characters ought to be enough for anyone
+    // (doubled compared to the old implementation!)
+    char buffer[8192];
+    DWORD len;
+    if (!ReadFile(hFile, buffer, sizeof(buffer) - 1, &len, NULL)) {
+        winerror(GetLastError(), L"failed to read '%ls'", pyvenv_cfg);
+        CloseHandle(hFile);
+        return RC_BAD_VENV_CFG;
+    }
+    CloseHandle(hFile);
+    // Ensure null termination
+    buffer[len] = '\0';
+
+    char *home;
+    DWORD home_len;
+    if (!find_home_value(buffer, sizeof(buffer), &home, &home_len)) {
+        error(L"no home= specified in '%ls'", pyvenv_cfg);
+        return RC_BAD_VENV_CFG;
+    }
+
+    if ((DWORD)maxlen != maxlen) {
+        maxlen = 8192;
+    }
+    len = MultiByteToWideChar(CP_UTF8, 0, home, home_len, home_path, (DWORD)maxlen);
+    if (!len) {
+        winerror(GetLastError(), L"failed to decode home setting in '%ls'", pyvenv_cfg);
+        return RC_BAD_VENV_CFG;
+    }
+    home_path[len] = L'\0';
+
+    return 0;
+}
+
+
+int
+locate_python(wchar_t *path, size_t maxlen)
+{
+    if (!join(path, maxlen, EXENAME)) {
+        error(L"failed to append %ls to '%ls'", EXENAME, path);
+        return RC_NO_MEMORY;
+    }
+
+    if (GetFileAttributesW(path) == INVALID_FILE_ATTRIBUTES) {
+        winerror(GetLastError(), L"did not find executable at '%ls'", path);
+        return RC_NO_PYTHON;
+    }
+
+    return 0;
+}
+
+
+int
+smuggle_path()
+{
+    wchar_t buffer[MAXLEN];
+    // We could use argv[0], but that may be wrong in certain rare cases (if the
+    // user is doing something weird like symlinks to venv redirectors), and
+    // what we _really_ want is the directory of the venv. We always copy the
+    // redirectors, so if we've made the venv, this will be correct.
+    DWORD len = GetModuleFileNameW(NULL, buffer, MAXLEN);
+    if (!len) {
+        winerror(GetLastError(), L"Failed to get own executable path");
+        return RC_INTERNAL_ERROR;
+    }
+    buffer[len] = L'\0';
+    debug(L"Setting __PYVENV_LAUNCHER__ = '%s'", buffer);
+
+    if (!SetEnvironmentVariableW(L"__PYVENV_LAUNCHER__", buffer)) {
+        winerror(GetLastError(), L"Failed to set launcher environment");
+        return RC_INTERNAL_ERROR;
+    }
+
+    return 0;
+}
+
+/*
+ * Process creation
+ */
+
+static BOOL
+safe_duplicate_handle(HANDLE in, HANDLE * pout, const wchar_t *name)
+{
+    BOOL ok;
+    HANDLE process = GetCurrentProcess();
+    DWORD rc;
+
+    *pout = NULL;
+    ok = DuplicateHandle(process, in, process, pout, 0, TRUE,
+                         DUPLICATE_SAME_ACCESS);
+    if (!ok) {
+        rc = GetLastError();
+        if (rc == ERROR_INVALID_HANDLE) {
+            debug(L"DuplicateHandle(%ls) returned ERROR_INVALID_HANDLE\n", name);
+            ok = TRUE;
+        }
+        else {
+            debug(L"DuplicateHandle(%ls) returned %d\n", name, rc);
+        }
+    }
+    return ok;
+}
+
+static BOOL WINAPI
+ctrl_c_handler(DWORD code)
+{
+    return TRUE;    /* We just ignore all control events. */
+}
+
+static int
+launch(const wchar_t *executable, wchar_t *cmdline)
+{
+    HANDLE job;
+    JOBOBJECT_EXTENDED_LIMIT_INFORMATION info;
+    DWORD rc;
+    BOOL ok;
+    STARTUPINFOW si;
+    PROCESS_INFORMATION pi;
+
+#if defined(_WINDOWS)
+    /*
+    When explorer launches a Windows (GUI) application, it displays
+    the "app starting" (the "pointer + hourglass") cursor for a number
+    of seconds, or until the app does something UI-ish (eg, creating a
+    window, or fetching a message).  As this launcher doesn't do this
+    directly, that cursor remains even after the child process does these
+    things.  We avoid that by doing a simple post+get message.
+    See http://bugs.python.org/issue17290
+    */
+    MSG msg;
+
+    PostMessage(0, 0, 0, 0);
+    GetMessage(&msg, 0, 0, 0);
+#endif
+
+    debug(L"run_child: about to run '%ls' with '%ls'\n", executable, cmdline);
+    job = CreateJobObject(NULL, NULL);
+    ok = QueryInformationJobObject(job, JobObjectExtendedLimitInformation,
+                                   &info, sizeof(info), &rc);
+    if (!ok || (rc != sizeof(info)) || !job) {
+        winerror(GetLastError(), L"Job information querying failed");
+        return RC_CREATE_PROCESS;
+    }
+    info.BasicLimitInformation.LimitFlags |= JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE |
+                                             JOB_OBJECT_LIMIT_SILENT_BREAKAWAY_OK;
+    ok = SetInformationJobObject(job, JobObjectExtendedLimitInformation, &info,
+                                 sizeof(info));
+    if (!ok) {
+        winerror(GetLastError(), L"Job information setting failed");
+        return RC_CREATE_PROCESS;
+    }
+    memset(&si, 0, sizeof(si));
+    GetStartupInfoW(&si);
+    ok = safe_duplicate_handle(GetStdHandle(STD_INPUT_HANDLE), &si.hStdInput, L"stdin");
+    if (!ok) {
+        return RC_NO_STD_HANDLES;
+    }
+    ok = safe_duplicate_handle(GetStdHandle(STD_OUTPUT_HANDLE), &si.hStdOutput, L"stdout");
+    if (!ok) {
+        return RC_NO_STD_HANDLES;
+    }
+    ok = safe_duplicate_handle(GetStdHandle(STD_ERROR_HANDLE), &si.hStdError, L"stderr");
+    if (!ok) {
+        return RC_NO_STD_HANDLES;
+    }
+
+    ok = SetConsoleCtrlHandler(ctrl_c_handler, TRUE);
+    if (!ok) {
+        winerror(GetLastError(), L"control handler setting failed");
+        return RC_CREATE_PROCESS;
+    }
+
+    si.dwFlags = STARTF_USESTDHANDLES;
+    ok = CreateProcessW(executable, cmdline, NULL, NULL, TRUE,
+                        0, NULL, NULL, &si, &pi);
+    if (!ok) {
+        winerror(GetLastError(), L"Unable to create process using '%ls'", cmdline);
+        return RC_CREATE_PROCESS;
+    }
+    AssignProcessToJobObject(job, pi.hProcess);
+    CloseHandle(pi.hThread);
+    WaitForSingleObjectEx(pi.hProcess, INFINITE, FALSE);
+    ok = GetExitCodeProcess(pi.hProcess, &rc);
+    if (!ok) {
+        winerror(GetLastError(), L"Failed to get exit code of process");
+        return RC_CREATE_PROCESS;
+    }
+    debug(L"child process exit code: %d", rc);
+    return rc;
+}
+
+
+int
+process(int argc, wchar_t ** argv)
+{
+    int exitCode;
+    wchar_t pyvenvcfg_path[MAXLEN];
+    wchar_t home_path[MAXLEN];
+
+    if (isEnvVarSet(L"PYLAUNCHER_DEBUG")) {
+        setvbuf(stderr, (char *)NULL, _IONBF, 0);
+        log_fp = stderr;
+    }
+
+    exitCode = calculate_pyvenvcfg_path(pyvenvcfg_path, MAXLEN);
+    if (exitCode) return exitCode;
+
+    exitCode = read_home(pyvenvcfg_path, home_path, MAXLEN);
+    if (exitCode) return exitCode;
+
+    exitCode = locate_python(home_path, MAXLEN);
+    if (exitCode) return exitCode;
+
+    // We do not update argv[0] to point at the target runtime, and so we do not
+    // pass through our original argv[0] in an environment variable.
+    //exitCode = smuggle_path();
+    //if (exitCode) return exitCode;
+
+    exitCode = launch(home_path, GetCommandLineW());
+    return exitCode;
+}
+
+
+#if defined(_WINDOWS)
+
+int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
+                   LPWSTR lpstrCmd, int nShow)
+{
+    return process(__argc, __wargv);
+}
+
+#else
+
+int cdecl wmain(int argc, wchar_t ** argv)
+{
+    return process(argc, argv);
+}
+
+#endif