/* Return the initial module search path. */

#include "Python.h"

#include "osdefs.h"

#include <sys/types.h>

#include <sys/stat.h>

#include <string.h>

#if HAVE_UNISTD_H

#include <unistd.h>

#endif /* HAVE_UNISTD_H */

#ifdef WITH_NEXT_FRAMEWORK

#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 slashs 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

* Modules/Setup. 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.

*/

#ifndef VERSION

#define VERSION "2.0"

#endif

#ifndef VPATH

#define VPATH "."

#endif

#ifndef PREFIX

#define PREFIX "/usr/local"

#endif

#ifndef EXEC_PREFIX

#define EXEC_PREFIX PREFIX

#endif

#ifndef PYTHONPATH

/* I know this isn't K&R C, but the Makefile specifies it anyway */

#define PYTHONPATH PREFIX "/lib/python" VERSION ":" \

EXEC_PREFIX "/lib/python" VERSION "/lib-dynload"

#endif

#ifndef LANDMARK

#define LANDMARK "os.py"

#endif

static char prefix[MAXPATHLEN+1];

static char exec_prefix[MAXPATHLEN+1];

static char progpath[MAXPATHLEN+1];

static char *module_search_path = NULL;

static char lib_python[] = "lib/python" VERSION;

static void

reduce(char *dir)

{

size_t i = strlen(dir);

while (i > 0 && dir[i] != SEP)

--i;

dir[i] = '\0';

}

#ifndef S_ISREG

#define S_ISREG(x) (((x) & S_IFMT) == S_IFREG)

#endif

#ifndef S_ISDIR

#define S_ISDIR(x) (((x) & S_IFMT) == S_IFDIR)

#endif

static int

isfile(char *filename) /* Is file, not directory */

{

struct stat buf;

if (stat(filename, &buf) != 0)

return 0;

if (!S_ISREG(buf.st_mode))

return 0;

return 1;

}

static int

ismodule(char *filename) /* Is module -- check for .pyc/.pyo too */

{

if (isfile(filename))

return 1;

/* Check for the compiled version of prefix. */

if (strlen(filename) < MAXPATHLEN) {

strcat(filename, Py_OptimizeFlag ? "o" : "c");

if (isfile(filename))

return 1;

}

return 0;

}

static int

isxfile(char *filename) /* Is executable file */

{

struct stat buf;

if (stat(filename, &buf) != 0)

return 0;

if (!S_ISREG(buf.st_mode))

return 0;

if ((buf.st_mode & 0111) == 0)

return 0;

return 1;

}

static int

isdir(char *filename) /* Is directory */

{

struct stat buf;

if (stat(filename, &buf) != 0)

return 0;

if (!S_ISDIR(buf.st_mode))

return 0;

return 1;

}

/* joinpath requires that any buffer argument passed to it has at

least MAXPATHLEN + 1 bytes allocated. If this requirement is met,

it guarantees that it will never overflow the buffer. If stuff

is too long, buffer will contain a truncated copy of stuff.

*/

static void

joinpath(char *buffer, char *stuff)

{

size_t n, k;

if (stuff[0] == SEP)

n = 0;

else {

n = strlen(buffer);

if (n > 0 && buffer[n-1] != SEP && n < MAXPATHLEN)

buffer[n++] = SEP;

}

k = strlen(stuff);

if (n + k > MAXPATHLEN)

k = MAXPATHLEN - n;

strncpy(buffer+n, stuff, k);

buffer[n+k] = '\0';

}

/* init_path_from_argv0 requirs that path be allocated at least

MAXPATHLEN + 1 bytes and that argv0_path be no more than MAXPATHLEN

bytes.

*/

static void

init_path_from_argv0(char *path, char *argv0_path)

{

if (argv0_path[0] == '/')

strcpy(path, argv0_path);

else if (argv0_path[0] == '.') {

getcwd(path, MAXPATHLEN);

if (argv0_path[1] == '/')

joinpath(path, argv0_path + 2);

else

joinpath(path, argv0_path);

}

else {

getcwd(path, MAXPATHLEN);

joinpath(path, argv0_path);

}

}

/* search_for_prefix requires that argv0_path be no more than MAXPATHLEN

bytes long.

*/

static int

search_for_prefix(char *argv0_path, char *home)

{

size_t n;

char *vpath;

/* If PYTHONHOME is set, we believe it unconditionally */

if (home) {

char *delim;

strncpy(prefix, home, MAXPATHLEN);

delim = strchr(prefix, DELIM);

if (delim)

*delim = '\0';

joinpath(prefix, lib_python);

joinpath(prefix, LANDMARK);

return 1;

}

/* Check to see if argv[0] is in the build directory */

strcpy(prefix, argv0_path);

joinpath(prefix, "Modules/Setup");

if (isfile(prefix)) {

/* Check VPATH to see if argv0_path is in the build directory.

* Complication: the VPATH passed in is relative to the

* Modules build directory and points to the Modules source

* directory; we need it relative to the build tree and

* pointing to the source tree. Solution: chop off a leading

* ".." (but only if it's there -- it could be an absolute

* path) and chop off the final component (assuming it's

* "Modules").

*/

vpath = VPATH;

if (vpath[0] == '.' && vpath[1] == '.' && vpath[2] == '/')

vpath += 3;

strcpy(prefix, argv0_path);

joinpath(prefix, vpath);

reduce(prefix);

joinpath(prefix, "Lib");

joinpath(prefix, LANDMARK);

if (ismodule(prefix))

return -1;

}

/* Search from argv0_path, until root is found */

init_path_from_argv0(prefix, argv0_path);

do {

n = strlen(prefix);

joinpath(prefix, lib_python);

joinpath(prefix, LANDMARK);

if (ismodule(prefix))

return 1;

prefix[n] = '\0';

reduce(prefix);

} while (prefix[0]);

/* Look at configure's PREFIX */

strncpy(prefix, PREFIX, MAXPATHLEN);

joinpath(prefix, lib_python);

joinpath(prefix, LANDMARK);

if (ismodule(prefix))

return 1;

/* Fail */

return 0;

}

/* search_for_exec_prefix requires that argv0_path be no more than

MAXPATHLEN bytes long.

*/

static int

search_for_exec_prefix(char *argv0_path, char *home)

{

size_t n;

/* If PYTHONHOME is set, we believe it unconditionally */

if (home) {

char *delim;

delim = strchr(home, DELIM);

if (delim)

strncpy(exec_prefix, delim+1, MAXPATHLEN);

else

strncpy(exec_prefix, home, MAXPATHLEN);

joinpath(exec_prefix, lib_python);

joinpath(exec_prefix, "lib-dynload");

return 1;

}

/* Check to see if argv[0] is in the build directory */

strcpy(exec_prefix, argv0_path);

joinpath(exec_prefix, "Modules/Setup");

if (isfile(exec_prefix)) {

reduce(exec_prefix);

return -1;

}

/* Search from argv0_path, until root is found */

init_path_from_argv0(exec_prefix, argv0_path);

do {

n = strlen(exec_prefix);

joinpath(exec_prefix, lib_python);

joinpath(exec_prefix, "lib-dynload");

if (isdir(exec_prefix))

return 1;

exec_prefix[n] = '\0';

reduce(exec_prefix);

} while (exec_prefix[0]);

/* Look at configure's EXEC_PREFIX */

strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);

joinpath(exec_prefix, lib_python);

joinpath(exec_prefix, "lib-dynload");

if (isdir(exec_prefix))

return 1;

/* Fail */

return 0;

}

static void

calculate_path(void)

{

extern char *Py_GetProgramName(void);

static char delimiter[2] = {DELIM, '\0'};

static char separator[2] = {SEP, '\0'};

char *pythonpath = PYTHONPATH;

char *rtpypath = getenv("PYTHONPATH");

char *home = Py_GetPythonHome();

char *path = getenv("PATH");

char *prog = Py_GetProgramName();

char argv0_path[MAXPATHLEN+1];

int pfound, efound; /* 1 if found; -1 if found build directory */

char *buf;

size_t bufsz;

size_t prefixsz;

char *defpath = pythonpath;

#ifdef WITH_NEXT_FRAMEWORK

NSModule pythonModule;

#endif

#ifdef WITH_NEXT_FRAMEWORK

/* XXX Need to check this code for buffer overflows */

pythonModule = NSModuleForSymbol(NSLookupAndBindSymbol("_Py_Initialize"));

/* Use dylib functions to find out where the framework was loaded from */

buf = NSLibraryNameForModule(pythonModule);

if (buf != NULL) {

/* We're in a framework. */

strcpy(progpath, buf);

/* Frameworks have support for versioning */

strcpy(lib_python, "lib");

}

else {

/* If we're not in a framework, fall back to the old way

(even though NSNameOfModule() probably does the same thing.) */

#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 (strchr(prog, SEP))

strncpy(progpath, prog, MAXPATHLEN);

else if (path) {

int bufspace = MAXPATHLEN;

while (1) {

char *delim = strchr(path, DELIM);

if (delim) {

size_t len = delim - path;

if (len > bufspace)

len = bufspace;

strncpy(progpath, path, len);

*(progpath + len) = '\0';

bufspace -= len;

}

else

strncpy(progpath, path, bufspace);

joinpath(progpath, prog);

if (isxfile(progpath))

break;

if (!delim) {

progpath[0] = '\0';

break;

}

path = delim + 1;

}

}

else

progpath[0] = '\0';

#ifdef WITH_NEXT_FRAMEWORK

}

#endif

strncpy(argv0_path, progpath, MAXPATHLEN);

#if HAVE_READLINK

{

char tmpbuffer[MAXPATHLEN+1];

int linklen = readlink(progpath, tmpbuffer, MAXPATHLEN);

while (linklen != -1) {

/* It's not null terminated! */

tmpbuffer[linklen] = '\0';

if (tmpbuffer[0] == SEP)

/* tmpbuffer should never be longer than MAXPATHLEN,

but extra check does not hurt */

strncpy(argv0_path, tmpbuffer, MAXPATHLEN);

else {

/* Interpret relative to progpath */

reduce(argv0_path);

joinpath(argv0_path, tmpbuffer);

}

linklen = readlink(argv0_path, tmpbuffer, MAXPATHLEN);

}

}

#endif /* HAVE_READLINK */

reduce(argv0_path);

/* At this point, argv0_path is guaranteed to be less than

MAXPATHLEN bytes long.

*/

if (!(pfound = search_for_prefix(argv0_path, home))) {

if (!Py_FrozenFlag)

fprintf(stderr,

"Could not find platform independent libraries <prefix>\n");

strncpy(prefix, PREFIX, MAXPATHLEN);

joinpath(prefix, lib_python);

}

else

reduce(prefix);

if (!(efound = search_for_exec_prefix(argv0_path, home))) {

if (!Py_FrozenFlag)

fprintf(stderr,

"Could not find platform dependent libraries <exec_prefix>\n");

strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);

joinpath(exec_prefix, "lib/lib-dynload");

}

/* If we found EXEC_PREFIX do *not* reduce it! (Yet.) */

if ((!pfound || !efound) && !Py_FrozenFlag)

fprintf(stderr,

"Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]\n");

/* Calculate size of return buffer.

*/

bufsz = 0;

if (rtpypath)

bufsz += strlen(rtpypath) + 1;

prefixsz = strlen(prefix) + 1;

while (1) {

char *delim = strchr(defpath, DELIM);

if (defpath[0] != SEP)

/* Paths are relative to prefix */

bufsz += prefixsz;

if (delim)

bufsz += delim - defpath + 1;

else {

bufsz += strlen(defpath) + 1;

break;

}

defpath = delim + 1;

}

bufsz += strlen(exec_prefix) + 1;

/* This is the only malloc call in this file */

buf = PyMem_Malloc(bufsz);

if (buf == NULL) {

/* We can't exit, so print a warning and limp along */

fprintf(stderr, "Not enough memory for dynamic PYTHONPATH.\n");

fprintf(stderr, "Using default static PYTHONPATH.\n");

module_search_path = PYTHONPATH;

}

else {

/* Run-time value of $PYTHONPATH goes first */

if (rtpypath) {

strcpy(buf, rtpypath);

strcat(buf, delimiter);

}

else

buf[0] = '\0';

/* Next goes merge of compile-time $PYTHONPATH with

* dynamically located prefix.

*/

defpath = pythonpath;

while (1) {

char *delim = strchr(defpath, DELIM);

if (defpath[0] != SEP) {

strcat(buf, prefix);

strcat(buf, separator);

}

if (delim) {

size_t len = delim - defpath + 1;

size_t end = strlen(buf) + len;

strncat(buf, defpath, len);

*(buf + end) = '\0';

}

else {

strcat(buf, defpath);

break;

}

defpath = delim + 1;

}

strcat(buf, delimiter);

/* Finally, on goes the directory for dynamic-load modules */

strcat(buf, exec_prefix);

/* And publish the results */

module_search_path = buf;

}

/* 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 (pfound > 0) {

reduce(prefix);

reduce(prefix);

}

else

strncpy(prefix, PREFIX, MAXPATHLEN);

if (efound > 0) {

reduce(exec_prefix);

reduce(exec_prefix);

reduce(exec_prefix);

}

else

strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);

}

/* External interface */

char *

Py_GetPath(void)

{

if (!module_search_path)

calculate_path();

return module_search_path;

}

char *

Py_GetPrefix(void)

{

if (!module_search_path)

calculate_path();

return prefix;

}

char *

Py_GetExecPrefix(void)

{

if (!module_search_path)

calculate_path();

return exec_prefix;

}

char *

Py_GetProgramFullPath(void)

{

if (!module_search_path)

calculate_path();

return progpath;

}