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cpython/Modules/getpath.c

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/* 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 "2.1"
#endif
#ifndef VPATH
#define VPATH "."
#endif
#ifndef PREFIX
#define PREFIX "/usr/local"
#endif
#ifndef EXEC_PREFIX
#define EXEC_PREFIX PREFIX
#endif
#ifndef PYTHONPATH
#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 requires 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. */
vpath = VPATH;
strcpy(prefix, argv0_path);
joinpath(prefix, vpath);
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 = Py_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;
}
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