/* Return the initial module search path. */

#include "Python.h"
#include "pycore_initconfig.h"
#include "osdefs.h"
#include "pycore_fileutils.h"
#include "pycore_pathconfig.h"
#include "pycore_pystate.h"

#include <sys/types.h>
#include <string.h>

#ifdef __APPLE__
# include <mach-o/dyld.h>
#endif

/* Search in some common locations for the associated Python libraries.
 *
 * Two directories must be found, the platform independent directory
 * (prefix), containing the common .py and .pyc files, and the platform
 * dependent directory (exec_prefix), containing the shared library
 * modules. Note that prefix and exec_prefix can be the same directory,
 * but for some installations, they are different.
 *
 * Py_GetPath() carries out separate searches for prefix and exec_prefix.
 * Each search tries a number of different locations until a ``landmark''
 * file or directory is found. If no prefix or exec_prefix is found, a
 * warning message is issued and the preprocessor defined PREFIX and
 * EXEC_PREFIX are used (even though they will not work); python carries on
 * as best as is possible, but most imports will fail.
 *
 * Before any searches are done, the location of the executable is
 * determined. If argv[0] has one or more slashes in it, it is used
 * unchanged. Otherwise, it must have been invoked from the shell's path,
 * so we search $PATH for the named executable and use that. If the
 * executable was not found on $PATH (or there was no $PATH environment
 * variable), the original argv[0] string is used.
 *
 * Next, the executable location is examined to see if it is a symbolic
 * link. If so, the link is chased (correctly interpreting a relative
 * pathname if one is found) and the directory of the link target is used.
 *
 * Finally, argv0_path is set to the directory containing the executable
 * (i.e. the last component is stripped).
 *
 * With argv0_path in hand, we perform a number of steps. The same steps
 * are performed for prefix and for exec_prefix, but with a different
 * landmark.
 *
 * Step 1. Are we running python out of the build directory? This is
 * checked by looking for a different kind of landmark relative to
 * argv0_path. For prefix, the landmark's path is derived from the VPATH
 * preprocessor variable (taking into account that its value is almost, but
 * not quite, what we need). For exec_prefix, the landmark is
 * pybuilddir.txt. If the landmark is found, we're done.
 *
 * For the remaining steps, the prefix landmark will always be
 * lib/python$VERSION/os.py and the exec_prefix will always be
 * lib/python$VERSION/lib-dynload, where $VERSION is Python's version
 * number as supplied by the Makefile. Note that this means that no more
 * build directory checking is performed; if the first step did not find
 * the landmarks, the assumption is that python is running from an
 * installed setup.
 *
 * Step 2. See if the $PYTHONHOME environment variable points to the
 * installed location of the Python libraries. If $PYTHONHOME is set, then
 * it points to prefix and exec_prefix. $PYTHONHOME can be a single
 * directory, which is used for both, or the prefix and exec_prefix
 * directories separated by a colon.
 *
 * Step 3. Try to find prefix and exec_prefix relative to argv0_path,
 * backtracking up the path until it is exhausted. This is the most common
 * step to succeed. Note that if prefix and exec_prefix are different,
 * exec_prefix is more likely to be found; however if exec_prefix is a
 * subdirectory of prefix, both will be found.
 *
 * Step 4. Search the directories pointed to by the preprocessor variables
 * PREFIX and EXEC_PREFIX. These are supplied by the Makefile but can be
 * passed in as options to the configure script.
 *
 * That's it!
 *
 * Well, almost. Once we have determined prefix and exec_prefix, the
 * preprocessor variable PYTHONPATH is used to construct a path. Each
 * relative path on PYTHONPATH is prefixed with prefix. Then the directory
 * containing the shared library modules is appended. The environment
 * variable $PYTHONPATH is inserted in front of it all. Finally, the
 * prefix and exec_prefix globals are tweaked so they reflect the values
 * expected by other code, by stripping the "lib/python$VERSION/..." stuff
 * off. If either points to the build directory, the globals are reset to
 * the corresponding preprocessor variables (so sys.prefix will reflect the
 * installation location, even though sys.path points into the build
 * directory). This seems to make more sense given that currently the only
 * known use of sys.prefix and sys.exec_prefix is for the ILU installation
 * process to find the installed Python tree.
 *
 * An embedding application can use Py_SetPath() to override all of
 * these authomatic path computations.
 *
 * NOTE: Windows MSVC builds use PC/getpathp.c instead!
 */

#ifdef __cplusplus
extern "C" {
#endif


#if !defined(PREFIX) || !defined(EXEC_PREFIX) || !defined(VERSION) || !defined(VPATH)
#error "PREFIX, EXEC_PREFIX, VERSION, and VPATH must be constant defined"
#endif

#ifndef LANDMARK
#define LANDMARK L"os.py"
#endif

#define DECODE_LOCALE_ERR(NAME, LEN) \
 ((LEN) == (size_t)-2) \
 ? _PyStatus_ERR("cannot decode " NAME) \
 : _PyStatus_NO_MEMORY()

#define PATHLEN_ERR() _PyStatus_ERR("path configuration: path too long")

typedef struct {
 wchar_t *path_env; /* PATH environment variable */

 wchar_t *pythonpath; /* PYTHONPATH macro */
 wchar_t *prefix; /* PREFIX macro */
 wchar_t *exec_prefix; /* EXEC_PREFIX macro */

 wchar_t *lib_python; /* "lib/pythonX.Y" */

 int prefix_found; /* found platform independent libraries? */
 int exec_prefix_found; /* found the platform dependent libraries? */

 int warnings;
 const wchar_t *pythonpath_env;
} PyCalculatePath;

static const wchar_t delimiter[2] = {DELIM, '0円'};
static const wchar_t separator[2] = {SEP, '0円'};


/* Get file status. Encode the path to the locale encoding. */
static int
_Py_wstat(const wchar_t* path, struct stat *buf)
{
 int err;
 char *fname;
 fname = _Py_EncodeLocaleRaw(path, NULL);
 if (fname == NULL) {
 errno = EINVAL;
 return -1;
 }
 err = stat(fname, buf);
 PyMem_RawFree(fname);
 return err;
}


static void
reduce(wchar_t *dir)
{
 size_t i = wcslen(dir);
 while (i > 0 && dir[i] != SEP) {
 --i;
 }
 dir[i] = '0円';
}


/* Is file, not directory */
static int
isfile(const wchar_t *filename)
{
 struct stat buf;
 if (_Py_wstat(filename, &buf) != 0) {
 return 0;
 }
 if (!S_ISREG(buf.st_mode)) {
 return 0;
 }
 return 1;
}


/* Is module -- check for .pyc too */
static int
ismodule(wchar_t *filename, size_t filename_len)
{
 if (isfile(filename)) {
 return 1;
 }

 /* Check for the compiled version of prefix. */
 if (wcslen(filename) + 2 <= filename_len) {
 wcscat(filename, L"c");
 if (isfile(filename)) {
 return 1;
 }
 }
 return 0;
}


/* Is executable file */
static int
isxfile(const wchar_t *filename)
{
 struct stat buf;
 if (_Py_wstat(filename, &buf) != 0) {
 return 0;
 }
 if (!S_ISREG(buf.st_mode)) {
 return 0;
 }
 if ((buf.st_mode & 0111) == 0) {
 return 0;
 }
 return 1;
}


/* Is directory */
static int
isdir(wchar_t *filename)
{
 struct stat buf;
 if (_Py_wstat(filename, &buf) != 0) {
 return 0;
 }
 if (!S_ISDIR(buf.st_mode)) {
 return 0;
 }
 return 1;
}


/* Add a path component, by appending stuff to buffer.
 buflen: 'buffer' length in characters including trailing NUL. */
static PyStatus
joinpath(wchar_t *buffer, const wchar_t *stuff, size_t buflen)
{
 size_t n, k;
 if (stuff[0] != SEP) {
 n = wcslen(buffer);
 if (n >= buflen) {
 return PATHLEN_ERR();
 }

 if (n > 0 && buffer[n-1] != SEP) {
 buffer[n++] = SEP;
 }
 }
 else {
 n = 0;
 }

 k = wcslen(stuff);
 if (n + k >= buflen) {
 return PATHLEN_ERR();
 }
 wcsncpy(buffer+n, stuff, k);
 buffer[n+k] = '0円';

 return _PyStatus_OK();
}


static inline int
safe_wcscpy(wchar_t *dst, const wchar_t *src, size_t n)
{
 size_t srclen = wcslen(src);
 if (n <= srclen) {
 dst[0] = L'0円';
 return -1;
 }
 memcpy(dst, src, (srclen + 1) * sizeof(wchar_t));
 return 0;
}


/* copy_absolute requires that path be allocated at least
 'pathlen' characters (including trailing NUL). */
static PyStatus
copy_absolute(wchar_t *path, const wchar_t *p, size_t pathlen)
{
 if (p[0] == SEP) {
 if (safe_wcscpy(path, p, pathlen) < 0) {
 return PATHLEN_ERR();
 }
 }
 else {
 if (!_Py_wgetcwd(path, pathlen)) {
 /* unable to get the current directory */
 if (safe_wcscpy(path, p, pathlen) < 0) {
 return PATHLEN_ERR();
 }
 return _PyStatus_OK();
 }
 if (p[0] == '.' && p[1] == SEP) {
 p += 2;
 }
 PyStatus status = joinpath(path, p, pathlen);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }
 return _PyStatus_OK();
}


/* path_len: path length in characters including trailing NUL */
static PyStatus
absolutize(wchar_t *path, size_t path_len)
{
 if (path[0] == SEP) {
 return _PyStatus_OK();
 }

 wchar_t abs_path[MAXPATHLEN+1];
 PyStatus status = copy_absolute(abs_path, path, Py_ARRAY_LENGTH(abs_path));
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (safe_wcscpy(path, abs_path, path_len) < 0) {
 return PATHLEN_ERR();
 }
 return _PyStatus_OK();
}


#if defined(__CYGWIN__) || defined(__MINGW32__)
#ifndef EXE_SUFFIX
#define EXE_SUFFIX L".exe"
#endif

/* pathlen: 'path' length in characters including trailing NUL */
static PyStatus
add_exe_suffix(wchar_t *progpath, size_t progpathlen)
{
 /* Check for already have an executable suffix */
 size_t n = wcslen(progpath);
 size_t s = wcslen(EXE_SUFFIX);
 if (wcsncasecmp(EXE_SUFFIX, progpath + n - s, s) == 0) {
 return _PyStatus_OK();
 }

 if (n + s >= progpathlen) {
 return PATHLEN_ERR();
 }
 wcsncpy(progpath + n, EXE_SUFFIX, s);
 progpath[n+s] = '0円';

 if (!isxfile(progpath)) {
 /* Path that added suffix is invalid: truncate (remove suffix) */
 progpath[n] = '0円';
 }

 return _PyStatus_OK();
}
#endif


/* search_for_prefix requires that argv0_path be no more than MAXPATHLEN
 bytes long.
*/
static PyStatus
search_for_prefix(PyCalculatePath *calculate, _PyPathConfig *pathconfig,
 const wchar_t *argv0_path,
 wchar_t *prefix, size_t prefix_len, int *found)
{
 wchar_t path[MAXPATHLEN+1];
 memset(path, 0, sizeof(path));
 size_t path_len = Py_ARRAY_LENGTH(path);

 PyStatus status;

 /* If PYTHONHOME is set, we believe it unconditionally */
 if (pathconfig->home) {
 /* Path: <home> / <lib_python> */
 if (safe_wcscpy(prefix, pathconfig->home, prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 wchar_t *delim = wcschr(prefix, DELIM);
 if (delim) {
 *delim = L'0円';
 }
 status = joinpath(prefix, calculate->lib_python, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 *found = 1;
 return _PyStatus_OK();
 }

 /* Check to see if argv[0] is in the build directory */
 if (safe_wcscpy(path, argv0_path, path_len) < 0) {
 return PATHLEN_ERR();
 }
 status = joinpath(path, L"Modules/Setup.local", path_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (isfile(path)) {
 /* Check VPATH to see if argv0_path is in the build directory.
 VPATH can be empty. */
 wchar_t *vpath = Py_DecodeLocale(VPATH, NULL);
 if (vpath != NULL) {
 /* Path: <argv0_path> / <vpath> / Lib / LANDMARK */
 if (safe_wcscpy(prefix, argv0_path, prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 status = joinpath(prefix, vpath, prefix_len);
 PyMem_RawFree(vpath);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 status = joinpath(prefix, L"Lib", prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 status = joinpath(prefix, LANDMARK, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (ismodule(prefix, prefix_len)) {
 *found = -1;
 reduce(prefix);
 return _PyStatus_OK();
 }
 }
 }

 /* Search from argv0_path, until root is found */
 status = copy_absolute(prefix, argv0_path, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 do {
 /* Path: <argv0_path or substring> / <lib_python> / LANDMARK */
 size_t n = wcslen(prefix);
 status = joinpath(prefix, calculate->lib_python, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 status = joinpath(prefix, LANDMARK, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (ismodule(prefix, prefix_len)) {
 *found = 1;
 reduce(prefix);
 return _PyStatus_OK();
 }
 prefix[n] = L'0円';
 reduce(prefix);
 } while (prefix[0]);

 /* Look at configure's PREFIX.
 Path: <PREFIX macro> / <lib_python> / LANDMARK */
 if (safe_wcscpy(prefix, calculate->prefix, prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 status = joinpath(prefix, calculate->lib_python, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 status = joinpath(prefix, LANDMARK, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (ismodule(prefix, prefix_len)) {
 *found = 1;
 reduce(prefix);
 return _PyStatus_OK();
 }

 /* Fail */
 *found = 0;
 return _PyStatus_OK();
}


static PyStatus
calculate_prefix(PyCalculatePath *calculate, _PyPathConfig *pathconfig,
 const wchar_t *argv0_path,
 wchar_t *prefix, size_t prefix_len)
{
 PyStatus status;

 status = search_for_prefix(calculate, pathconfig, argv0_path,
 prefix, prefix_len,
 &calculate->prefix_found);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (!calculate->prefix_found) {
 if (calculate->warnings) {
 fprintf(stderr,
 "Could not find platform independent libraries <prefix>\n");
 }
 if (safe_wcscpy(prefix, calculate->prefix, prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 status = joinpath(prefix, calculate->lib_python, prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }
 return _PyStatus_OK();
}


static PyStatus
calculate_set_prefix(PyCalculatePath *calculate, _PyPathConfig *pathconfig,
 wchar_t *prefix)
{
 /* Reduce prefix and exec_prefix to their essence,
 * e.g. /usr/local/lib/python1.5 is reduced to /usr/local.
 * If we're loading relative to the build directory,
 * return the compiled-in defaults instead.
 */
 if (calculate->prefix_found > 0) {
 reduce(prefix);
 reduce(prefix);
 /* The prefix is the root directory, but reduce() chopped
 * off the "/". */
 if (!prefix[0]) {
 wcscpy(prefix, separator);
 }
 pathconfig->prefix = _PyMem_RawWcsdup(prefix);
 }
 else {
 pathconfig->prefix = _PyMem_RawWcsdup(calculate->prefix);
 }

 if (pathconfig->prefix == NULL) {
 return _PyStatus_NO_MEMORY();
 }
 return _PyStatus_OK();
}


static PyStatus
calculate_pybuilddir(const wchar_t *argv0_path,
 wchar_t *exec_prefix, size_t exec_prefix_len,
 int *found)
{
 PyStatus status;

 wchar_t filename[MAXPATHLEN+1];
 memset(filename, 0, sizeof(filename));
 size_t filename_len = Py_ARRAY_LENGTH(filename);

 /* Check to see if argv[0] is in the build directory. "pybuilddir.txt"
 is written by setup.py and contains the relative path to the location
 of shared library modules.

 Filename: <argv0_path> / "pybuilddir.txt" */
 if (safe_wcscpy(filename, argv0_path, filename_len) < 0) {
 return PATHLEN_ERR();
 }
 status = joinpath(filename, L"pybuilddir.txt", filename_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (!isfile(filename)) {
 return _PyStatus_OK();
 }

 FILE *fp = _Py_wfopen(filename, L"rb");
 if (fp == NULL) {
 errno = 0;
 return _PyStatus_OK();
 }

 char buf[MAXPATHLEN + 1];
 size_t n = fread(buf, 1, Py_ARRAY_LENGTH(buf) - 1, fp);
 buf[n] = '0円';
 fclose(fp);

 size_t dec_len;
 wchar_t *pybuilddir = _Py_DecodeUTF8_surrogateescape(buf, n, &dec_len);
 if (!pybuilddir) {
 return DECODE_LOCALE_ERR("pybuilddir.txt", dec_len);
 }

 /* Path: <argv0_path> / <pybuilddir content> */
 if (safe_wcscpy(exec_prefix, argv0_path, exec_prefix_len) < 0) {
 PyMem_RawFree(pybuilddir);
 return PATHLEN_ERR();
 }
 status = joinpath(exec_prefix, pybuilddir, exec_prefix_len);
 PyMem_RawFree(pybuilddir);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 *found = -1;
 return _PyStatus_OK();
}


/* search_for_exec_prefix requires that argv0_path be no more than
 MAXPATHLEN bytes long.
*/
static PyStatus
search_for_exec_prefix(PyCalculatePath *calculate, _PyPathConfig *pathconfig,
 const wchar_t *argv0_path,
 wchar_t *exec_prefix, size_t exec_prefix_len,
 int *found)
{
 PyStatus status;

 /* If PYTHONHOME is set, we believe it unconditionally */
 if (pathconfig->home) {
 /* Path: <home> / <lib_python> / "lib-dynload" */
 wchar_t *delim = wcschr(pathconfig->home, DELIM);
 if (delim) {
 if (safe_wcscpy(exec_prefix, delim+1, exec_prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 }
 else {
 if (safe_wcscpy(exec_prefix, pathconfig->home, exec_prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 }
 status = joinpath(exec_prefix, calculate->lib_python, exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 status = joinpath(exec_prefix, L"lib-dynload", exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 *found = 1;
 return _PyStatus_OK();
 }

 /* Check for pybuilddir.txt */
 assert(*found == 0);
 status = calculate_pybuilddir(argv0_path, exec_prefix, exec_prefix_len,
 found);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 if (*found) {
 return _PyStatus_OK();
 }

 /* Search from argv0_path, until root is found */
 status = copy_absolute(exec_prefix, argv0_path, exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 do {
 /* Path: <argv0_path or substring> / <lib_python> / "lib-dynload" */
 size_t n = wcslen(exec_prefix);
 status = joinpath(exec_prefix, calculate->lib_python, exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 status = joinpath(exec_prefix, L"lib-dynload", exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 if (isdir(exec_prefix)) {
 *found = 1;
 return _PyStatus_OK();
 }
 exec_prefix[n] = L'0円';
 reduce(exec_prefix);
 } while (exec_prefix[0]);

 /* Look at configure's EXEC_PREFIX.

 Path: <EXEC_PREFIX macro> / <lib_python> / "lib-dynload" */
 if (safe_wcscpy(exec_prefix, calculate->exec_prefix, exec_prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 status = joinpath(exec_prefix, calculate->lib_python, exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 status = joinpath(exec_prefix, L"lib-dynload", exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 if (isdir(exec_prefix)) {
 *found = 1;
 return _PyStatus_OK();
 }

 /* Fail */
 *found = 0;
 return _PyStatus_OK();
}


static PyStatus
calculate_exec_prefix(PyCalculatePath *calculate, _PyPathConfig *pathconfig,
 const wchar_t *argv0_path,
 wchar_t *exec_prefix, size_t exec_prefix_len)
{
 PyStatus status;

 status = search_for_exec_prefix(calculate, pathconfig, argv0_path,
 exec_prefix, exec_prefix_len,
 &calculate->exec_prefix_found);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (!calculate->exec_prefix_found) {
 if (calculate->warnings) {
 fprintf(stderr,
 "Could not find platform dependent libraries <exec_prefix>\n");
 }
 if (safe_wcscpy(exec_prefix, calculate->exec_prefix, exec_prefix_len) < 0) {
 return PATHLEN_ERR();
 }
 status = joinpath(exec_prefix, L"lib/lib-dynload", exec_prefix_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }
 /* If we found EXEC_PREFIX do *not* reduce it! (Yet.) */
 return _PyStatus_OK();
}


static PyStatus
calculate_set_exec_prefix(PyCalculatePath *calculate,
 _PyPathConfig *pathconfig,
 wchar_t *exec_prefix)
{
 if (calculate->exec_prefix_found > 0) {
 reduce(exec_prefix);
 reduce(exec_prefix);
 reduce(exec_prefix);
 if (!exec_prefix[0]) {
 wcscpy(exec_prefix, separator);
 }

 pathconfig->exec_prefix = _PyMem_RawWcsdup(exec_prefix);
 }
 else {
 pathconfig->exec_prefix = _PyMem_RawWcsdup(calculate->exec_prefix);
 }

 if (pathconfig->exec_prefix == NULL) {
 return _PyStatus_NO_MEMORY();
 }

 return _PyStatus_OK();
}


static PyStatus
calculate_program_full_path(PyCalculatePath *calculate, _PyPathConfig *pathconfig)
{
 PyStatus status;
 wchar_t program_full_path[MAXPATHLEN + 1];
 const size_t program_full_path_len = Py_ARRAY_LENGTH(program_full_path);
 memset(program_full_path, 0, sizeof(program_full_path));

#ifdef __APPLE__
 char execpath[MAXPATHLEN + 1];
 uint32_t nsexeclength = Py_ARRAY_LENGTH(execpath) - 1;
#endif

 /* If there is no slash in the argv0 path, then we have to
 * assume python is on the user's $PATH, since there's no
 * other way to find a directory to start the search from. If
 * $PATH isn't exported, you lose.
 */
 if (wcschr(pathconfig->program_name, SEP)) {
 if (safe_wcscpy(program_full_path, pathconfig->program_name,
 program_full_path_len) < 0) {
 return PATHLEN_ERR();
 }
 }
#ifdef __APPLE__
 /* On Mac OS X, if a script uses an interpreter of the form
 * "#!/opt/python2.3/bin/python", the kernel only passes "python"
 * as argv[0], which falls through to the $PATH search below.
 * If /opt/python2.3/bin isn't in your path, or is near the end,
 * this algorithm may incorrectly find /usr/bin/python. To work
 * around this, we can use _NSGetExecutablePath to get a better
 * hint of what the intended interpreter was, although this
 * will fail if a relative path was used. but in that case,
 * absolutize() should help us out below
 */
 else if(0 == _NSGetExecutablePath(execpath, &nsexeclength) &&
 execpath[0] == SEP)
 {
 size_t len;
 wchar_t *path = Py_DecodeLocale(execpath, &len);
 if (path == NULL) {
 return DECODE_LOCALE_ERR("executable path", len);
 }
 if (safe_wcscpy(program_full_path, path, program_full_path_len) < 0) {
 PyMem_RawFree(path);
 return PATHLEN_ERR();
 }
 PyMem_RawFree(path);
 }
#endif /* __APPLE__ */
 else if (calculate->path_env) {
 wchar_t *path = calculate->path_env;
 while (1) {
 wchar_t *delim = wcschr(path, DELIM);

 if (delim) {
 size_t len = delim - path;
 if (len >= program_full_path_len) {
 return PATHLEN_ERR();
 }
 wcsncpy(program_full_path, path, len);
 program_full_path[len] = '0円';
 }
 else {
 if (safe_wcscpy(program_full_path, path,
 program_full_path_len) < 0) {
 return PATHLEN_ERR();
 }
 }

 status = joinpath(program_full_path, pathconfig->program_name,
 program_full_path_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if (isxfile(program_full_path)) {
 break;
 }

 if (!delim) {
 program_full_path[0] = L'0円';
 break;
 }
 path = delim + 1;
 }
 }
 else {
 program_full_path[0] = '0円';
 }
 if (program_full_path[0] != SEP && program_full_path[0] != '0円') {
 status = absolutize(program_full_path, program_full_path_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }
#if defined(__CYGWIN__) || defined(__MINGW32__)
 /* For these platforms it is necessary to ensure that the .exe suffix
 * is appended to the filename, otherwise there is potential for
 * sys.executable to return the name of a directory under the same
 * path (bpo-28441).
 */
 if (program_full_path[0] != '0円') {
 status = add_exe_suffix(program_full_path, program_full_path_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }
#endif

 pathconfig->program_full_path = _PyMem_RawWcsdup(program_full_path);
 if (pathconfig->program_full_path == NULL) {
 return _PyStatus_NO_MEMORY();
 }
 return _PyStatus_OK();
}


static PyStatus
calculate_argv0_path(PyCalculatePath *calculate, const wchar_t *program_full_path,
 wchar_t *argv0_path, size_t argv0_path_len)
{
 if (safe_wcscpy(argv0_path, program_full_path, argv0_path_len) < 0) {
 return PATHLEN_ERR();
 }

#ifdef WITH_NEXT_FRAMEWORK
 NSModule pythonModule;

 /* On Mac OS X we have a special case if we're running from a framework.
 ** This is because the python home should be set relative to the library,
 ** which is in the framework, not relative to the executable, which may
 ** be outside of the framework. Except when we're in the build directory...
 */
 pythonModule = NSModuleForSymbol(NSLookupAndBindSymbol("_Py_Initialize"));
 /* Use dylib functions to find out where the framework was loaded from */
 const char* modPath = NSLibraryNameForModule(pythonModule);
 if (modPath != NULL) {
 /* We're in a framework. */
 /* See if we might be in the build directory. The framework in the
 ** build directory is incomplete, it only has the .dylib and a few
 ** needed symlinks, it doesn't have the Lib directories and such.
 ** If we're running with the framework from the build directory we must
 ** be running the interpreter in the build directory, so we use the
 ** build-directory-specific logic to find Lib and such.
 */
 PyStatus status;
 size_t len;
 wchar_t* wbuf = Py_DecodeLocale(modPath, &len);
 if (wbuf == NULL) {
 return DECODE_LOCALE_ERR("framework location", len);
 }

 if (safe_wcscpy(argv0_path, wbuf, argv0_path_len) < 0) {
 return PATHLEN_ERR();
 }
 reduce(argv0_path);
 status = joinpath(argv0_path, calculate->lib_python, argv0_path_len);
 if (_PyStatus_EXCEPTION(status)) {
 PyMem_RawFree(wbuf);
 return status;
 }
 status = joinpath(argv0_path, LANDMARK, argv0_path_len);
 if (_PyStatus_EXCEPTION(status)) {
 PyMem_RawFree(wbuf);
 return status;
 }
 if (!ismodule(argv0_path, Py_ARRAY_LENGTH(argv0_path))) {
 /* We are in the build directory so use the name of the
 executable - we know that the absolute path is passed */
 if (safe_wcscpy(argv0_path, program_full_path,
 argv0_path_len) < 0) {
 return PATHLEN_ERR();
 }
 }
 else {
 /* Use the location of the library as the program_full_path */
 if (safe_wcscpy(argv0_path, wbuf, argv0_path_len) < 0) {
 return PATHLEN_ERR();
 }
 }
 PyMem_RawFree(wbuf);
 }
#endif

#if HAVE_READLINK
 wchar_t tmpbuffer[MAXPATHLEN + 1];
 const size_t buflen = Py_ARRAY_LENGTH(tmpbuffer);
 int linklen = _Py_wreadlink(program_full_path, tmpbuffer, buflen);
 while (linklen != -1) {
 if (tmpbuffer[0] == SEP) {
 /* tmpbuffer should never be longer than MAXPATHLEN,
 but extra check does not hurt */
 if (safe_wcscpy(argv0_path, tmpbuffer, argv0_path_len) < 0) {
 return PATHLEN_ERR();
 }
 }
 else {
 /* Interpret relative to program_full_path */
 PyStatus status;
 reduce(argv0_path);
 status = joinpath(argv0_path, tmpbuffer, argv0_path_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }
 linklen = _Py_wreadlink(argv0_path, tmpbuffer, buflen);
 }
#endif /* HAVE_READLINK */

 reduce(argv0_path);
 /* At this point, argv0_path is guaranteed to be less than
 MAXPATHLEN bytes long. */
 return _PyStatus_OK();
}


/* Search for an "pyvenv.cfg" environment configuration file, first in the
 executable's directory and then in the parent directory.
 If found, open it for use when searching for prefixes.
*/
static PyStatus
calculate_read_pyenv(PyCalculatePath *calculate,
 wchar_t *argv0_path, size_t argv0_path_len)
{
 PyStatus status;
 const wchar_t *env_cfg = L"pyvenv.cfg";
 FILE *env_file;

 wchar_t filename[MAXPATHLEN+1];
 const size_t filename_len = Py_ARRAY_LENGTH(filename);
 memset(filename, 0, sizeof(filename));

 /* Filename: <argv0_path_len> / "pyvenv.cfg" */
 if (safe_wcscpy(filename, argv0_path, filename_len) < 0) {
 return PATHLEN_ERR();
 }

 status = joinpath(filename, env_cfg, filename_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 env_file = _Py_wfopen(filename, L"r");
 if (env_file == NULL) {
 errno = 0;

 /* Filename: <basename(basename(argv0_path_len))> / "pyvenv.cfg" */
 reduce(filename);
 reduce(filename);
 status = joinpath(filename, env_cfg, filename_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 env_file = _Py_wfopen(filename, L"r");
 if (env_file == NULL) {
 errno = 0;
 return _PyStatus_OK();
 }
 }

 /* Look for a 'home' variable and set argv0_path to it, if found */
 wchar_t home[MAXPATHLEN+1];
 memset(home, 0, sizeof(home));

 if (_Py_FindEnvConfigValue(env_file, L"home",
 home, Py_ARRAY_LENGTH(home))) {
 if (safe_wcscpy(argv0_path, home, argv0_path_len) < 0) {
 fclose(env_file);
 return PATHLEN_ERR();
 }
 }
 fclose(env_file);
 return _PyStatus_OK();
}


static PyStatus
calculate_zip_path(PyCalculatePath *calculate, const wchar_t *prefix,
 wchar_t *zip_path, size_t zip_path_len)
{
 PyStatus status;

 if (calculate->prefix_found > 0) {
 /* Use the reduced prefix returned by Py_GetPrefix() */
 if (safe_wcscpy(zip_path, prefix, zip_path_len) < 0) {
 return PATHLEN_ERR();
 }
 reduce(zip_path);
 reduce(zip_path);
 }
 else {
 if (safe_wcscpy(zip_path, calculate->prefix, zip_path_len) < 0) {
 return PATHLEN_ERR();
 }
 }
 //cxunmz
 status = joinpath(zip_path, L"lib/python3.8", zip_path_len);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 /* Replace "00" with version */
 // size_t bufsz = wcslen(zip_path);
 // zip_path[bufsz - 2] = VERSION[0];
 // zip_path[bufsz - 1] = VERSION[2];
 return _PyStatus_OK();
}


static PyStatus
calculate_module_search_path(PyCalculatePath *calculate,
 _PyPathConfig *pathconfig,
 const wchar_t *prefix,
 const wchar_t *exec_prefix,
 const wchar_t *zip_path)
{
 /* Calculate size of return buffer */
 size_t bufsz = 0;
 if (calculate->pythonpath_env != NULL) {
 bufsz += wcslen(calculate->pythonpath_env) + 1;
 }

 wchar_t *defpath = calculate->pythonpath;
 size_t prefixsz = wcslen(prefix) + 1;
 while (1) {
 wchar_t *delim = wcschr(defpath, DELIM);

 if (defpath[0] != SEP) {
 /* Paths are relative to prefix */
 bufsz += prefixsz;
 }

 if (delim) {
 bufsz += delim - defpath + 1;
 }
 else {
 bufsz += wcslen(defpath) + 1;
 break;
 }
 defpath = delim + 1;
 }

 bufsz += wcslen(zip_path) + 1;
 bufsz += wcslen(exec_prefix) + 1;

 /* Allocate the buffer */
 wchar_t *buf = PyMem_RawMalloc(bufsz * sizeof(wchar_t));
 if (buf == NULL) {
 return _PyStatus_NO_MEMORY();
 }
 buf[0] = '0円';

 /* Run-time value of $PYTHONPATH goes first */
 if (calculate->pythonpath_env) {
 wcscpy(buf, calculate->pythonpath_env);
 wcscat(buf, delimiter);
 }

 /* Next is the default zip path */
 wcscat(buf, zip_path);
 wcscat(buf, delimiter);

 /* Next goes merge of compile-time $PYTHONPATH with
 * dynamically located prefix.
 */
 defpath = calculate->pythonpath;
 while (1) {
 wchar_t *delim = wcschr(defpath, DELIM);

 if (defpath[0] != SEP) {
 wcscat(buf, prefix);
 if (prefixsz >= 2 && prefix[prefixsz - 2] != SEP &&
 defpath[0] != (delim ? DELIM : L'0円'))
 {
 /* not empty */
 wcscat(buf, separator);
 }
 }

 if (delim) {
 size_t len = delim - defpath + 1;
 size_t end = wcslen(buf) + len;
 wcsncat(buf, defpath, len);
 buf[end] = '0円';
 }
 else {
 wcscat(buf, defpath);
 break;
 }
 defpath = delim + 1;
 }
 wcscat(buf, delimiter);

 /* Finally, on goes the directory for dynamic-load modules */
 wcscat(buf, exec_prefix);

 pathconfig->module_search_path = buf;
 return _PyStatus_OK();
}


static PyStatus
calculate_init(PyCalculatePath *calculate, const PyConfig *config)
{
 size_t len;
 const char *path = getenv("PATH");
 if (path) {
 calculate->path_env = Py_DecodeLocale(path, &len);
 if (!calculate->path_env) {
 return DECODE_LOCALE_ERR("PATH environment variable", len);
 }
 }

 calculate->pythonpath = Py_DecodeLocale(PYTHONPATH, &len);
 if (!calculate->pythonpath) {
 return DECODE_LOCALE_ERR("PYTHONPATH define", len);
 }

 calculate->prefix = Py_DecodeLocale(PREFIX, &len);
 if (!calculate->prefix) {
 return DECODE_LOCALE_ERR("PREFIX define", len);
 }
 calculate->exec_prefix = Py_DecodeLocale(EXEC_PREFIX, &len);
 if (!calculate->exec_prefix) {
 return DECODE_LOCALE_ERR("EXEC_PREFIX define", len);
 }
 calculate->lib_python = Py_DecodeLocale("lib/python" VERSION, &len);
 if (!calculate->lib_python) {
 return DECODE_LOCALE_ERR("EXEC_PREFIX define", len);
 }

 calculate->warnings = config->pathconfig_warnings;
 calculate->pythonpath_env = config->pythonpath_env;

 return _PyStatus_OK();
}


static void
calculate_free(PyCalculatePath *calculate)
{
 PyMem_RawFree(calculate->pythonpath);
 PyMem_RawFree(calculate->prefix);
 PyMem_RawFree(calculate->exec_prefix);
 PyMem_RawFree(calculate->lib_python);
 PyMem_RawFree(calculate->path_env);
}


static PyStatus
calculate_path(PyCalculatePath *calculate, _PyPathConfig *pathconfig)
{
 PyStatus status;

 if (pathconfig->program_full_path == NULL) {
 status = calculate_program_full_path(calculate, pathconfig);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }

 wchar_t argv0_path[MAXPATHLEN+1];
 memset(argv0_path, 0, sizeof(argv0_path));

 status = calculate_argv0_path(calculate, pathconfig->program_full_path,
 argv0_path, Py_ARRAY_LENGTH(argv0_path));
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 /* If a pyvenv.cfg configure file is found,
 argv0_path is overriden with its 'home' variable. */
 status = calculate_read_pyenv(calculate,
 argv0_path, Py_ARRAY_LENGTH(argv0_path));
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 wchar_t prefix[MAXPATHLEN+1];
 memset(prefix, 0, sizeof(prefix));
 status = calculate_prefix(calculate, pathconfig,
 argv0_path,
 prefix, Py_ARRAY_LENGTH(prefix));
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 wchar_t zip_path[MAXPATHLEN+1]; /* ".../lib/pythonXY.zip" */
 memset(zip_path, 0, sizeof(zip_path));

 status = calculate_zip_path(calculate, prefix,
 zip_path, Py_ARRAY_LENGTH(zip_path));
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 wchar_t exec_prefix[MAXPATHLEN+1];
 memset(exec_prefix, 0, sizeof(exec_prefix));
 status = calculate_exec_prefix(calculate, pathconfig, argv0_path,
 exec_prefix, Py_ARRAY_LENGTH(exec_prefix));
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }

 if ((!calculate->prefix_found || !calculate->exec_prefix_found) &&
 calculate->warnings)
 {
 fprintf(stderr,
 "Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]\n");
 }

 if (pathconfig->module_search_path == NULL) {
 status = calculate_module_search_path(calculate, pathconfig,
 prefix, exec_prefix, zip_path);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }

 if (pathconfig->prefix == NULL) {
 status = calculate_set_prefix(calculate, pathconfig, prefix);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }

 if (pathconfig->exec_prefix == NULL) {
 status = calculate_set_exec_prefix(calculate, pathconfig, exec_prefix);
 if (_PyStatus_EXCEPTION(status)) {
 return status;
 }
 }

 return _PyStatus_OK();
}


/* Calculate the Python path configuration.

 Inputs:

 - PATH environment variable
 - Macros: PYTHONPATH, PREFIX, EXEC_PREFIX, VERSION (ex: "3.9").
 PREFIX and EXEC_PREFIX are generated by the configure script.
 PYTHONPATH macro is the default search path.
 - pybuilddir.txt file
 - pyvenv.cfg configuration file
 - PyConfig fields ('config' function argument):

 - pathconfig_warnings
 - pythonpath_env (PYTHONPATH environment variable)

 - _PyPathConfig fields ('pathconfig' function argument):

 - program_name: see config_init_program_name()
 - home: Py_SetPythonHome() or PYTHONHOME environment variable

 - current working directory: see copy_absolute()

 Outputs, 'pathconfig' fields:

 - program_full_path
 - module_search_path
 - prefix
 - exec_prefix

 If a field is already set (non NULL), it is left unchanged. */
PyStatus
_PyPathConfig_Calculate(_PyPathConfig *pathconfig, const PyConfig *config)
{
 PyStatus status;
 PyCalculatePath calculate;
 memset(&calculate, 0, sizeof(calculate));

 status = calculate_init(&calculate, config);
 if (_PyStatus_EXCEPTION(status)) {
 goto done;
 }

 status = calculate_path(&calculate, pathconfig);
 if (_PyStatus_EXCEPTION(status)) {
 goto done;
 }

 status = _PyStatus_OK();

done:
 calculate_free(&calculate);
 return status;
}

#ifdef __cplusplus
}
#endif