Modules/getpath.c

   1 /* Return the initial module search path. */
   2
   3 #include "Python.h"
   4 #include "osdefs.h"
   5
   6 #include <sys/types.h>
   7 #include <string.h>
   8
   9 #ifdef WITH_NEXT_FRAMEWORK
  10 #include <mach-o/dyld.h>
  11 #endif
  12
  13 /* Search in some common locations for the associated Python libraries.
  14  *
  15  * Two directories must be found, the platform independent directory
  16  * (prefix), containing the common .py and .pyc files, and the platform
  17  * dependent directory (exec_prefix), containing the shared library
  18  * modules.  Note that prefix and exec_prefix can be the same directory,
  19  * but for some installations, they are different.
  20  *
  21  * Py_GetPath() carries out separate searches for prefix and exec_prefix.
  22  * Each search tries a number of different locations until a ``landmark''
  23  * file or directory is found.  If no prefix or exec_prefix is found, a
  24  * warning message is issued and the preprocessor defined PREFIX and
  25  * EXEC_PREFIX are used (even though they will not work); python carries on
  26  * as best as is possible, but most imports will fail.
  27  *
  28  * Before any searches are done, the location of the executable is
  29  * determined.  If argv[0] has one or more slashs in it, it is used
  30  * unchanged.  Otherwise, it must have been invoked from the shell's path,
  31  * so we search $PATH for the named executable and use that.  If the
  32  * executable was not found on $PATH (or there was no $PATH environment
  33  * variable), the original argv[0] string is used.
  34  *
  35  * Next, the executable location is examined to see if it is a symbolic
  36  * link.  If so, the link is chased (correctly interpreting a relative
  37  * pathname if one is found) and the directory of the link target is used.
  38  *
  39  * Finally, argv0_path is set to the directory containing the executable
  40  * (i.e. the last component is stripped).
  41  *
  42  * With argv0_path in hand, we perform a number of steps.  The same steps
  43  * are performed for prefix and for exec_prefix, but with a different
  44  * landmark.
  45  *
  46  * Step 1. Are we running python out of the build directory?  This is
  47  * checked by looking for a different kind of landmark relative to
  48  * argv0_path.  For prefix, the landmark's path is derived from the VPATH
  49  * preprocessor variable (taking into account that its value is almost, but
  50  * not quite, what we need).  For exec_prefix, the landmark is
  51  * Modules/Setup.  If the landmark is found, we're done.
  52  *
  53  * For the remaining steps, the prefix landmark will always be
  54  * lib/python$VERSION/os.py and the exec_prefix will always be
  55  * lib/python$VERSION/lib-dynload, where $VERSION is Python's version
  56  * number as supplied by the Makefile.  Note that this means that no more
  57  * build directory checking is performed; if the first step did not find
  58  * the landmarks, the assumption is that python is running from an
  59  * installed setup.
  60  *
  61  * Step 2. See if the $PYTHONHOME environment variable points to the
  62  * installed location of the Python libraries.  If $PYTHONHOME is set, then
  63  * it points to prefix and exec_prefix.  $PYTHONHOME can be a single
  64  * directory, which is used for both, or the prefix and exec_prefix
  65  * directories separated by a colon.
  66  *
  67  * Step 3. Try to find prefix and exec_prefix relative to argv0_path,
  68  * backtracking up the path until it is exhausted.  This is the most common
  69  * step to succeed.  Note that if prefix and exec_prefix are different,
  70  * exec_prefix is more likely to be found; however if exec_prefix is a
  71  * subdirectory of prefix, both will be found.
  72  *
  73  * Step 4. Search the directories pointed to by the preprocessor variables
  74  * PREFIX and EXEC_PREFIX.  These are supplied by the Makefile but can be
  75  * passed in as options to the configure script.
  76  *
  77  * That's it!
  78  *
  79  * Well, almost.  Once we have determined prefix and exec_prefix, the
  80  * preprocessor variable PYTHONPATH is used to construct a path.  Each
  81  * relative path on PYTHONPATH is prefixed with prefix.  Then the directory
  82  * containing the shared library modules is appended.  The environment
  83  * variable $PYTHONPATH is inserted in front of it all.  Finally, the
  84  * prefix and exec_prefix globals are tweaked so they reflect the values
  85  * expected by other code, by stripping the "lib/python$VERSION/..." stuff
  86  * off.  If either points to the build directory, the globals are reset to
  87  * the corresponding preprocessor variables (so sys.prefix will reflect the
  88  * installation location, even though sys.path points into the build
  89  * directory).  This seems to make more sense given that currently the only
  90  * known use of sys.prefix and sys.exec_prefix is for the ILU installation
  91  * process to find the installed Python tree.
  92  */
  93
  94 #ifndef VERSION
  95 #if defined(__VMS)
  96 #define VERSION "2_1"
  97 #else
  98 #define VERSION "2.1"
  99 #endif
 100 #endif
 101
 102 #ifndef VPATH
 103 #define VPATH "."
 104 #endif
 105
 106 #ifndef PREFIX
 107 #define PREFIX "/usr/local"
 108 #endif
 109
 110 #ifndef EXEC_PREFIX
 111 #define EXEC_PREFIX PREFIX
 112 #endif
 113
 114 #ifndef PYTHONPATH
 115 #define PYTHONPATH PREFIX "/lib/python" VERSION ":" \
 116               EXEC_PREFIX "/lib/python" VERSION "/lib-dynload"
 117 #endif
 118
 119 #ifndef LANDMARK
 120 #define LANDMARK "os.py"
 121 #endif
 122
 123 static char prefix[MAXPATHLEN+1];
 124 static char exec_prefix[MAXPATHLEN+1];
 125 static char progpath[MAXPATHLEN+1];
 126 static char *module_search_path = NULL;
 127 static char lib_python[] = "lib/python" VERSION;
 128
 129 static void
 130 reduce(char *dir)
 131 {
 132     size_t i = strlen(dir);
 133     while (i > 0 && dir[i] != SEP)
 134         --i;
 135     dir[i] = '\0';
 136 }
 137
 138
 139 static int
 140 isfile(char *filename)          /* Is file, not directory */
 141 {
 142     struct stat buf;
 143     if (stat(filename, &buf) != 0)
 144         return 0;
 145     if (!S_ISREG(buf.st_mode))
 146         return 0;
 147     return 1;
 148 }
 149
 150
 151 static int
 152 ismodule(char *filename)        /* Is module -- check for .pyc/.pyo too */
 153 {
 154     if (isfile(filename))
 155         return 1;
 156
 157     /* Check for the compiled version of prefix. */
 158     if (strlen(filename) < MAXPATHLEN) {
 159         strcat(filename, Py_OptimizeFlag ? "o" : "c");
 160         if (isfile(filename))
 161             return 1;
 162     }
 163     return 0;
 164 }
 165
 166
 167 static int
 168 isxfile(char *filename)         /* Is executable file */
 169 {
 170     struct stat buf;
 171     if (stat(filename, &buf) != 0)
 172         return 0;
 173     if (!S_ISREG(buf.st_mode))
 174         return 0;
 175     if ((buf.st_mode & 0111) == 0)
 176         return 0;
 177     return 1;
 178 }
 179
 180
 181 static int
 182 isdir(char *filename)                   /* Is directory */
 183 {
 184     struct stat buf;
 185     if (stat(filename, &buf) != 0)
 186         return 0;
 187     if (!S_ISDIR(buf.st_mode))
 188         return 0;
 189     return 1;
 190 }
 191
 192
 193 /* joinpath requires that any buffer argument passed to it has at
 194    least MAXPATHLEN + 1 bytes allocated.  If this requirement is met,
 195    it guarantees that it will never overflow the buffer.  If stuff
 196    is too long, buffer will contain a truncated copy of stuff.
 197 */
 198 static void
 199 joinpath(char *buffer, char *stuff)
 200 {
 201     size_t n, k;
 202     if (stuff[0] == SEP)
 203         n = 0;
 204     else {
 205         n = strlen(buffer);
 206         if (n > 0 && buffer[n-1] != SEP && n < MAXPATHLEN)
 207             buffer[n++] = SEP;
 208     }
 209     k = strlen(stuff);
 210     if (n + k > MAXPATHLEN)
 211         k = MAXPATHLEN - n;
 212     strncpy(buffer+n, stuff, k);
 213     buffer[n+k] = '\0';
 214 }
 215
 216 /* copy_absolute requires that path be allocated at least
 217    MAXPATHLEN + 1 bytes and that p be no more than MAXPATHLEN bytes. */
 218 static void
 219 copy_absolute(char *path, char *p)
 220 {
 221     if (p[0] == SEP)
 222         strcpy(path, p);
 223     else {
 224         getcwd(path, MAXPATHLEN);
 225         if (p[0] == '.' && p[1] == SEP)
 226             p += 2;
 227         joinpath(path, p);
 228     }
 229 }
 230
 231 /* absolutize() requires that path be allocated at least MAXPATHLEN+1 bytes. */
 232 static void
 233 absolutize(char *path)
 234 {
 235     char buffer[MAXPATHLEN + 1];
 236
 237     if (path[0] == SEP)
 238         return;
 239     copy_absolute(buffer, path);
 240     strcpy(path, buffer);
 241 }
 242
 243 /* search_for_prefix requires that argv0_path be no more than MAXPATHLEN
 244    bytes long.
 245 */
 246 static int
 247 search_for_prefix(char *argv0_path, char *home)
 248 {
 249     size_t n;
 250     char *vpath;
 251
 252     /* If PYTHONHOME is set, we believe it unconditionally */
 253     if (home) {
 254         char *delim;
 255         strncpy(prefix, home, MAXPATHLEN);
 256         delim = strchr(prefix, DELIM);
 257         if (delim)
 258             *delim = '\0';
 259         joinpath(prefix, lib_python);
 260         joinpath(prefix, LANDMARK);
 261         return 1;
 262     }
 263
 264     /* Check to see if argv[0] is in the build directory */
 265     strcpy(prefix, argv0_path);
 266     joinpath(prefix, "Modules/Setup");
 267     if (isfile(prefix)) {
 268         /* Check VPATH to see if argv0_path is in the build directory. */
 269         vpath = VPATH;
 270         strcpy(prefix, argv0_path);
 271         joinpath(prefix, vpath);
 272         joinpath(prefix, "Lib");
 273         joinpath(prefix, LANDMARK);
 274         if (ismodule(prefix))
 275             return -1;
 276     }
 277
 278     /* Search from argv0_path, until root is found */
 279     copy_absolute(prefix, argv0_path);
 280     do {
 281         n = strlen(prefix);
 282         joinpath(prefix, lib_python);
 283         joinpath(prefix, LANDMARK);
 284         if (ismodule(prefix))
 285             return 1;
 286         prefix[n] = '\0';
 287         reduce(prefix);
 288     } while (prefix[0]);
 289
 290     /* Look at configure's PREFIX */
 291     strncpy(prefix, PREFIX, MAXPATHLEN);
 292     joinpath(prefix, lib_python);
 293     joinpath(prefix, LANDMARK);
 294     if (ismodule(prefix))
 295         return 1;
 296
 297     /* Fail */
 298     return 0;
 299 }
 300
 301
 302 /* search_for_exec_prefix requires that argv0_path be no more than
 303    MAXPATHLEN bytes long.
 304 */
 305 static int
 306 search_for_exec_prefix(char *argv0_path, char *home)
 307 {
 308     size_t n;
 309
 310     /* If PYTHONHOME is set, we believe it unconditionally */
 311     if (home) {
 312         char *delim;
 313         delim = strchr(home, DELIM);
 314         if (delim)
 315             strncpy(exec_prefix, delim+1, MAXPATHLEN);
 316         else
 317             strncpy(exec_prefix, home, MAXPATHLEN);
 318         joinpath(exec_prefix, lib_python);
 319         joinpath(exec_prefix, "lib-dynload");
 320         return 1;
 321     }
 322
 323     /* Check to see if argv[0] is in the build directory */
 324     strcpy(exec_prefix, argv0_path);
 325     joinpath(exec_prefix, "Modules/Setup");
 326     if (isfile(exec_prefix)) {
 327         reduce(exec_prefix);
 328         return -1;
 329     }
 330
 331     /* Search from argv0_path, until root is found */
 332     copy_absolute(exec_prefix, argv0_path);
 333     do {
 334         n = strlen(exec_prefix);
 335         joinpath(exec_prefix, lib_python);
 336         joinpath(exec_prefix, "lib-dynload");
 337         if (isdir(exec_prefix))
 338             return 1;
 339         exec_prefix[n] = '\0';
 340         reduce(exec_prefix);
 341     } while (exec_prefix[0]);
 342
 343     /* Look at configure's EXEC_PREFIX */
 344     strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);
 345     joinpath(exec_prefix, lib_python);
 346     joinpath(exec_prefix, "lib-dynload");
 347     if (isdir(exec_prefix))
 348         return 1;
 349
 350     /* Fail */
 351     return 0;
 352 }
 353
 354
 355 static void
 356 calculate_path(void)
 357 {
 358     extern char *Py_GetProgramName(void);
 359
 360     static char delimiter[2] = {DELIM, '\0'};
 361     static char separator[2] = {SEP, '\0'};
 362     char *pythonpath = PYTHONPATH;
 363     char *rtpypath = Py_GETENV("PYTHONPATH");
 364     char *home = Py_GetPythonHome();
 365     char *path = getenv("PATH");
 366     char *prog = Py_GetProgramName();
 367     char argv0_path[MAXPATHLEN+1];
 368     char zip_path[MAXPATHLEN+1];
 369     int pfound, efound; /* 1 if found; -1 if found build directory */
 370     char *buf;
 371     size_t bufsz;
 372     size_t prefixsz;
 373     char *defpath = pythonpath;
 374 #ifdef WITH_NEXT_FRAMEWORK
 375     NSModule pythonModule;
 376 #endif
 377
 378         /* If there is no slash in the argv0 path, then we have to
 379          * assume python is on the user's $PATH, since there's no
 380          * other way to find a directory to start the search from.  If
 381          * $PATH isn't exported, you lose.
 382          */
 383         if (strchr(prog, SEP))
 384                 strncpy(progpath, prog, MAXPATHLEN);
 385         else if (path) {
 386                 while (1) {
 387                         char *delim = strchr(path, DELIM);
 388
 389                         if (delim) {
 390                                 size_t len = delim - path;
 391                                 if (len > MAXPATHLEN)
 392                                         len = MAXPATHLEN;
 393                                 strncpy(progpath, path, len);
 394                                 *(progpath + len) = '\0';
 395                         }
 396                         else
 397                                 strncpy(progpath, path, MAXPATHLEN);
 398
 399                         joinpath(progpath, prog);
 400                         if (isxfile(progpath))
 401                                 break;
 402
 403                         if (!delim) {
 404                                 progpath[0] = '\0';
 405                                 break;
 406                         }
 407                         path = delim + 1;
 408                 }
 409         }
 410         else
 411                 progpath[0] = '\0';
 412         if (progpath[0] != SEP)
 413                 absolutize(progpath);
 414         strncpy(argv0_path, progpath, MAXPATHLEN);
 415         argv0_path[MAXPATHLEN] = '\0';
 416
 417 #ifdef WITH_NEXT_FRAMEWORK
 418         /* On Mac OS X we have a special case if we're running from a framework.
 419         ** This is because the python home should be set relative to the library,
 420         ** which is in the framework, not relative to the executable, which may
 421         ** be outside of the framework. Except when we're in the build directory...
 422         */
 423     pythonModule = NSModuleForSymbol(NSLookupAndBindSymbol("_Py_Initialize"));
 424     /* Use dylib functions to find out where the framework was loaded from */
 425     buf = (char *)NSLibraryNameForModule(pythonModule);
 426     if (buf != NULL) {
 427         /* We're in a framework. */
 428         /* See if we might be in the build directory. The framework in the
 429         ** build directory is incomplete, it only has the .dylib and a few
 430         ** needed symlinks, it doesn't have the Lib directories and such.
 431         ** If we're running with the framework from the build directory we must
 432         ** be running the interpreter in the build directory, so we use the
 433         ** build-directory-specific logic to find Lib and such.
 434         */
 435         strncpy(argv0_path, buf, MAXPATHLEN);
 436         reduce(argv0_path);
 437         joinpath(argv0_path, lib_python);
 438         joinpath(argv0_path, LANDMARK);
 439         if (!ismodule(argv0_path)) {
 440                 /* We are in the build directory so use the name of the
 441                    executable - we know that the absolute path is passed */
 442                 strncpy(argv0_path, prog, MAXPATHLEN);
 443         }
 444         else {
 445                 /* Use the location of the library as the progpath */
 446                 strncpy(argv0_path, buf, MAXPATHLEN);
 447         }
 448     }
 449 #endif
 450
 451 #if HAVE_READLINK
 452     {
 453         char tmpbuffer[MAXPATHLEN+1];
 454         int linklen = readlink(progpath, tmpbuffer, MAXPATHLEN);
 455         while (linklen != -1) {
 456             /* It's not null terminated! */
 457             tmpbuffer[linklen] = '\0';
 458             if (tmpbuffer[0] == SEP)
 459                 /* tmpbuffer should never be longer than MAXPATHLEN,
 460                    but extra check does not hurt */
 461                 strncpy(argv0_path, tmpbuffer, MAXPATHLEN);
 462             else {
 463                 /* Interpret relative to progpath */
 464                 reduce(argv0_path);
 465                 joinpath(argv0_path, tmpbuffer);
 466             }
 467             linklen = readlink(argv0_path, tmpbuffer, MAXPATHLEN);
 468         }
 469     }
 470 #endif /* HAVE_READLINK */
 471
 472     reduce(argv0_path);
 473     /* At this point, argv0_path is guaranteed to be less than
 474        MAXPATHLEN bytes long.
 475     */
 476
 477     if (!(pfound = search_for_prefix(argv0_path, home))) {
 478         if (!Py_FrozenFlag)
 479             fprintf(stderr,
 480                 "Could not find platform independent libraries <prefix>\n");
 481         strncpy(prefix, PREFIX, MAXPATHLEN);
 482         joinpath(prefix, lib_python);
 483     }
 484     else
 485         reduce(prefix);
 486
 487     strncpy(zip_path, prefix, MAXPATHLEN);
 488     zip_path[MAXPATHLEN] = '\0';
 489     if (pfound > 0) { /* Use the reduced prefix returned by Py_GetPrefix() */
 490         reduce(zip_path);
 491         reduce(zip_path);
 492     }
 493     else
 494         strncpy(zip_path, PREFIX, MAXPATHLEN);
 495     joinpath(zip_path, "lib/python00.zip");
 496     bufsz = strlen(zip_path);   /* Replace "00" with version */
 497     zip_path[bufsz - 6] = VERSION[0];
 498     zip_path[bufsz - 5] = VERSION[2];
 499
 500     if (!(efound = search_for_exec_prefix(argv0_path, home))) {
 501         if (!Py_FrozenFlag)
 502             fprintf(stderr,
 503                 "Could not find platform dependent libraries <exec_prefix>\n");
 504         strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);
 505         joinpath(exec_prefix, "lib/lib-dynload");
 506     }
 507     /* If we found EXEC_PREFIX do *not* reduce it!  (Yet.) */
 508
 509     if ((!pfound || !efound) && !Py_FrozenFlag)
 510         fprintf(stderr,
 511                 "Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]\n");
 512
 513     /* Calculate size of return buffer.
 514      */
 515     bufsz = 0;
 516
 517     if (rtpypath)
 518         bufsz += strlen(rtpypath) + 1;
 519
 520     prefixsz = strlen(prefix) + 1;
 521
 522     while (1) {
 523         char *delim = strchr(defpath, DELIM);
 524
 525         if (defpath[0] != SEP)
 526             /* Paths are relative to prefix */
 527             bufsz += prefixsz;
 528
 529         if (delim)
 530             bufsz += delim - defpath + 1;
 531         else {
 532             bufsz += strlen(defpath) + 1;
 533             break;
 534         }
 535         defpath = delim + 1;
 536     }
 537
 538     bufsz += strlen(zip_path) + 1;
 539     bufsz += strlen(exec_prefix) + 1;
 540
 541     /* This is the only malloc call in this file */
 542     buf = PyMem_Malloc(bufsz);
 543
 544     if (buf == NULL) {
 545         /* We can't exit, so print a warning and limp along */
 546         fprintf(stderr, "Not enough memory for dynamic PYTHONPATH.\n");
 547         fprintf(stderr, "Using default static PYTHONPATH.\n");
 548         module_search_path = PYTHONPATH;
 549     }
 550     else {
 551         /* Run-time value of $PYTHONPATH goes first */
 552         if (rtpypath) {
 553             strcpy(buf, rtpypath);
 554             strcat(buf, delimiter);
 555         }
 556         else
 557             buf[0] = '\0';
 558
 559         /* Next is the default zip path */
 560         strcat(buf, zip_path);
 561         strcat(buf, delimiter);
 562
 563         /* Next goes merge of compile-time $PYTHONPATH with
 564          * dynamically located prefix.
 565          */
 566         defpath = pythonpath;
 567         while (1) {
 568             char *delim = strchr(defpath, DELIM);
 569
 570             if (defpath[0] != SEP) {
 571                 strcat(buf, prefix);
 572                 strcat(buf, separator);
 573             }
 574
 575             if (delim) {
 576                 size_t len = delim - defpath + 1;
 577                 size_t end = strlen(buf) + len;
 578                 strncat(buf, defpath, len);
 579                 *(buf + end) = '\0';
 580             }
 581             else {
 582                 strcat(buf, defpath);
 583                 break;
 584             }
 585             defpath = delim + 1;
 586         }
 587         strcat(buf, delimiter);
 588
 589         /* Finally, on goes the directory for dynamic-load modules */
 590         strcat(buf, exec_prefix);
 591
 592         /* And publish the results */
 593         module_search_path = buf;
 594     }
 595
 596     /* Reduce prefix and exec_prefix to their essence,
 597      * e.g. /usr/local/lib/python1.5 is reduced to /usr/local.
 598      * If we're loading relative to the build directory,
 599      * return the compiled-in defaults instead.
 600      */
 601     if (pfound > 0) {
 602         reduce(prefix);
 603         reduce(prefix);
 604     }
 605     else
 606         strncpy(prefix, PREFIX, MAXPATHLEN);
 607
 608     if (efound > 0) {
 609         reduce(exec_prefix);
 610         reduce(exec_prefix);
 611         reduce(exec_prefix);
 612     }
 613     else
 614         strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);
 615 }
 616
 617
 618 /* External interface */
 619
 620 char *
 621 Py_GetPath(void)
 622 {
 623     if (!module_search_path)
 624         calculate_path();
 625     return module_search_path;
 626 }
 627
 628 char *
 629 Py_GetPrefix(void)
 630 {
 631     if (!module_search_path)
 632         calculate_path();
 633     return prefix;
 634 }
 635
 636 char *
 637 Py_GetExecPrefix(void)
 638 {
 639     if (!module_search_path)
 640         calculate_path();
 641     return exec_prefix;
 642 }
 643
 644 char *
 645 Py_GetProgramFullPath(void)
 646 {
 647     if (!module_search_path)
 648         calculate_path();
 649     return progpath;
 650 }