bpo-46566: Add new py.exe launcher implementation (GH-32062)

1 files changed, 2264 insertions, 0 deletions

diff --git a/PC/launcher2.c b/PC/launcher2.c
new file mode 100644
index 0000000..8735381
--- /dev/null
+++ b/PC/launcher2.c
@@ -0,0 +1,2264 @@
+/*
+ * Rewritten Python launcher for Windows
+ *
+ * This new rewrite properly handles PEP 514 and allows any registered Python
+ * runtime to be launched. It also enables auto-install of versions when they
+ * are requested but no installation can be found.
+ */
+
+#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>
+
+#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_BAD_VIRTUAL_PATH 102
+#define RC_NO_PYTHON        103
+#define RC_NO_MEMORY        104
+#define RC_NO_SCRIPT        105
+#define RC_NO_VENV_CFG      106
+#define RC_BAD_VENV_CFG     107
+#define RC_NO_COMMANDLINE   108
+#define RC_INTERNAL_ERROR   109
+#define RC_DUPLICATE_ITEM   110
+#define RC_INSTALLING       111
+#define RC_NO_PYTHON_AT_ALL 112
+
+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;
+        }
+        fputws(buffer, log_fp);
+        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": %s",
+                     win_message);
+    }
+
+#if !defined(_WINDOWS)
+    fwprintf(stderr, L"%s\n", message);
+#else
+    MessageBoxW(NULL, message, L"Python 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"%s\n", message);
+#else
+    MessageBoxW(NULL, message, L"Python Launcher is sorry to say ...",
+               MB_OK);
+#endif
+}
+
+
+typedef BOOL (*PIsWow64Process2)(HANDLE, USHORT*, USHORT*);
+
+
+USHORT
+_getNativeMachine()
+{
+    static USHORT _nativeMachine = IMAGE_FILE_MACHINE_UNKNOWN;
+    if (_nativeMachine == IMAGE_FILE_MACHINE_UNKNOWN) {
+        USHORT processMachine;
+        HMODULE kernel32 = GetModuleHandleW(L"kernel32.dll");
+        PIsWow64Process2 IsWow64Process2 = kernel32 ?
+            (PIsWow64Process2)GetProcAddress(kernel32, "IsWow64Process2") :
+            NULL;
+        if (!IsWow64Process2) {
+            BOOL wow64Process;
+            if (!IsWow64Process(NULL, &wow64Process)) {
+                winerror(0, L"Checking process type");
+            } else if (wow64Process) {
+                // We should always be a 32-bit executable, so if running
+                // under emulation, it must be a 64-bit host.
+                _nativeMachine = IMAGE_FILE_MACHINE_AMD64;
+            } else {
+                // Not running under emulation, and an old enough OS to not
+                // have IsWow64Process2, so assume it's x86.
+                _nativeMachine = IMAGE_FILE_MACHINE_I386;
+            }
+        } else if (!IsWow64Process2(NULL, &processMachine, &_nativeMachine)) {
+            winerror(0, L"Checking process type");
+        }
+    }
+    return _nativeMachine;
+}
+
+
+bool
+isAMD64Host()
+{
+    return _getNativeMachine() == IMAGE_FILE_MACHINE_AMD64;
+}
+
+
+bool
+isARM64Host()
+{
+    return _getNativeMachine() == IMAGE_FILE_MACHINE_ARM64;
+}
+
+
+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;
+}
+
+
+int
+_compare(const wchar_t *x, int xLen, const wchar_t *y, int yLen)
+{
+    // Empty strings sort first
+    if (xLen == 0) {
+        return yLen == 0 ? 0 : -1;
+    } else if (yLen == 0) {
+        return 1;
+    }
+    switch (CompareStringEx(
+        LOCALE_NAME_INVARIANT, NORM_IGNORECASE | SORT_DIGITSASNUMBERS,
+        x, xLen, y, yLen,
+        NULL, NULL, 0
+    )) {
+    case CSTR_LESS_THAN:
+        return -1;
+    case CSTR_EQUAL:
+        return 0;
+    case CSTR_GREATER_THAN:
+        return 1;
+    default:
+        winerror(0, L"Error comparing '%.*s' and '%.*s' (compare)", xLen, x, yLen, y);
+        return -1;
+    }
+}
+
+
+int
+_compareArgument(const wchar_t *x, int xLen, const wchar_t *y, int yLen)
+{
+    // Empty strings sort first
+    if (xLen == 0) {
+        return yLen == 0 ? 0 : -1;
+    } else if (yLen == 0) {
+        return 1;
+    }
+    switch (CompareStringEx(
+        LOCALE_NAME_INVARIANT, 0,
+        x, xLen, y, yLen,
+        NULL, NULL, 0
+    )) {
+    case CSTR_LESS_THAN:
+        return -1;
+    case CSTR_EQUAL:
+        return 0;
+    case CSTR_GREATER_THAN:
+        return 1;
+    default:
+        winerror(0, L"Error comparing '%.*s' and '%.*s' (compareArgument)", xLen, x, yLen, y);
+        return -1;
+    }
+}
+
+int
+_comparePath(const wchar_t *x, int xLen, const wchar_t *y, int yLen)
+{
+    // Empty strings sort first
+    if (xLen == 0) {
+        return yLen == 0 ? 0 : -1;
+    } else if (yLen == 0) {
+        return 1;
+    }
+    switch (CompareStringOrdinal(x, xLen, y, yLen, TRUE)) {
+    case CSTR_LESS_THAN:
+        return -1;
+    case CSTR_EQUAL:
+        return 0;
+    case CSTR_GREATER_THAN:
+        return 1;
+    default:
+        winerror(0, L"Error comparing '%.*s' and '%.*s' (comparePath)", xLen, x, yLen, y);
+        return -1;
+    }
+}
+
+
+bool
+_startsWith(const wchar_t *x, int xLen, const wchar_t *y, int yLen)
+{
+    yLen = yLen < 0 ? (int)wcsnlen_s(y, MAXLEN) : yLen;
+    xLen = xLen < 0 ? (int)wcsnlen_s(x, MAXLEN) : xLen;
+    return xLen >= yLen && 0 == _compare(x, yLen, y, yLen);
+}
+
+
+bool
+_startsWithArgument(const wchar_t *x, int xLen, const wchar_t *y, int yLen)
+{
+    yLen = yLen < 0 ? (int)wcsnlen_s(y, MAXLEN) : yLen;
+    xLen = xLen < 0 ? (int)wcsnlen_s(x, MAXLEN) : xLen;
+    return xLen >= yLen && 0 == _compareArgument(x, yLen, y, yLen);
+}
+
+
+/******************************************************************************\
+ ***                               HELP TEXT                                ***
+\******************************************************************************/
+
+
+int
+showHelpText(wchar_t ** argv)
+{
+    // The help text is stored in launcher-usage.txt, which is compiled into
+    // the launcher and loaded at runtime if needed.
+    //
+    // The file must be UTF-8. There are two substitutions:
+    //  %ls - PY_VERSION (as wchar_t*)
+    //  %ls - argv[0] (as wchar_t*)
+    HRSRC res = FindResourceExW(NULL, L"USAGE", MAKEINTRESOURCE(1), MAKELANGID(LANG_NEUTRAL, SUBLANG_NEUTRAL));
+    HGLOBAL resData = res ? LoadResource(NULL, res) : NULL;
+    const char *usage = resData ? (const char*)LockResource(resData) : NULL;
+    if (usage == NULL) {
+        winerror(0, L"Unable to load usage text");
+        return RC_INTERNAL_ERROR;
+    }
+
+    DWORD cbData = SizeofResource(NULL, res);
+    DWORD cchUsage = MultiByteToWideChar(CP_UTF8, 0, usage, cbData, NULL, 0);
+    if (!cchUsage) {
+        winerror(0, L"Unable to preprocess usage text");
+        return RC_INTERNAL_ERROR;
+    }
+
+    cchUsage += 1;
+    wchar_t *wUsage = (wchar_t*)malloc(cchUsage * sizeof(wchar_t));
+    cchUsage = MultiByteToWideChar(CP_UTF8, 0, usage, cbData, wUsage, cchUsage);
+    if (!cchUsage) {
+        winerror(0, L"Unable to preprocess usage text");
+        free((void *)wUsage);
+        return RC_INTERNAL_ERROR;
+    }
+    // Ensure null termination
+    wUsage[cchUsage] = L'\0';
+
+    fwprintf(stdout, wUsage, (L"" PY_VERSION), argv[0]);
+    fflush(stdout);
+
+    free((void *)wUsage);
+
+    return 0;
+}
+
+
+/******************************************************************************\
+ ***                              SEARCH INFO                               ***
+\******************************************************************************/
+
+
+struct _SearchInfoBuffer {
+    struct _SearchInfoBuffer *next;
+    wchar_t buffer[0];
+};
+
+
+typedef struct {
+    // the original string, managed by the OS
+    const wchar_t *originalCmdLine;
+    // pointer into the cmdline to mark what we've consumed
+    const wchar_t *restOfCmdLine;
+    // if known/discovered, the full executable path of our runtime
+    const wchar_t *executablePath;
+    // pointer and length into cmdline for the file to check for a
+    // shebang line, if any. Length can be -1 if the string is null
+    // terminated.
+    const wchar_t *scriptFile;
+    int scriptFileLength;
+    // pointer and length into cmdline or a static string with the
+    // name of the target executable. Length can be -1 if the string
+    // is null terminated.
+    const wchar_t *executable;
+    int executableLength;
+    // pointer and length into a string with additional interpreter
+    // arguments to include before restOfCmdLine. Length can be -1 if
+    // the string is null terminated.
+    const wchar_t *executableArgs;
+    int executableArgsLength;
+    // pointer and length into cmdline or a static string with the
+    // company name for PEP 514 lookup. Length can be -1 if the string
+    // is null terminated.
+    const wchar_t *company;
+    int companyLength;
+    // pointer and length into cmdline or a static string with the
+    // tag for PEP 514 lookup. Length can be -1 if the string is
+    // null terminated.
+    const wchar_t *tag;
+    int tagLength;
+    // if true, treats 'tag' as a non-PEP 514 filter
+    bool oldStyleTag;
+    // if true, we had an old-style tag with '-64' suffix, and so do not
+    // want to match tags like '3.x-32'
+    bool exclude32Bit;
+    // if true, we had an old-style tag with '-32' suffix, and so *only*
+    // want to match tags like '3.x-32'
+    bool only32Bit;
+    // if true, allow PEP 514 lookup to override 'executable'
+    bool allowExecutableOverride;
+    // if true, allow a nearby pyvenv.cfg to locate the executable
+    bool allowPyvenvCfg;
+    // if true, allow defaults (env/py.ini) to clarify/override tags
+    bool allowDefaults;
+    // if true, prefer windowed (console-less) executable
+    bool windowed;
+    // if true, only list detected runtimes without launching
+    bool list;
+    // if true, only list detected runtimes with paths without launching
+    bool listPaths;
+    // if true, display help message before contiuning
+    bool help;
+    // dynamically allocated buffers to free later
+    struct _SearchInfoBuffer *_buffer;
+} SearchInfo;
+
+
+wchar_t *
+allocSearchInfoBuffer(SearchInfo *search, int wcharCount)
+{
+    struct _SearchInfoBuffer *buffer = (struct _SearchInfoBuffer*)malloc(
+        sizeof(struct _SearchInfoBuffer) +
+        wcharCount * sizeof(wchar_t)
+    );
+    if (!buffer) {
+        return NULL;
+    }
+    buffer->next = search->_buffer;
+    search->_buffer = buffer;
+    return buffer->buffer;
+}
+
+
+void
+freeSearchInfo(SearchInfo *search)
+{
+    struct _SearchInfoBuffer *b = search->_buffer;
+    search->_buffer = NULL;
+    while (b) {
+        struct _SearchInfoBuffer *nextB = b->next;
+        free((void *)b);
+        b = nextB;
+    }
+}
+
+
+void
+_debugStringAndLength(const wchar_t *s, int len, const wchar_t *name)
+{
+    if (!s) {
+        debug(L"%s: (null)\n", name);
+    } else if (len == 0) {
+        debug(L"%s: (empty)\n", name);
+    } else if (len < 0) {
+        debug(L"%s: %s\n", name, s);
+    } else {
+        debug(L"%s: %.*ls\n", name, len, s);
+    }
+}
+
+
+void
+dumpSearchInfo(SearchInfo *search)
+{
+    if (!log_fp) {
+        return;
+    }
+
+#define DEBUGNAME(s) L"SearchInfo." ## s
+#define DEBUG(s) debug(DEBUGNAME(#s) L": %s\n", (search->s) ? (search->s) : L"(null)")
+#define DEBUG_2(s, sl) _debugStringAndLength((search->s), (search->sl), DEBUGNAME(#s))
+#define DEBUG_BOOL(s) debug(DEBUGNAME(#s) L": %s\n", (search->s) ? L"True" : L"False")
+    DEBUG(originalCmdLine);
+    DEBUG(restOfCmdLine);
+    DEBUG(executablePath);
+    DEBUG_2(scriptFile, scriptFileLength);
+    DEBUG_2(executable, executableLength);
+    DEBUG_2(executableArgs, executableArgsLength);
+    DEBUG_2(company, companyLength);
+    DEBUG_2(tag, tagLength);
+    DEBUG_BOOL(oldStyleTag);
+    DEBUG_BOOL(exclude32Bit);
+    DEBUG_BOOL(only32Bit);
+    DEBUG_BOOL(allowDefaults);
+    DEBUG_BOOL(allowExecutableOverride);
+    DEBUG_BOOL(windowed);
+    DEBUG_BOOL(list);
+    DEBUG_BOOL(listPaths);
+    DEBUG_BOOL(help);
+#undef DEBUG_BOOL
+#undef DEBUG_2
+#undef DEBUG
+#undef DEBUGNAME
+}
+
+
+int
+findArgumentLength(const wchar_t *buffer, int bufferLength)
+{
+    if (bufferLength < 0) {
+        bufferLength = (int)wcsnlen_s(buffer, MAXLEN);
+    }
+    if (bufferLength == 0) {
+        return 0;
+    }
+    const wchar_t *end;
+    int i;
+
+    if (buffer[0] != L'"') {
+        end = wcschr(buffer, L' ');
+        if (!end) {
+            return bufferLength;
+        }
+        i = (int)(end - buffer);
+        return i < bufferLength ? i : bufferLength;
+    }
+
+    i = 0;
+    while (i < bufferLength) {
+        end = wcschr(&buffer[i + 1], L'"');
+        if (!end) {
+            return bufferLength;
+        }
+
+        i = (int)(end - buffer);
+        if (i >= bufferLength) {
+            return bufferLength;
+        }
+
+        int j = i;
+        while (j > 1 && buffer[--j] == L'\\') {
+            if (j > 0 && buffer[--j] == L'\\') {
+                // Even number, so back up and keep counting
+            } else {
+                // Odd number, so it's escaped and we want to keep searching
+                continue;
+            }
+        }
+
+        // Non-escaped quote with space after it - end of the argument!
+        if (i + 1 >= bufferLength || isspace(buffer[i + 1])) {
+            return i + 1;
+        }
+    }
+
+    return bufferLength;
+}
+
+
+const wchar_t *
+findArgumentEnd(const wchar_t *buffer, int bufferLength)
+{
+    return &buffer[findArgumentLength(buffer, bufferLength)];
+}
+
+
+/******************************************************************************\
+ ***                          COMMAND-LINE PARSING                          ***
+\******************************************************************************/
+
+
+int
+parseCommandLine(SearchInfo *search)
+{
+    if (!search || !search->originalCmdLine) {
+        return RC_NO_COMMANDLINE;
+    }
+
+    const wchar_t *tail = findArgumentEnd(search->originalCmdLine, -1);
+    const wchar_t *end = tail;
+    search->restOfCmdLine = tail;
+    while (--tail != search->originalCmdLine) {
+        if (*tail == L'.' && end == search->restOfCmdLine) {
+            end = tail;
+        } else if (*tail == L'\\' || *tail == L'/') {
+            ++tail;
+            break;
+        }
+    }
+    // Without special cases, we can now fill in the search struct
+    int tailLen = (int)(end ? (end - tail) : wcsnlen_s(tail, MAXLEN));
+    search->executableLength = -1;
+
+    // Our special cases are as follows
+#define MATCHES(s) (0 == _comparePath(tail, tailLen, (s), -1))
+#define STARTSWITH(s) _startsWith(tail, tailLen, (s), -1)
+    if (MATCHES(L"py")) {
+        search->executable = L"python.exe";
+        search->allowExecutableOverride = true;
+        search->allowDefaults = true;
+    } else if (MATCHES(L"pyw")) {
+        search->executable = L"pythonw.exe";
+        search->allowExecutableOverride = true;
+        search->allowDefaults = true;
+        search->windowed = true;
+    } else if (MATCHES(L"py_d")) {
+        search->executable = L"python_d.exe";
+        search->allowExecutableOverride = true;
+        search->allowDefaults = true;
+    } else if (MATCHES(L"pyw_d")) {
+        search->executable = L"pythonw_d.exe";
+        search->allowExecutableOverride = true;
+        search->allowDefaults = true;
+        search->windowed = true;
+    } else if (STARTSWITH(L"python3")) {
+        search->executable = L"python.exe";
+        search->tag = &tail[6];
+        search->tagLength = tailLen - 6;
+        search->allowExecutableOverride = true;
+        search->oldStyleTag = true;
+        search->allowPyvenvCfg = true;
+    } else if (STARTSWITH(L"pythonw3")) {
+        search->executable = L"pythonw.exe";
+        search->tag = &tail[7];
+        search->tagLength = tailLen - 7;
+        search->allowExecutableOverride = true;
+        search->oldStyleTag = true;
+        search->allowPyvenvCfg = true;
+        search->windowed = true;
+    } else {
+        search->executable = tail;
+        search->executableLength = tailLen;
+        search->allowPyvenvCfg = true;
+    }
+#undef STARTSWITH
+#undef MATCHES
+
+    // First argument might be one of our options. If so, consume it,
+    // update flags and then set restOfCmdLine.
+    const wchar_t *arg = search->restOfCmdLine;
+    while(*arg && isspace(*arg)) { ++arg; }
+#define MATCHES(s) (0 == _compareArgument(arg, argLen, (s), -1))
+#define STARTSWITH(s) _startsWithArgument(arg, argLen, (s), -1)
+    if (*arg && *arg == L'-' && *++arg) {
+        tail = arg;
+        while (*tail && !isspace(*tail)) { ++tail; }
+        int argLen = (int)(tail - arg);
+        if (argLen > 0) {
+            if (STARTSWITH(L"2") || STARTSWITH(L"3")) {
+                // All arguments starting with 2 or 3 are assumed to be version tags
+                search->tag = arg;
+                search->tagLength = argLen;
+                search->oldStyleTag = true;
+                search->restOfCmdLine = tail;
+                // If the tag ends with -64, we want to exclude 32-bit runtimes
+                // (If the tag ends with -32, it will be filtered later)
+                if (argLen > 3) {
+                    if (0 == _compareArgument(&arg[argLen - 3], 3, L"-64", 3)) {
+                        search->tagLength -= 3;
+                        search->exclude32Bit = true;
+                    } else if (0 == _compareArgument(&arg[argLen - 3], 3, L"-32", 3)) {
+                        search->tagLength -= 3;
+                        search->only32Bit = true;
+                    }
+                }
+            } else if (STARTSWITH(L"V:") || STARTSWITH(L"-version:")) {
+                // Arguments starting with 'V:' specify company and/or tag
+                const wchar_t *argStart = wcschr(arg, L':') + 1;
+                const wchar_t *tagStart = wcschr(argStart, L'/') ;
+                if (tagStart) {
+                    search->company = argStart;
+                    search->companyLength = (int)(tagStart - argStart);
+                    search->tag = tagStart + 1;
+                } else {
+                    search->tag = argStart;
+                }
+                search->tagLength = (int)(tail - search->tag);
+                search->restOfCmdLine = tail;
+            } else if (MATCHES(L"0") || MATCHES(L"-list")) {
+                search->list = true;
+                search->restOfCmdLine = tail;
+            } else if (MATCHES(L"0p") || MATCHES(L"-list-paths")) {
+                search->listPaths = true;
+                search->restOfCmdLine = tail;
+            } else if (MATCHES(L"h") || MATCHES(L"-help")) {
+                search->help = true;
+                // Do not update restOfCmdLine so that we trigger the help
+                // message from whichever interpreter we select
+            }
+        }
+    }
+#undef STARTSWITH
+#undef MATCHES
+
+    // Might have a script filename. If it looks like a filename, add
+    // it to the SearchInfo struct for later reference.
+    arg = search->restOfCmdLine;
+    while(*arg && isspace(*arg)) { ++arg; }
+    if (*arg && *arg != L'-') {
+        search->scriptFile = arg;
+        if (*arg == L'"') {
+            ++search->scriptFile;
+            while (*++arg && *arg != L'"') { }
+        } else {
+            while (*arg && !isspace(*arg)) { ++arg; }
+        }
+        search->scriptFileLength = (int)(arg - search->scriptFile);
+    }
+
+    return 0;
+}
+
+
+int
+_decodeShebang(SearchInfo *search, const char *buffer, int bufferLength, bool onlyUtf8, wchar_t **decoded, int *decodedLength)
+{
+    DWORD cp = CP_UTF8;
+    int wideLen = MultiByteToWideChar(cp, MB_ERR_INVALID_CHARS, buffer, bufferLength, NULL, 0);
+    if (!wideLen) {
+        cp = CP_ACP;
+        wideLen = MultiByteToWideChar(cp, MB_ERR_INVALID_CHARS, buffer, bufferLength, NULL, 0);
+        if (!wideLen) {
+            debug(L"# Failed to decode shebang line (0x%08X)\n", GetLastError());
+            return RC_BAD_VIRTUAL_PATH;
+        }
+    }
+    wchar_t *b = allocSearchInfoBuffer(search, wideLen + 1);
+    if (!b) {
+        return RC_NO_MEMORY;
+    }
+    wideLen = MultiByteToWideChar(cp, 0, buffer, bufferLength, b, wideLen + 1);
+    if (!wideLen) {
+        debug(L"# Failed to decode shebang line (0x%08X)\n", GetLastError());
+        return RC_BAD_VIRTUAL_PATH;
+    }
+    b[wideLen] = L'\0';
+    *decoded = b;
+    *decodedLength = wideLen;
+    return 0;
+}
+
+
+bool
+_shebangStartsWith(const wchar_t *buffer, int bufferLength, const wchar_t *prefix, const wchar_t **rest)
+{
+    int prefixLength = (int)wcsnlen_s(prefix, MAXLEN);
+    if (bufferLength < prefixLength) {
+        return false;
+    }
+    if (rest) {
+        *rest = &buffer[prefixLength];
+    }
+    return _startsWithArgument(buffer, bufferLength, prefix, prefixLength);
+}
+
+
+int
+_readIni(const wchar_t *section, const wchar_t *settingName, wchar_t *buffer, int bufferLength)
+{
+    wchar_t iniPath[MAXLEN];
+    int n;
+    if (SUCCEEDED(SHGetFolderPathW(NULL, CSIDL_LOCAL_APPDATA, NULL, 0, iniPath)) &&
+        join(iniPath, MAXLEN, L"py.ini")) {
+        debug(L"# Reading from %s for %s/%s\n", iniPath, section, settingName);
+        n = GetPrivateProfileStringW(section, settingName, NULL, buffer, bufferLength, iniPath);
+        if (n) {
+            debug(L"# Found %s in %s\n", settingName, iniPath);
+            return true;
+        } else if (GetLastError() == ERROR_FILE_NOT_FOUND) {
+            debug(L"# Did not find file %s\n", iniPath);
+        } else {
+            winerror(0, L"Failed to read from %s\n", iniPath);
+        }
+    }
+    if (GetModuleFileNameW(NULL, iniPath, MAXLEN) &&
+        SUCCEEDED(PathCchRemoveFileSpec(iniPath, MAXLEN)) &&
+        join(iniPath, MAXLEN, L"py.ini")) {
+        debug(L"# Reading from %s for %s/%s\n", iniPath, section, settingName);
+        n = GetPrivateProfileStringW(section, settingName, NULL, buffer, MAXLEN, iniPath);
+        if (n) {
+            debug(L"# Found %s in %s\n", settingName, iniPath);
+            return n;
+        } else if (GetLastError() == ERROR_FILE_NOT_FOUND) {
+            debug(L"# Did not find file %s\n", iniPath);
+        } else {
+            winerror(0, L"Failed to read from %s\n", iniPath);
+        }
+    }
+    return 0;
+}
+
+
+bool
+_findCommand(SearchInfo *search, const wchar_t *command, int commandLength)
+{
+    wchar_t commandBuffer[MAXLEN];
+    wchar_t buffer[MAXLEN];
+    wcsncpy_s(commandBuffer, MAXLEN, command, commandLength);
+    int n = _readIni(L"commands", commandBuffer, buffer, MAXLEN);
+    if (!n) {
+        return false;
+    }
+    wchar_t *path = allocSearchInfoBuffer(search, n + 1);
+    if (!path) {
+        return false;
+    }
+    wcscpy_s(path, n + 1, buffer);
+    search->executablePath = path;
+    return true;
+}
+
+
+int
+checkShebang(SearchInfo *search)
+{
+    // Do not check shebang if a tag was provided or if no script file
+    // was found on the command line.
+    if (search->tag || !search->scriptFile) {
+        return 0;
+    }
+
+    if (search->scriptFileLength < 0) {
+        search->scriptFileLength = (int)wcsnlen_s(search->scriptFile, MAXLEN);
+    }
+
+    wchar_t *scriptFile = (wchar_t*)malloc(sizeof(wchar_t) * (search->scriptFileLength + 1));
+    if (!scriptFile) {
+        return RC_NO_MEMORY;
+    }
+
+    wcsncpy_s(scriptFile, search->scriptFileLength + 1,
+              search->scriptFile, search->scriptFileLength);
+
+    HANDLE hFile = CreateFileW(scriptFile, GENERIC_READ,
+        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+        NULL, OPEN_EXISTING, 0, NULL);
+
+    if (hFile == INVALID_HANDLE_VALUE) {
+        debug(L"# Failed to open %s for shebang parsing (0x%08X)\n",
+              scriptFile, GetLastError());
+        free(scriptFile);
+        return 0;
+    }
+
+    DWORD bytesRead = 0;
+    char buffer[4096];
+    if (!ReadFile(hFile, buffer, sizeof(buffer), &bytesRead, NULL)) {
+        debug(L"# Failed to read %s for shebang parsing (0x%08X)\n",
+              scriptFile, GetLastError());
+        free(scriptFile);
+        return 0;
+    }
+
+    CloseHandle(hFile);
+    debug(L"# Read %d bytes from %s to find shebang line\n", bytesRead, scriptFile);
+    free(scriptFile);
+
+
+    char *b = buffer;
+    bool onlyUtf8 = false;
+    if (bytesRead > 3 && *b == 0xEF) {
+        if (*++b == 0xBB && *++b == 0xBF) {
+            // Allow a UTF-8 BOM
+            ++b;
+            bytesRead -= 3;
+            onlyUtf8 = true;
+        } else {
+            debug(L"# Invalid BOM in shebang line");
+            return 0;
+        }
+    }
+    if (bytesRead <= 2 || b[0] != '#' || b[1] != '!') {
+        // No shebang (#!) at start of line
+        debug(L"# No valid shebang line");
+        return 0;
+    }
+    ++b;
+    --bytesRead;
+    while (--bytesRead > 0 && isspace(*++b)) { }
+    char *start = b;
+    while (--bytesRead > 0 && *++b != '\r' && *b != '\n') { }
+    wchar_t *shebang;
+    int shebangLength;
+    int exitCode = _decodeShebang(search, start, (int)(b - start + 1), onlyUtf8, &shebang, &shebangLength);
+    if (exitCode) {
+        return exitCode;
+    }
+    debug(L"Shebang: %s\n", shebang);
+
+    // Handle some known, case-sensitive shebang templates
+    const wchar_t *command;
+    int commandLength;
+    static const wchar_t *shebangTemplates[] = {
+        L"/usr/bin/env ",
+        L"/usr/bin/",
+        L"/usr/local/bin/",
+        L"",
+        NULL
+    };
+    for (const wchar_t **tmpl = shebangTemplates; *tmpl; ++tmpl) {
+        if (_shebangStartsWith(shebang, shebangLength, *tmpl, &command)) {
+            commandLength = 0;
+            while (command[commandLength] && !isspace(command[commandLength])) {
+                commandLength += 1;
+            }
+            if (!commandLength) {
+            } else if (_findCommand(search, command, commandLength)) {
+                search->executableArgs = &command[commandLength];
+                search->executableArgsLength = shebangLength - commandLength;
+                debug(L"# Treating shebang command '%.*s' as %s\n",
+                    commandLength, command, search->executablePath);
+            } else if (_shebangStartsWith(command, commandLength, L"python", NULL)) {
+                search->tag = &command[6];
+                search->tagLength = commandLength - 6;
+                search->oldStyleTag = true;
+                search->executableArgs = &command[commandLength];
+                search->executableArgsLength = shebangLength - commandLength;
+                debug(L"# Treating shebang command '%.*s' as 'py -%.*s'\n",
+                    commandLength, command, search->tagLength, search->tag);
+            } else {
+                debug(L"# Found shebang command but could not execute it: %.*s\n",
+                    commandLength, command);
+            }
+            break;
+        }
+    }
+
+    return 0;
+}
+
+
+int
+checkDefaults(SearchInfo *search)
+{
+    if (!search->allowDefaults || search->list || search->listPaths) {
+        return 0;
+    }
+
+    wchar_t buffer[MAXLEN];
+    int n;
+
+    // If no tag was provided at all, look for an active virtual environment
+    if (!search->tag || !search->tagLength) {
+        n = GetEnvironmentVariableW(L"VIRTUAL_ENV", buffer, MAXLEN);
+        if (n && join(buffer, MAXLEN, L"Scripts") && join(buffer, MAXLEN, search->executable)) {
+            if (INVALID_FILE_ATTRIBUTES != GetFileAttributesW(buffer)) {
+                n = (int)wcsnlen_s(buffer, MAXLEN) + 1;
+                wchar_t *path = allocSearchInfoBuffer(search, n);
+                if (!path) {
+                    return RC_NO_MEMORY;
+                }
+                search->executablePath = path;
+                wcscpy_s(path, n, buffer);
+                return 0;
+            } else {
+                debug(L"Python executable %s missing from virtual env\n", buffer);
+            }
+        }
+    }
+
+    // Only resolve old-style (or absent) tags to defaults
+    if (search->tag && search->tagLength && !search->oldStyleTag) {
+        return 0;
+    }
+
+    // If tag is only a major version number, expand it from the environment
+    // or an ini file
+    const wchar_t *settingName = NULL;
+    if (!search->tag || !search->tagLength) {
+        settingName = L"py_python";
+    } else if (0 == wcsncmp(search->tag, L"3", search->tagLength)) {
+        settingName = L"py_python3";
+    } else if (0 == wcsncmp(search->tag, L"2", search->tagLength)) {
+        settingName = L"py_python2";
+    } else {
+        debug(L"# Cannot select defaults for tag '%.*s'\n", search->tagLength, search->tag);
+        return 0;
+    }
+
+    // First, try to read an environment variable
+    n = GetEnvironmentVariableW(settingName, buffer, MAXLEN);
+
+    // If none found, check in our two .ini files instead
+    if (!n) {
+        n = _readIni(L"defaults", settingName, buffer, MAXLEN);
+    }
+
+    if (n) {
+        wchar_t *tag = allocSearchInfoBuffer(search, n + 1);
+        if (!tag) {
+            return RC_NO_MEMORY;
+        }
+        wcscpy_s(tag, n + 1, buffer);
+        wchar_t *slash = wcschr(tag, L'/');
+        if (!slash) {
+            search->tag = tag;
+            search->tagLength = n;
+        } else {
+            search->company = tag;
+            search->companyLength = (int)(slash - tag);
+            search->tag = slash + 1;
+            search->tagLength = n - (search->companyLength + 1);
+            search->oldStyleTag = false;
+        }
+    }
+
+    return 0;
+}
+
+/******************************************************************************\
+ ***                          ENVIRONMENT SEARCH                            ***
+\******************************************************************************/
+
+typedef struct EnvironmentInfo {
+    /* We use a binary tree and sort on insert */
+    struct EnvironmentInfo *prev;
+    struct EnvironmentInfo *next;
+    /* parent is only used when constructing */
+    struct EnvironmentInfo *parent;
+    const wchar_t *company;
+    const wchar_t *tag;
+    int internalSortKey;
+    const wchar_t *installDir;
+    const wchar_t *executablePath;
+    const wchar_t *executableArgs;
+    const wchar_t *architecture;
+    const wchar_t *displayName;
+} EnvironmentInfo;
+
+
+int
+copyWstr(const wchar_t **dest, const wchar_t *src)
+{
+    if (!dest) {
+        return RC_NO_MEMORY;
+    }
+    if (!src) {
+        *dest = NULL;
+        return 0;
+    }
+    size_t n = wcsnlen_s(src, MAXLEN - 1) + 1;
+    wchar_t *buffer = (wchar_t*)malloc(n * sizeof(wchar_t));
+    if (!buffer) {
+        return RC_NO_MEMORY;
+    }
+    wcsncpy_s(buffer, n, src, n - 1);
+    *dest = (const wchar_t*)buffer;
+    return 0;
+}
+
+
+EnvironmentInfo *
+newEnvironmentInfo(const wchar_t *company, const wchar_t *tag)
+{
+    EnvironmentInfo *env = (EnvironmentInfo *)malloc(sizeof(EnvironmentInfo));
+    if (!env) {
+        return NULL;
+    }
+    memset(env, 0, sizeof(EnvironmentInfo));
+    int exitCode = copyWstr(&env->company, company);
+    if (exitCode) {
+        free((void *)env);
+        return NULL;
+    }
+    exitCode = copyWstr(&env->tag, tag);
+    if (exitCode) {
+        free((void *)env->company);
+        free((void *)env);
+        return NULL;
+    }
+    return env;
+}
+
+
+void
+freeEnvironmentInfo(EnvironmentInfo *env)
+{
+    if (env) {
+        free((void *)env->company);
+        free((void *)env->tag);
+        free((void *)env->installDir);
+        free((void *)env->executablePath);
+        free((void *)env->executableArgs);
+        free((void *)env->displayName);
+        freeEnvironmentInfo(env->prev);
+        env->prev = NULL;
+        freeEnvironmentInfo(env->next);
+        env->next = NULL;
+        free((void *)env);
+    }
+}
+
+
+/* Specific string comparisons for sorting the tree */
+
+int
+_compareCompany(const wchar_t *x, const wchar_t *y)
+{
+    bool coreX = 0 == _compare(x, -1, L"PythonCore", -1);
+    bool coreY = 0 == _compare(y, -1, L"PythonCore", -1);
+    if (coreX) {
+        return coreY ? 0 : -1;
+    } else if (coreY) {
+        return 1;
+    }
+    return _compare(x, -1, y, -1);
+}
+
+
+int
+_compareTag(const wchar_t *x, const wchar_t *y)
+{
+    // Compare up to the first dash. If not equal, that's our sort order
+    const wchar_t *xDash = wcschr(x, L'-');
+    const wchar_t *yDash = wcschr(y, L'-');
+    int xToDash = xDash ? (int)(xDash - x) : -1;
+    int yToDash = yDash ? (int)(yDash - y) : -1;
+    int r = _compare(x, xToDash, y, yToDash);
+    if (r) {
+        return r;
+    }
+    // If we're equal up to the first dash, we want to sort one with
+    // no dash *after* one with a dash. Otherwise, a reversed compare.
+    // This works out because environments are sorted in descending tag
+    // order, so that higher versions (probably) come first.
+    // For PythonCore, our "X.Y" structure ensures that higher versions
+    // come first. Everyone else will just have to deal with it.
+    if (xDash && yDash) {
+        return _compare(yDash, -1, xDash, -1);
+    } else if (xDash) {
+        return -1;
+    } else if (yDash) {
+        return 1;
+    }
+    return 0;
+}
+
+
+int
+addEnvironmentInfo(EnvironmentInfo **root, EnvironmentInfo *node)
+{
+    EnvironmentInfo *r = *root;
+    if (!r) {
+        *root = node;
+        node->parent = NULL;
+        return 0;
+    }
+    // Sort by company name
+    switch (_compareCompany(node->company, r->company)) {
+    case -1:
+        return addEnvironmentInfo(&r->prev, node);
+    case 1:
+        return addEnvironmentInfo(&r->next, node);
+    case 0:
+        break;
+    }
+    // Then by tag (descending)
+    switch (_compareTag(node->tag, r->tag)) {
+    case -1:
+        return addEnvironmentInfo(&r->next, node);
+    case 1:
+        return addEnvironmentInfo(&r->prev, node);
+    case 0:
+        break;
+    }
+    // Then keep the one with the lowest internal sort key
+    if (r->internalSortKey < node->internalSortKey) {
+        // Replace the current node
+        node->parent = r->parent;
+        if (node->parent) {
+            if (node->parent->prev == r) {
+                node->parent->prev = node;
+            } else if (node->parent->next == r) {
+                node->parent->next = node;
+            } else {
+                debug(L"# Inconsistent parent value in tree\n");
+                freeEnvironmentInfo(node);
+                return RC_INTERNAL_ERROR;
+            }
+        }
+        node->next = r->next;
+        node->prev = r->prev;
+    } else {
+        debug(L"# not adding %s/%s/%i to tree\n", node->company, node->tag, node->internalSortKey);
+        freeEnvironmentInfo(node);
+        return RC_DUPLICATE_ITEM;
+    }
+    return 0;
+}
+
+
+/******************************************************************************\
+ ***                            REGISTRY SEARCH                             ***
+\******************************************************************************/
+
+
+int
+_registryReadString(const wchar_t **dest, HKEY root, const wchar_t *subkey, const wchar_t *value)
+{
+    // Note that this is bytes (hence 'cb'), not characters ('cch')
+    DWORD cbData = 0;
+    DWORD flags = RRF_RT_REG_SZ | RRF_RT_REG_EXPAND_SZ;
+
+    if (ERROR_SUCCESS != RegGetValueW(root, subkey, value, flags, NULL, NULL, &cbData)) {
+        return 0;
+    }
+
+    wchar_t *buffer = (wchar_t*)malloc(cbData);
+    if (!buffer) {
+        return RC_NO_MEMORY;
+    }
+
+    if (ERROR_SUCCESS == RegGetValueW(root, subkey, value, flags, NULL, buffer, &cbData)) {
+        *dest = buffer;
+    } else {
+        free((void *)buffer);
+    }
+    return 0;
+}
+
+
+int
+_combineWithInstallDir(const wchar_t **dest, const wchar_t *installDir, const wchar_t *fragment, int fragmentLength)
+{
+    wchar_t buffer[MAXLEN];
+    wchar_t fragmentBuffer[MAXLEN];
+    if (wcsncpy_s(fragmentBuffer, MAXLEN, fragment, fragmentLength)) {
+        return RC_NO_MEMORY;
+    }
+
+    if (FAILED(PathCchCombineEx(buffer, MAXLEN, installDir, fragmentBuffer, PATHCCH_ALLOW_LONG_PATHS))) {
+        return RC_NO_MEMORY;
+    }
+
+    return copyWstr(dest, buffer);
+}
+
+
+int
+_registryReadEnvironment(const SearchInfo *search, HKEY root, EnvironmentInfo *env, const wchar_t *fallbackArch)
+{
+    int exitCode = _registryReadString(&env->installDir, root, L"InstallPath", NULL);
+    if (exitCode) {
+        return exitCode;
+    }
+    if (!env->installDir) {
+        return RC_NO_PYTHON;
+    }
+
+    // If pythonw.exe requested, check specific value
+    if (search->windowed) {
+        exitCode = _registryReadString(&env->executablePath, root, L"InstallPath", L"WindowedExecutablePath");
+        if (!exitCode && env->executablePath) {
+            exitCode = _registryReadString(&env->executableArgs, root, L"InstallPath", L"WindowedExecutableArguments");
+        }
+    }
+    if (exitCode) {
+        return exitCode;
+    }
+
+    // Missing windowed path or non-windowed request means we use ExecutablePath
+    if (!env->executablePath) {
+        exitCode = _registryReadString(&env->executablePath, root, L"InstallPath", L"ExecutablePath");
+        if (!exitCode && env->executablePath) {
+            exitCode = _registryReadString(&env->executableArgs, root, L"InstallPath", L"ExecutableArguments");
+        }
+    }
+    if (exitCode) {
+        return exitCode;
+    }
+
+    exitCode = _registryReadString(&env->architecture, root, NULL, L"SysArchitecture");
+    if (exitCode) {
+        return exitCode;
+    }
+
+    exitCode = _registryReadString(&env->displayName, root, NULL, L"DisplayName");
+    if (exitCode) {
+        return exitCode;
+    }
+
+    // Only PythonCore entries will infer executablePath from installDir and architecture from the binary
+    if (0 == _compare(env->company, -1, L"PythonCore", -1)) {
+        if (!env->executablePath) {
+            exitCode = _combineWithInstallDir(
+                &env->executablePath,
+                env->installDir,
+                search->executable,
+                search->executableLength
+            );
+            if (exitCode) {
+                return exitCode;
+            }
+        }
+        if (!env->architecture && env->executablePath && fallbackArch) {
+            copyWstr(&env->architecture, fallbackArch);
+        }
+    }
+
+    if (!env->executablePath) {
+        debug(L"# %s/%s has no executable path\n", env->company, env->tag);
+        return RC_NO_PYTHON;
+    }
+
+    return 0;
+}
+
+int
+_registrySearchTags(const SearchInfo *search, EnvironmentInfo **result, HKEY root, int sortKey, const wchar_t *company, const wchar_t *fallbackArch)
+{
+    wchar_t buffer[256];
+    int err = 0;
+    int exitCode = 0;
+    for (int i = 0; exitCode == 0; ++i) {
+        DWORD cchBuffer = sizeof(buffer) / sizeof(buffer[0]);
+        err = RegEnumKeyExW(root, i, buffer, &cchBuffer, NULL, NULL, NULL, NULL);
+        if (err) {
+            if (err != ERROR_NO_MORE_ITEMS) {
+                winerror(0, L"Failed to read installs (tags) from the registry");
+            }
+            break;
+        }
+        HKEY subkey;
+        if (ERROR_SUCCESS == RegOpenKeyExW(root, buffer, 0, KEY_READ, &subkey)) {
+            EnvironmentInfo *env = newEnvironmentInfo(company, buffer);
+            env->internalSortKey = sortKey;
+            exitCode = _registryReadEnvironment(search, subkey, env, fallbackArch);
+            RegCloseKey(subkey);
+            if (exitCode == RC_NO_PYTHON) {
+                freeEnvironmentInfo(env);
+                exitCode = 0;
+            } else if (!exitCode) {
+                exitCode = addEnvironmentInfo(result, env);
+                if (exitCode == RC_DUPLICATE_ITEM) {
+                    exitCode = 0;
+                } else if (exitCode) {
+                    freeEnvironmentInfo(env);
+                }
+            }
+        }
+    }
+    return exitCode;
+}
+
+
+int
+registrySearch(const SearchInfo *search, EnvironmentInfo **result, HKEY root, int sortKey, const wchar_t *fallbackArch)
+{
+    wchar_t buffer[256];
+    int err = 0;
+    int exitCode = 0;
+    for (int i = 0; exitCode == 0; ++i) {
+        DWORD cchBuffer = sizeof(buffer) / sizeof(buffer[0]);
+        err = RegEnumKeyExW(root, i, buffer, &cchBuffer, NULL, NULL, NULL, NULL);
+        if (err) {
+            if (err != ERROR_NO_MORE_ITEMS) {
+                winerror(0, L"Failed to read distributors (company) from the registry");
+            }
+            break;
+        }
+        HKEY subkey;
+        if (ERROR_SUCCESS == RegOpenKeyExW(root, buffer, 0, KEY_READ, &subkey)) {
+            exitCode = _registrySearchTags(search, result, subkey, sortKey, buffer, fallbackArch);
+            RegCloseKey(subkey);
+        }
+    }
+    return exitCode;
+}
+
+
+/******************************************************************************\
+ ***                            APP PACKAGE SEARCH                          ***
+\******************************************************************************/
+
+int
+appxSearch(const SearchInfo *search, EnvironmentInfo **result, const wchar_t *packageFamilyName, const wchar_t *tag, int sortKey)
+{
+    wchar_t realTag[32];
+    wchar_t buffer[MAXLEN];
+    const wchar_t *exeName = search->executable;
+    if (!exeName || search->allowExecutableOverride) {
+        exeName = search->windowed ? L"pythonw.exe" : L"python.exe";
+    }
+
+    if (FAILED(SHGetFolderPathW(NULL, CSIDL_LOCAL_APPDATA, NULL, 0, buffer)) ||
+        !join(buffer, MAXLEN, L"Microsoft\\WindowsApps") ||
+        !join(buffer, MAXLEN, packageFamilyName) ||
+        !join(buffer, MAXLEN, exeName)) {
+        return RC_INTERNAL_ERROR;
+    }
+
+    if (INVALID_FILE_ATTRIBUTES == GetFileAttributesW(buffer)) {
+        return RC_NO_PYTHON;
+    }
+
+    // Assume packages are native architecture, which means we need to append
+    // the '-arm64' on ARM64 host.
+    wcscpy_s(realTag, 32, tag);
+    if (isARM64Host()) {
+        wcscat_s(realTag, 32, L"-arm64");
+    }
+
+    EnvironmentInfo *env = newEnvironmentInfo(L"PythonCore", realTag);
+    if (!env) {
+        return RC_NO_MEMORY;
+    }
+    env->internalSortKey = sortKey;
+    if (isAMD64Host()) {
+        copyWstr(&env->architecture, L"64bit");
+    } else if (isARM64Host()) {
+        copyWstr(&env->architecture, L"ARM64");
+    }
+
+    copyWstr(&env->executablePath, buffer);
+
+    if (swprintf_s(buffer, MAXLEN, L"Python %s (Store)", tag)) {
+        copyWstr(&env->displayName, buffer);
+    }
+
+    int exitCode = addEnvironmentInfo(result, env);
+    if (exitCode == RC_DUPLICATE_ITEM) {
+        exitCode = 0;
+    } else if (exitCode) {
+        freeEnvironmentInfo(env);
+    }
+
+
+    return exitCode;
+}
+
+
+/******************************************************************************\
+ ***                           COLLECT ENVIRONMENTS                         ***
+\******************************************************************************/
+
+
+struct RegistrySearchInfo {
+    // Registry subkey to search
+    const wchar_t *subkey;
+    // Registry hive to search
+    HKEY hive;
+    // Flags to use when opening the subkey
+    DWORD flags;
+    // Internal sort key to select between "identical" environments discovered
+    // through different methods
+    int sortKey;
+    // Fallback value to assume for PythonCore entries missing a SysArchitecture value
+    const wchar_t *fallbackArch;
+};
+
+
+struct RegistrySearchInfo REGISTRY_SEARCH[] = {
+    {
+        L"Software\\Python",
+        HKEY_CURRENT_USER,
+        KEY_READ,
+        1,
+        NULL
+    },
+    {
+        L"Software\\Python",
+        HKEY_LOCAL_MACHINE,
+        KEY_READ | KEY_WOW64_64KEY,
+        3,
+        L"64bit"
+    },
+    {
+        L"Software\\Python",
+        HKEY_LOCAL_MACHINE,
+        KEY_READ | KEY_WOW64_32KEY,
+        4,
+        L"32bit"
+    },
+    { NULL, 0, 0, 0, NULL }
+};
+
+
+struct AppxSearchInfo {
+    // The package family name. Can be found for an installed package using the
+    // Powershell "Get-AppxPackage" cmdlet
+    const wchar_t *familyName;
+    // The tag to treat the installation as
+    const wchar_t *tag;
+    // Internal sort key to select between "identical" environments discovered
+    // through different methods
+    int sortKey;
+};
+
+
+struct AppxSearchInfo APPX_SEARCH[] = {
+    // Releases made through the Store
+    { L"PythonSoftwareFoundation.Python.3.11_qbz5n2kfra8p0", L"3.11", 10 },
+    { L"PythonSoftwareFoundation.Python.3.10_qbz5n2kfra8p0", L"3.10", 10 },
+    { L"PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0", L"3.9", 10 },
+    { L"PythonSoftwareFoundation.Python.3.8_qbz5n2kfra8p0", L"3.8", 10 },
+
+    // Side-loadable releases. Note that the publisher ID changes whenever we
+    // renew our code-signing certificate, so the newer ID has a higher
+    // priority (lower sortKey)
+    { L"PythonSoftwareFoundation.Python.3.11_3847v3x7pw1km", L"3.11", 11 },
+    { L"PythonSoftwareFoundation.Python.3.11_hd69rhyc2wevp", L"3.11", 12 },
+    { L"PythonSoftwareFoundation.Python.3.10_3847v3x7pw1km", L"3.10", 11 },
+    { L"PythonSoftwareFoundation.Python.3.10_hd69rhyc2wevp", L"3.10", 12 },
+    { L"PythonSoftwareFoundation.Python.3.9_3847v3x7pw1km", L"3.9", 11 },
+    { L"PythonSoftwareFoundation.Python.3.9_hd69rhyc2wevp", L"3.9", 12 },
+    { L"PythonSoftwareFoundation.Python.3.8_hd69rhyc2wevp", L"3.8", 12 },
+    { NULL, NULL, 0 }
+};
+
+
+int
+collectEnvironments(const SearchInfo *search, EnvironmentInfo **result)
+{
+    int exitCode = 0;
+    EnvironmentInfo *env = NULL;
+    if (!result) {
+        return RC_INTERNAL_ERROR;
+    }
+    *result = NULL;
+
+    if (search->executablePath) {
+        env = newEnvironmentInfo(NULL, NULL);
+        return copyWstr(&env->executablePath, search->executablePath);
+    }
+
+    HKEY root;
+
+    for (struct RegistrySearchInfo *info = REGISTRY_SEARCH; info->subkey; ++info) {
+        if (ERROR_SUCCESS == RegOpenKeyExW(info->hive, info->subkey, 0, info->flags, &root)) {
+            exitCode = registrySearch(search, result, root, info->sortKey, info->fallbackArch);
+            RegCloseKey(root);
+        }
+        if (exitCode) {
+            return exitCode;
+        }
+    }
+
+    for (struct AppxSearchInfo *info = APPX_SEARCH; info->familyName; ++info) {
+        exitCode = appxSearch(search, result, info->familyName, info->tag, info->sortKey);
+        if (exitCode && exitCode != RC_NO_PYTHON) {
+            return exitCode;
+        }
+    }
+
+    return 0;
+}
+
+
+/******************************************************************************\
+ ***                           INSTALL ON DEMAND                            ***
+\******************************************************************************/
+
+struct StoreSearchInfo {
+    // The tag a user is looking for
+    const wchar_t *tag;
+    // The Store ID for a package if it can be installed from the Microsoft
+    // Store. These are obtained from the dashboard at
+    // https://partner.microsoft.com/dashboard
+    const wchar_t *storeId;
+};
+
+
+struct StoreSearchInfo STORE_SEARCH[] = {
+    { L"3", /* 3.10 */ L"9PJPW5LDXLZ5" },
+    { L"3.11", L"9NRWMJP3717K" },
+    { L"3.10", L"9PJPW5LDXLZ5" },
+    { L"3.9", L"9P7QFQMJRFP7" },
+    { L"3.8", L"9MSSZTT1N39L" },
+    { NULL, NULL }
+};
+
+
+int
+_installEnvironment(const wchar_t *command, const wchar_t *arguments)
+{
+    SHELLEXECUTEINFOW siw = {
+        sizeof(SHELLEXECUTEINFOW),
+        SEE_MASK_NOASYNC | SEE_MASK_NOCLOSEPROCESS | SEE_MASK_NO_CONSOLE,
+        NULL, NULL,
+        command, arguments, NULL,
+        SW_SHOWNORMAL
+    };
+
+    debug(L"# Installing with %s %s\n", command, arguments);
+    if (isEnvVarSet(L"PYLAUNCHER_DRYRUN")) {
+        debug(L"# Exiting due to PYLAUNCHER_DRYRUN\n");
+        fflush(stdout);
+        int mode = _setmode(_fileno(stdout), _O_U8TEXT);
+        if (arguments) {
+            fwprintf_s(stdout, L"\"%s\" %s\n", command, arguments);
+        } else {
+            fwprintf_s(stdout, L"\"%s\"\n", command);
+        }
+        fflush(stdout);
+        if (mode >= 0) {
+            _setmode(_fileno(stdout), mode);
+        }
+        return RC_INSTALLING;
+    }
+
+    if (!ShellExecuteExW(&siw)) {
+        return RC_NO_PYTHON;
+    }
+
+    if (!siw.hProcess) {
+        return RC_INSTALLING;
+    }
+
+    WaitForSingleObjectEx(siw.hProcess, INFINITE, FALSE);
+    DWORD exitCode = 0;
+    if (GetExitCodeProcess(siw.hProcess, &exitCode) && exitCode == 0) {
+        return 0;
+    }
+    return RC_INSTALLING;
+}
+
+
+const wchar_t *WINGET_COMMAND = L"Microsoft\\WindowsApps\\Microsoft.DesktopAppInstaller_8wekyb3d8bbwe\\winget.exe";
+const wchar_t *WINGET_ARGUMENTS = L"install -q %s --exact --accept-package-agreements --source msstore";
+
+const wchar_t *MSSTORE_COMMAND = L"ms-windows-store://pdp/?productid=%s";
+
+int
+installEnvironment(const SearchInfo *search)
+{
+    // No tag? No installing
+    if (!search->tag || !search->tagLength) {
+        debug(L"# Cannot install Python with no tag specified\n");
+        return RC_NO_PYTHON;
+    }
+
+    // PEP 514 tag but not PythonCore? No installing
+    if (!search->oldStyleTag &&
+        search->company && search->companyLength &&
+        0 != _compare(search->company, search->companyLength, L"PythonCore", -1)) {
+        debug(L"# Cannot install for company %.*s\n", search->companyLength, search->company);
+        return RC_NO_PYTHON;
+    }
+
+    const wchar_t *storeId = NULL;
+    for (struct StoreSearchInfo *info = STORE_SEARCH; info->tag; ++info) {
+        if (0 == _compare(search->tag, search->tagLength, info->tag, -1)) {
+            storeId = info->storeId;
+            break;
+        }
+    }
+
+    if (!storeId) {
+        return RC_NO_PYTHON;
+    }
+
+    int exitCode;
+    wchar_t command[MAXLEN];
+    wchar_t arguments[MAXLEN];
+    if (SUCCEEDED(SHGetFolderPathW(NULL, CSIDL_LOCAL_APPDATA, NULL, 0, command)) &&
+        join(command, MAXLEN, WINGET_COMMAND) &&
+        swprintf_s(arguments, MAXLEN, WINGET_ARGUMENTS, storeId)) {
+        if (INVALID_FILE_ATTRIBUTES == GetFileAttributesW(command)) {
+            formatWinerror(GetLastError(), arguments, MAXLEN);
+            debug(L"# Skipping %s: %s\n", command, arguments);
+        } else {
+            fputws(L"Launching winget to install Python. The following output is from the install process\n\
+***********************************************************************\n", stdout);
+            exitCode = _installEnvironment(command, arguments);
+            if (exitCode == RC_INSTALLING) {
+                fputws(L"***********************************************************************\n\
+Please check the install status and run your command again.", stderr);
+                return exitCode;
+            } else if (exitCode) {
+                return exitCode;
+            }
+            fputws(L"***********************************************************************\n\
+Install appears to have succeeded. Searching for new matching installs.\n", stdout);
+            return 0;
+        }
+    }
+
+    if (swprintf_s(command, MAXLEN, MSSTORE_COMMAND, storeId)) {
+        fputws(L"Opening the Microsoft Store to install Python. After installation, "
+               L"please run your command again.\n", stderr);
+        exitCode = _installEnvironment(command, NULL);
+        if (exitCode) {
+            return exitCode;
+        }
+        return 0;
+    }
+
+    return RC_NO_PYTHON;
+}
+
+/******************************************************************************\
+ ***                           ENVIRONMENT SELECT                           ***
+\******************************************************************************/
+
+bool
+_companyMatches(const SearchInfo *search, const EnvironmentInfo *env)
+{
+    if (!search->company || !search->companyLength) {
+        return true;
+    }
+    return 0 == _compare(env->company, -1, search->company, search->companyLength);
+}
+
+
+bool
+_tagMatches(const SearchInfo *search, const EnvironmentInfo *env)
+{
+    if (!search->tag || !search->tagLength) {
+        return true;
+    }
+    return _startsWith(env->tag, -1, search->tag, search->tagLength);
+}
+
+
+bool
+_is32Bit(const EnvironmentInfo *env)
+{
+    if (env->architecture) {
+        return 0 == _compare(env->architecture, -1, L"32bit", -1);
+    }
+    return false;
+}
+
+
+int
+_selectEnvironment(const SearchInfo *search, EnvironmentInfo *env, EnvironmentInfo **best)
+{
+    int exitCode = 0;
+    while (env) {
+        exitCode = _selectEnvironment(search, env->prev, best);
+
+        if (exitCode && exitCode != RC_NO_PYTHON) {
+            return exitCode;
+        } else if (!exitCode && *best) {
+            return 0;
+        }
+
+        if (!search->oldStyleTag) {
+            if (_companyMatches(search, env) && _tagMatches(search, env)) {
+                // Because of how our sort tree is set up, we will walk up the
+                // "prev" side and implicitly select the "best" best. By
+                // returning straight after a match, we skip the entire "next"
+                // branch and won't ever select a "worse" best.
+                *best = env;
+                return 0;
+            }
+        } else if (0 == _compare(env->company, -1, L"PythonCore", -1)) {
+            // Old-style tags can only match PythonCore entries
+            if (_startsWith(env->tag, -1, search->tag, search->tagLength)) {
+                if (search->exclude32Bit && _is32Bit(env)) {
+                    debug(L"# Excluding %s/%s because it looks like 32bit\n", env->company, env->tag);
+                } else if (search->only32Bit && !_is32Bit(env)) {
+                    debug(L"# Excluding %s/%s because it doesn't look 32bit\n", env->company, env->tag);
+                } else {
+                    *best = env;
+                    return 0;
+                }
+            }
+        }
+
+        env = env->next;
+    }
+    return RC_NO_PYTHON;
+}
+
+int
+selectEnvironment(const SearchInfo *search, EnvironmentInfo *root, EnvironmentInfo **best)
+{
+    if (!best) {
+        return RC_INTERNAL_ERROR;
+    }
+    if (!root) {
+        *best = NULL;
+        return RC_NO_PYTHON_AT_ALL;
+    }
+    if (!root->next && !root->prev) {
+        *best = root;
+        return 0;
+    }
+
+    EnvironmentInfo *result = NULL;
+    int exitCode = _selectEnvironment(search, root, &result);
+    if (!exitCode) {
+        *best = result;
+    }
+
+    return exitCode;
+}
+
+
+/******************************************************************************\
+ ***                            LIST ENVIRONMENTS                           ***
+\******************************************************************************/
+
+#define TAGWIDTH 16
+
+int
+_printEnvironment(const EnvironmentInfo *env, FILE *out, bool showPath, const wchar_t *argument)
+{
+    if (showPath) {
+        if (env->executablePath && env->executablePath[0]) {
+            if (env->executableArgs && env->executableArgs[0]) {
+                fwprintf(out, L" %-*s %s %s\n", TAGWIDTH, argument, env->executablePath, env->executableArgs);
+            } else {
+                fwprintf(out, L" %-*s %s\n", TAGWIDTH, argument, env->executablePath);
+            }
+        } else if (env->installDir && env->installDir[0]) {
+            fwprintf(out, L" %-*s %s\n", TAGWIDTH, argument, env->installDir);
+        } else {
+            fwprintf(out, L" %s\n", argument);
+        }
+    } else if (env->displayName) {
+        fwprintf(out, L" %-*s %s\n", TAGWIDTH, argument, env->displayName);
+    } else {
+        fwprintf(out, L" %s\n", argument);
+    }
+    return 0;
+}
+
+
+int
+_listAllEnvironments(EnvironmentInfo *env, FILE * out, bool showPath, bool *isDefault)
+{
+    wchar_t buffer[256];
+    while (env) {
+        int exitCode = _listAllEnvironments(env->prev, out, showPath, isDefault);
+        if (exitCode) {
+            return exitCode;
+        }
+
+        if (!env->company || !env->tag) {
+            buffer[0] = L'\0';
+        } else if (0 == _compare(env->company, -1, L"PythonCore", -1)) {
+            swprintf_s(buffer, sizeof(buffer) / sizeof(buffer[0]), L"-V:%s", env->tag);
+        } else {
+            swprintf_s(buffer, sizeof(buffer) / sizeof(buffer[0]), L"-V:%s/%s", env->company, env->tag);
+        }
+        if (buffer[0]) {
+            if (*isDefault) {
+                wcscat_s(buffer, sizeof(buffer) / sizeof(buffer[0]), L" *");
+                *isDefault = false;
+            }
+            exitCode = _printEnvironment(env, out, showPath, buffer);
+            if (exitCode) {
+                return exitCode;
+            }
+        }
+
+        env = env->next;
+    }
+    return 0;
+}
+
+
+int
+listEnvironments(EnvironmentInfo *env, FILE * out, bool showPath)
+{
+    bool isDefault = true;
+
+    if (!env) {
+        fwprintf_s(stdout, L"No installed Pythons found!\n");
+        return 0;
+    }
+
+    /* TODO: Do we want to display these?
+       In favour, helps users see that '-3' is a good option
+       Against, repeats the next line of output
+    SearchInfo majorSearch;
+    EnvironmentInfo *major;
+    int exitCode;
+
+    if (showPath) {
+        memset(&majorSearch, 0, sizeof(majorSearch));
+        majorSearch.company = L"PythonCore";
+        majorSearch.companyLength = -1;
+        majorSearch.tag = L"3";
+        majorSearch.tagLength = -1;
+        majorSearch.oldStyleTag = true;
+        major = NULL;
+        exitCode = selectEnvironment(&majorSearch, env, &major);
+        if (!exitCode && major) {
+            exitCode = _printEnvironment(major, out, showPath, L"-3 *");
+            isDefault = false;
+            if (exitCode) {
+                return exitCode;
+            }
+        }
+        majorSearch.tag = L"2";
+        major = NULL;
+        exitCode = selectEnvironment(&majorSearch, env, &major);
+        if (!exitCode && major) {
+            exitCode = _printEnvironment(major, out, showPath, L"-2");
+            if (exitCode) {
+                return exitCode;
+            }
+        }
+    }
+    */
+
+    int mode = _setmode(_fileno(out), _O_U8TEXT);
+    int exitCode = _listAllEnvironments(env, out, showPath, &isDefault);
+    fflush(out);
+    if (mode >= 0) {
+        _setmode(_fileno(out), mode);
+    }
+    return exitCode;
+}
+
+
+/******************************************************************************\
+ ***                           INTERPRETER LAUNCH                           ***
+\******************************************************************************/
+
+
+int
+calculateCommandLine(const SearchInfo *search, const EnvironmentInfo *launch, wchar_t *buffer, int bufferLength)
+{
+    int exitCode = 0;
+    const wchar_t *executablePath = NULL;
+
+    // Construct command line from a search override, or else the selected
+    // environment's executablePath
+    if (search->executablePath) {
+        executablePath = search->executablePath;
+    } else if (launch && launch->executablePath) {
+        executablePath = launch->executablePath;
+    }
+
+    // If we have an executable path, put it at the start of the command, but
+    // only if the search allowed an override.
+    // Otherwise, use the environment's installDir and the search's default
+    // executable name.
+    if (executablePath && search->allowExecutableOverride) {
+        if (wcschr(executablePath, L' ') && executablePath[0] != L'"') {
+            buffer[0] = L'"';
+            exitCode = wcscpy_s(&buffer[1], bufferLength - 1, executablePath);
+            if (!exitCode) {
+                exitCode = wcscat_s(buffer, bufferLength, L"\"");
+            }
+        } else {
+            exitCode = wcscpy_s(buffer, bufferLength, executablePath);
+        }
+    } else if (launch) {
+        if (!launch->installDir) {
+            fwprintf_s(stderr, L"Cannot launch %s %s because no install directory was specified",
+                       launch->company, launch->tag);
+            exitCode = RC_NO_PYTHON;
+        } else if (!search->executable || !search->executableLength) {
+            fwprintf_s(stderr, L"Cannot launch %s %s because no executable name is available",
+                       launch->company, launch->tag);
+            exitCode = RC_NO_PYTHON;
+        } else {
+            wchar_t executable[256];
+            wcsncpy_s(executable, 256, search->executable, search->executableLength);
+            if ((wcschr(launch->installDir, L' ') && launch->installDir[0] != L'"') ||
+                (wcschr(executable, L' ') && executable[0] != L'"')) {
+                buffer[0] = L'"';
+                exitCode = wcscpy_s(&buffer[1], bufferLength - 1, launch->installDir);
+                if (!exitCode) {
+                    exitCode = join(buffer, bufferLength, executable) ? 0 : RC_NO_MEMORY;
+                }
+                if (!exitCode) {
+                    exitCode = wcscat_s(buffer, bufferLength, L"\"");
+                }
+            } else {
+                exitCode = wcscpy_s(buffer, bufferLength, launch->installDir);
+                if (!exitCode) {
+                    exitCode = join(buffer, bufferLength, executable) ? 0 : RC_NO_MEMORY;
+                }
+            }
+        }
+    } else {
+        exitCode = RC_NO_PYTHON;
+    }
+
+    if (!exitCode && launch && launch->executableArgs) {
+        exitCode = wcscat_s(buffer, bufferLength, L" ");
+        if (!exitCode) {
+            exitCode = wcscat_s(buffer, bufferLength, launch->executableArgs);
+        }
+    }
+
+    if (!exitCode && search->executableArgs) {
+        if (search->executableArgsLength < 0) {
+            exitCode = wcscat_s(buffer, bufferLength, search->executableArgs);
+        } else if (search->executableArgsLength > 0) {
+            int end = (int)wcsnlen_s(buffer, MAXLEN);
+            if (end < bufferLength - (search->executableArgsLength + 1)) {
+                exitCode = wcsncpy_s(&buffer[end], bufferLength - end,
+                    search->executableArgs, search->executableArgsLength);
+            }
+        }
+    }
+
+    if (!exitCode && search->restOfCmdLine) {
+        exitCode = wcscat_s(buffer, bufferLength, search->restOfCmdLine);
+    }
+
+    return exitCode;
+}
+
+
+
+BOOL
+_safeDuplicateHandle(HANDLE in, HANDLE * pout, const wchar_t *nameForError)
+{
+    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 returned ERROR_INVALID_HANDLE\n");
+            ok = TRUE;
+        }
+        else {
+            winerror(0, L"Failed to duplicate %s handle", nameForError);
+        }
+    }
+    return ok;
+}
+
+BOOL WINAPI
+ctrl_c_handler(DWORD code)
+{
+    return TRUE;    /* We just ignore all control events. */
+}
+
+
+int
+launchEnvironment(const SearchInfo *search, const EnvironmentInfo *launch, wchar_t *launchCommand)
+{
+    HANDLE job;
+    JOBOBJECT_EXTENDED_LIMIT_INFORMATION info;
+    DWORD rc;
+    BOOL ok;
+    STARTUPINFOW si;
+    PROCESS_INFORMATION pi;
+
+    // If this is a dryrun, do not actually launch
+    if (isEnvVarSet(L"PYLAUNCHER_DRYRUN")) {
+        debug(L"LaunchCommand: %s\n", launchCommand);
+        debug(L"# Exiting due to PYLAUNCHER_DRYRUN variable\n");
+        fflush(stdout);
+        int mode = _setmode(_fileno(stdout), _O_U8TEXT);
+        fwprintf(stdout, L"%s\n", launchCommand);
+        fflush(stdout);
+        if (mode >= 0) {
+            _setmode(_fileno(stdout), mode);
+        }
+        return 0;
+    }
+
+#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 and
+    https://bitbucket.org/vinay.sajip/pylauncher/issue/20/busy-cursor-for-a-long-time-when-running
+    */
+    MSG msg;
+
+    PostMessage(0, 0, 0, 0);
+    GetMessage(&msg, 0, 0, 0);
+#endif
+
+    debug(L"# about to run: %s\n", launchCommand);
+    job = CreateJobObject(NULL, NULL);
+    ok = QueryInformationJobObject(job, JobObjectExtendedLimitInformation,
+                                  &info, sizeof(info), &rc);
+    if (!ok || (rc != sizeof(info)) || !job) {
+        winerror(0, L"Failed to query job information");
+        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(0, L"Failed to update job information");
+        return RC_CREATE_PROCESS;
+    }
+    memset(&si, 0, sizeof(si));
+    GetStartupInfoW(&si);
+    if (!_safeDuplicateHandle(GetStdHandle(STD_INPUT_HANDLE), &si.hStdInput, L"stdin") ||
+        !_safeDuplicateHandle(GetStdHandle(STD_OUTPUT_HANDLE), &si.hStdOutput, L"stdout") ||
+        !_safeDuplicateHandle(GetStdHandle(STD_ERROR_HANDLE), &si.hStdError, L"stderr")) {
+        return RC_NO_STD_HANDLES;
+    }
+
+    ok = SetConsoleCtrlHandler(ctrl_c_handler, TRUE);
+    if (!ok) {
+        winerror(0, L"Failed to update Control-C handler");
+        return RC_NO_STD_HANDLES;
+    }
+
+    si.dwFlags = STARTF_USESTDHANDLES;
+    ok = CreateProcessW(NULL, launchCommand, NULL, NULL, TRUE,
+                        0, NULL, NULL, &si, &pi);
+    if (!ok) {
+        winerror(0, L"Unable to create process using '%s'", launchCommand);
+        return RC_CREATE_PROCESS;
+    }
+    AssignProcessToJobObject(job, pi.hProcess);
+    CloseHandle(pi.hThread);
+    WaitForSingleObjectEx(pi.hProcess, INFINITE, FALSE);
+    ok = GetExitCodeProcess(pi.hProcess, &rc);
+    if (!ok) {
+        winerror(0, L"Failed to get exit code of process");
+        return RC_CREATE_PROCESS;
+    }
+    debug(L"child process exit code: %d\n", rc);
+    return rc;
+}
+
+
+/******************************************************************************\
+ ***                           PROCESS CONTROLLER                           ***
+\******************************************************************************/
+
+
+int
+performSearch(SearchInfo *search, EnvironmentInfo **envs)
+{
+    // First parse the command line for options
+    int exitCode = parseCommandLine(search);
+    if (exitCode) {
+        return exitCode;
+    }
+
+    // Check for a shebang line in our script file
+    // (or return quickly if no script file was specified)
+    exitCode = checkShebang(search);
+    if (exitCode) {
+        return exitCode;
+    }
+
+    // Resolve old-style tags (possibly from a shebang) against py.ini entries
+    // and environment variables.
+    exitCode = checkDefaults(search);
+    if (exitCode) {
+        return exitCode;
+    }
+
+    // If debugging is enabled, list our search criteria
+    dumpSearchInfo(search);
+
+    // Find all matching environments
+    exitCode = collectEnvironments(search, envs);
+    if (exitCode) {
+        return exitCode;
+    }
+
+    return 0;
+}
+
+
+int
+process(int argc, wchar_t ** argv)
+{
+    int exitCode = 0;
+    SearchInfo search = {0};
+    EnvironmentInfo *envs = NULL;
+    EnvironmentInfo *env = NULL;
+    wchar_t launchCommand[MAXLEN];
+
+    memset(launchCommand, 0, sizeof(launchCommand));
+
+    if (isEnvVarSet(L"PYLAUNCHER_DEBUG")) {
+        setvbuf(stderr, (char *)NULL, _IONBF, 0);
+        log_fp = stderr;
+        debug(L"argv0: %s\nversion: %S\n", argv[0], PY_VERSION);
+    }
+
+    search.originalCmdLine = GetCommandLineW();
+
+    exitCode = performSearch(&search, &envs);
+    if (exitCode) {
+        goto abort;
+    }
+
+    // Display the help text, but only exit on error
+    if (search.help) {
+        exitCode = showHelpText(argv);
+        if (exitCode) {
+            goto abort;
+        }
+    }
+
+    // List all environments, then exit
+    if (search.list || search.listPaths) {
+        exitCode = listEnvironments(envs, stdout, search.listPaths);
+        goto abort;
+    }
+
+    // When debugging, list all discovered environments anyway
+    if (log_fp) {
+        exitCode = listEnvironments(envs, log_fp, true);
+        if (exitCode) {
+            goto abort;
+        }
+    }
+
+    // Select best environment
+    env = NULL;
+    if (search.executablePath == NULL) {
+        exitCode = selectEnvironment(&search, envs, &env);
+        // If none found, and if permitted, install it
+        if (exitCode == RC_NO_PYTHON && isEnvVarSet(L"PYLAUNCHER_ALLOW_INSTALL") ||
+            isEnvVarSet(L"PYLAUNCHER_ALWAYS_INSTALL")) {
+            exitCode = installEnvironment(&search);
+            if (!exitCode) {
+                // Successful install, so we need to re-scan and select again
+                exitCode = performSearch(&search, &envs);
+                if (exitCode) {
+                    goto abort;
+                }
+                env = NULL;
+                exitCode = selectEnvironment(&search, envs, &env);
+            }
+        }
+        if (exitCode == RC_NO_PYTHON) {
+            fputws(L"No suitable Python runtime found\n", stderr);
+            fputws(L"Pass --list (-0) to see all detected environments on your machine\n", stderr);
+            if (!isEnvVarSet(L"PYLAUNCHER_ALLOW_INSTALL") && search.oldStyleTag) {
+                fputws(L"or set environment variable PYLAUNCHER_ALLOW_INSTALL to use winget\n"
+                       L"or open the Microsoft Store to the requested version.\n", stderr);
+            }
+            goto abort;
+        }
+        if (exitCode == RC_NO_PYTHON_AT_ALL) {
+            fputws(L"No installed Python found!\n", stderr);
+            goto abort;
+        }
+        if (exitCode) {
+            goto abort;
+        }
+
+        if (env) {
+            debug(L"env.company: %s\nenv.tag: %s\n", env->company, env->tag);
+        } else {
+            debug(L"env.company: (null)\nenv.tag: (null)\n");
+        }
+    }
+
+    exitCode = calculateCommandLine(&search, env, launchCommand, sizeof(launchCommand) / sizeof(launchCommand[0]));
+    if (exitCode) {
+        goto abort;
+    }
+
+    // Launch selected runtime
+    exitCode = launchEnvironment(&search, env, launchCommand);
+
+abort:
+    freeSearchInfo(&search);
+    freeEnvironmentInfo(envs);
+    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