Modules/getpath.c

   1
   2 /* Return the initial module search path. */
   3
   4 #include "Python.h"
   5 #include "osdefs.h"
   6
   7 #include <sys/types.h>
   8 #include <sys/stat.h>
   9 #include <string.h>
  10
  11 #if HAVE_UNISTD_H
  12 #include <unistd.h>
  13 #endif /* HAVE_UNISTD_H */
  14
  15 #ifdef WITH_NEXT_FRAMEWORK
  16 #include <mach-o/dyld.h>
  17 #endif
  18
  19 /* Search in some common locations for the associated Python libraries.
  20  *
  21  * Two directories must be found, the platform independent directory
  22  * (prefix), containing the common .py and .pyc files, and the platform
  23  * dependent directory (exec_prefix), containing the shared library
  24  * modules.  Note that prefix and exec_prefix can be the same directory,
  25  * but for some installations, they are different.
  26  *
  27  * Py_GetPath() carries out separate searches for prefix and exec_prefix.
  28  * Each search tries a number of different locations until a ``landmark''
  29  * file or directory is found.  If no prefix or exec_prefix is found, a
  30  * warning message is issued and the preprocessor defined PREFIX and
  31  * EXEC_PREFIX are used (even though they will not work); python carries on
  32  * as best as is possible, but most imports will fail.
  33  *
  34  * Before any searches are done, the location of the executable is
  35  * determined.  If argv[0] has one or more slashs in it, it is used
  36  * unchanged.  Otherwise, it must have been invoked from the shell's path,
  37  * so we search $PATH for the named executable and use that.  If the
  38  * executable was not found on $PATH (or there was no $PATH environment
  39  * variable), the original argv[0] string is used.
  40  *
  41  * Next, the executable location is examined to see if it is a symbolic
  42  * link.  If so, the link is chased (correctly interpreting a relative
  43  * pathname if one is found) and the directory of the link target is used.
  44  *
  45  * Finally, argv0_path is set to the directory containing the executable
  46  * (i.e. the last component is stripped).
  47  *
  48  * With argv0_path in hand, we perform a number of steps.  The same steps
  49  * are performed for prefix and for exec_prefix, but with a different
  50  * landmark.
  51  *
  52  * Step 1. Are we running python out of the build directory?  This is
  53  * checked by looking for a different kind of landmark relative to
  54  * argv0_path.  For prefix, the landmark's path is derived from the VPATH
  55  * preprocessor variable (taking into account that its value is almost, but
  56  * not quite, what we need).  For exec_prefix, the landmark is
  57  * Modules/Setup.  If the landmark is found, we're done.
  58  *
  59  * For the remaining steps, the prefix landmark will always be
  60  * lib/python$VERSION/os.py and the exec_prefix will always be
  61  * lib/python$VERSION/lib-dynload, where $VERSION is Python's version
  62  * number as supplied by the Makefile.  Note that this means that no more
  63  * build directory checking is performed; if the first step did not find
  64  * the landmarks, the assumption is that python is running from an
  65  * installed setup.
  66  *
  67  * Step 2. See if the $PYTHONHOME environment variable points to the
  68  * installed location of the Python libraries.  If $PYTHONHOME is set, then
  69  * it points to prefix and exec_prefix.  $PYTHONHOME can be a single
  70  * directory, which is used for both, or the prefix and exec_prefix
  71  * directories separated by a colon.
  72  *
  73  * Step 3. Try to find prefix and exec_prefix relative to argv0_path,
  74  * backtracking up the path until it is exhausted.  This is the most common
  75  * step to succeed.  Note that if prefix and exec_prefix are different,
  76  * exec_prefix is more likely to be found; however if exec_prefix is a
  77  * subdirectory of prefix, both will be found.
  78  *
  79  * Step 4. Search the directories pointed to by the preprocessor variables
  80  * PREFIX and EXEC_PREFIX.  These are supplied by the Makefile but can be
  81  * passed in as options to the configure script.
  82  *
  83  * That's it!
  84  *
  85  * Well, almost.  Once we have determined prefix and exec_prefix, the
  86  * preprocessor variable PYTHONPATH is used to construct a path.  Each
  87  * relative path on PYTHONPATH is prefixed with prefix.  Then the directory
  88  * containing the shared library modules is appended.  The environment
  89  * variable $PYTHONPATH is inserted in front of it all.  Finally, the
  90  * prefix and exec_prefix globals are tweaked so they reflect the values
  91  * expected by other code, by stripping the "lib/python$VERSION/..." stuff
  92  * off.  If either points to the build directory, the globals are reset to
  93  * the corresponding preprocessor variables (so sys.prefix will reflect the
  94  * installation location, even though sys.path points into the build
  95  * directory).  This seems to make more sense given that currently the only
  96  * known use of sys.prefix and sys.exec_prefix is for the ILU installation
  97  * process to find the installed Python tree.
  98  */
  99
 100 #ifndef VERSION
 101 #define VERSION "2.0"
 102 #endif
 103
 104 #ifndef VPATH
 105 #define VPATH "."
 106 #endif
 107
 108 #ifndef PREFIX
 109 #define PREFIX "/usr/local"
 110 #endif
 111
 112 #ifndef EXEC_PREFIX
 113 #define EXEC_PREFIX PREFIX
 114 #endif
 115
 116 #ifndef PYTHONPATH
 117 /* I know this isn't K&R C, but the Makefile specifies it anyway */
 118 #define PYTHONPATH PREFIX "/lib/python" VERSION ":" \
 119               EXEC_PREFIX "/lib/python" VERSION "/lib-dynload"
 120 #endif
 121
 122 #ifndef LANDMARK
 123 #define LANDMARK "os.py"
 124 #endif
 125
 126 static char prefix[MAXPATHLEN+1];
 127 static char exec_prefix[MAXPATHLEN+1];
 128 static char progpath[MAXPATHLEN+1];
 129 static char *module_search_path = NULL;
 130 static char lib_python[] = "lib/python" VERSION;
 131
 132 static void
 133 reduce(char *dir)
 134 {
 135     size_t i = strlen(dir);
 136     while (i > 0 && dir[i] != SEP)
 137         --i;
 138     dir[i] = '\0';
 139 }
 140
 141
 142 #ifndef S_ISREG
 143 #define S_ISREG(x) (((x) & S_IFMT) == S_IFREG)
 144 #endif
 145
 146 #ifndef S_ISDIR
 147 #define S_ISDIR(x) (((x) & S_IFMT) == S_IFDIR)
 148 #endif
 149
 150 static int
 151 isfile(char *filename)          /* Is file, not directory */
 152 {
 153     struct stat buf;
 154     if (stat(filename, &buf) != 0)
 155         return 0;
 156     if (!S_ISREG(buf.st_mode))
 157         return 0;
 158     return 1;
 159 }
 160
 161
 162 static int
 163 ismodule(char *filename)        /* Is module -- check for .pyc/.pyo too */
 164 {
 165     if (isfile(filename))
 166         return 1;
 167
 168     /* Check for the compiled version of prefix. */
 169     if (strlen(filename) < MAXPATHLEN) {
 170         strcat(filename, Py_OptimizeFlag ? "o" : "c");
 171         if (isfile(filename))
 172             return 1;
 173     }
 174     return 0;
 175 }
 176
 177
 178 static int
 179 isxfile(char *filename)         /* Is executable file */
 180 {
 181     struct stat buf;
 182     if (stat(filename, &buf) != 0)
 183         return 0;
 184     if (!S_ISREG(buf.st_mode))
 185         return 0;
 186     if ((buf.st_mode & 0111) == 0)
 187         return 0;
 188     return 1;
 189 }
 190
 191
 192 static int
 193 isdir(char *filename)                   /* Is directory */
 194 {
 195     struct stat buf;
 196     if (stat(filename, &buf) != 0)
 197         return 0;
 198     if (!S_ISDIR(buf.st_mode))
 199         return 0;
 200     return 1;
 201 }
 202
 203
 204 /* joinpath requires that any buffer argument passed to it has at
 205    least MAXPATHLEN + 1 bytes allocated.  If this requirement is met,
 206    it guarantees that it will never overflow the buffer.  If stuff
 207    is too long, buffer will contain a truncated copy of stuff.
 208 */
 209 static void
 210 joinpath(char *buffer, char *stuff)
 211 {
 212     size_t n, k;
 213     if (stuff[0] == SEP)
 214         n = 0;
 215     else {
 216         n = strlen(buffer);
 217         if (n > 0 && buffer[n-1] != SEP && n < MAXPATHLEN)
 218             buffer[n++] = SEP;
 219     }
 220     k = strlen(stuff);
 221     if (n + k > MAXPATHLEN)
 222         k = MAXPATHLEN - n;
 223     strncpy(buffer+n, stuff, k);
 224     buffer[n+k] = '\0';
 225 }
 226
 227 /* init_path_from_argv0 requirs that path be allocated at least
 228    MAXPATHLEN + 1 bytes and that argv0_path be no more than MAXPATHLEN
 229    bytes.
 230 */
 231 static void
 232 init_path_from_argv0(char *path, char *argv0_path)
 233 {
 234     if (argv0_path[0] == '/')
 235         strcpy(path, argv0_path);
 236     else if (argv0_path[0] == '.') {
 237         getcwd(path, MAXPATHLEN);
 238         if (argv0_path[1] == '/')
 239             joinpath(path, argv0_path + 2);
 240         else
 241             joinpath(path, argv0_path);
 242     }
 243     else {
 244         getcwd(path, MAXPATHLEN);
 245         joinpath(path, argv0_path);
 246     }
 247 }
 248
 249 /* search_for_prefix requires that argv0_path be no more than MAXPATHLEN
 250    bytes long.
 251 */
 252 static int
 253 search_for_prefix(char *argv0_path, char *home)
 254 {
 255     size_t n;
 256     char *vpath;
 257
 258     /* If PYTHONHOME is set, we believe it unconditionally */
 259     if (home) {
 260         char *delim;
 261         strncpy(prefix, home, MAXPATHLEN);
 262         delim = strchr(prefix, DELIM);
 263         if (delim)
 264             *delim = '\0';
 265         joinpath(prefix, lib_python);
 266         joinpath(prefix, LANDMARK);
 267         return 1;
 268     }
 269
 270     /* Check to see if argv[0] is in the build directory */
 271     strcpy(prefix, argv0_path);
 272     joinpath(prefix, "Modules/Setup");
 273     if (isfile(prefix)) {
 274         /* Check VPATH to see if argv0_path is in the build directory.
 275          * Complication: the VPATH passed in is relative to the
 276          * Modules build directory and points to the Modules source
 277          * directory; we need it relative to the build tree and
 278          * pointing to the source tree.  Solution: chop off a leading
 279          * ".." (but only if it's there -- it could be an absolute
 280          * path) and chop off the final component (assuming it's
 281          * "Modules").
 282          */
 283         vpath = VPATH;
 284         if (vpath[0] == '.' && vpath[1] == '.' && vpath[2] == '/')
 285             vpath += 3;
 286         strcpy(prefix, argv0_path);
 287         joinpath(prefix, vpath);
 288         reduce(prefix);
 289         joinpath(prefix, "Lib");
 290         joinpath(prefix, LANDMARK);
 291         if (ismodule(prefix))
 292             return -1;
 293     }
 294
 295     /* Search from argv0_path, until root is found */
 296     init_path_from_argv0(prefix, argv0_path);
 297     do {
 298         n = strlen(prefix);
 299         joinpath(prefix, lib_python);
 300         joinpath(prefix, LANDMARK);
 301         if (ismodule(prefix))
 302             return 1;
 303         prefix[n] = '\0';
 304         reduce(prefix);
 305     } while (prefix[0]);
 306
 307     /* Look at configure's PREFIX */
 308     strncpy(prefix, PREFIX, MAXPATHLEN);
 309     joinpath(prefix, lib_python);
 310     joinpath(prefix, LANDMARK);
 311     if (ismodule(prefix))
 312         return 1;
 313
 314     /* Fail */
 315     return 0;
 316 }
 317
 318
 319 /* search_for_exec_prefix requires that argv0_path be no more than
 320    MAXPATHLEN bytes long.
 321 */
 322 static int
 323 search_for_exec_prefix(char *argv0_path, char *home)
 324 {
 325     size_t n;
 326
 327     /* If PYTHONHOME is set, we believe it unconditionally */
 328     if (home) {
 329         char *delim;
 330         delim = strchr(home, DELIM);
 331         if (delim)
 332             strncpy(exec_prefix, delim+1, MAXPATHLEN);
 333         else
 334             strncpy(exec_prefix, home, MAXPATHLEN);
 335         joinpath(exec_prefix, lib_python);
 336         joinpath(exec_prefix, "lib-dynload");
 337         return 1;
 338     }
 339
 340     /* Check to see if argv[0] is in the build directory */
 341     strcpy(exec_prefix, argv0_path);
 342     joinpath(exec_prefix, "Modules/Setup");
 343     if (isfile(exec_prefix)) {
 344         reduce(exec_prefix);
 345         return -1;
 346     }
 347
 348     /* Search from argv0_path, until root is found */
 349     init_path_from_argv0(exec_prefix, argv0_path);
 350     do {
 351         n = strlen(exec_prefix);
 352         joinpath(exec_prefix, lib_python);
 353         joinpath(exec_prefix, "lib-dynload");
 354         if (isdir(exec_prefix))
 355             return 1;
 356         exec_prefix[n] = '\0';
 357         reduce(exec_prefix);
 358     } while (exec_prefix[0]);
 359
 360     /* Look at configure's EXEC_PREFIX */
 361     strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);
 362     joinpath(exec_prefix, lib_python);
 363     joinpath(exec_prefix, "lib-dynload");
 364     if (isdir(exec_prefix))
 365         return 1;
 366
 367     /* Fail */
 368     return 0;
 369 }
 370
 371
 372 static void
 373 calculate_path(void)
 374 {
 375     extern char *Py_GetProgramName(void);
 376
 377     static char delimiter[2] = {DELIM, '\0'};
 378     static char separator[2] = {SEP, '\0'};
 379     char *pythonpath = PYTHONPATH;
 380     char *rtpypath = getenv("PYTHONPATH");
 381     char *home = Py_GetPythonHome();
 382     char *path = getenv("PATH");
 383     char *prog = Py_GetProgramName();
 384     char argv0_path[MAXPATHLEN+1];
 385     int pfound, efound; /* 1 if found; -1 if found build directory */
 386     char *buf;
 387     size_t bufsz;
 388     size_t prefixsz;
 389     char *defpath = pythonpath;
 390 #ifdef WITH_NEXT_FRAMEWORK
 391     NSModule pythonModule;
 392 #endif
 393
 394 #ifdef WITH_NEXT_FRAMEWORK
 395     /* XXX Need to check this code for buffer overflows */
 396     pythonModule = NSModuleForSymbol(NSLookupAndBindSymbol("_Py_Initialize"));
 397     /* Use dylib functions to find out where the framework was loaded from */
 398     buf = NSLibraryNameForModule(pythonModule);
 399     if (buf != NULL) {
 400         /* We're in a framework. */
 401         strcpy(progpath, buf);
 402
 403         /* Frameworks have support for versioning */
 404         strcpy(lib_python, "lib");
 405     }
 406     else {
 407         /* If we're not in a framework, fall back to the old way
 408            (even though NSNameOfModule() probably does the same thing.) */
 409 #endif
 410
 411         /* If there is no slash in the argv0 path, then we have to
 412          * assume python is on the user's $PATH, since there's no
 413          * other way to find a directory to start the search from.  If
 414          * $PATH isn't exported, you lose.
 415          */
 416         if (strchr(prog, SEP))
 417             strncpy(progpath, prog, MAXPATHLEN);
 418         else if (path) {
 419             int bufspace = MAXPATHLEN;
 420             while (1) {
 421                 char *delim = strchr(path, DELIM);
 422
 423                 if (delim) {
 424                     size_t len = delim - path;
 425                     if (len > bufspace)
 426                         len = bufspace;
 427                     strncpy(progpath, path, len);
 428                     *(progpath + len) = '\0';
 429                     bufspace -= len;
 430                 }
 431                 else
 432                     strncpy(progpath, path, bufspace);
 433
 434                 joinpath(progpath, prog);
 435                 if (isxfile(progpath))
 436                     break;
 437
 438                 if (!delim) {
 439                     progpath[0] = '\0';
 440                     break;
 441                 }
 442                 path = delim + 1;
 443             }
 444         }
 445         else
 446             progpath[0] = '\0';
 447 #ifdef WITH_NEXT_FRAMEWORK
 448     }
 449 #endif
 450
 451     strncpy(argv0_path, progpath, MAXPATHLEN);
 452
 453 #if HAVE_READLINK
 454     {
 455         char tmpbuffer[MAXPATHLEN+1];
 456         int linklen = readlink(progpath, tmpbuffer, MAXPATHLEN);
 457         while (linklen != -1) {
 458             /* It's not null terminated! */
 459             tmpbuffer[linklen] = '\0';
 460             if (tmpbuffer[0] == SEP)
 461                 /* tmpbuffer should never be longer than MAXPATHLEN,
 462                    but extra check does not hurt */
 463                 strncpy(argv0_path, tmpbuffer, MAXPATHLEN);
 464             else {
 465                 /* Interpret relative to progpath */
 466                 reduce(argv0_path);
 467                 joinpath(argv0_path, tmpbuffer);
 468             }
 469             linklen = readlink(argv0_path, tmpbuffer, MAXPATHLEN);
 470         }
 471     }
 472 #endif /* HAVE_READLINK */
 473
 474     reduce(argv0_path);
 475     /* At this point, argv0_path is guaranteed to be less than
 476        MAXPATHLEN bytes long.
 477     */
 478
 479     if (!(pfound = search_for_prefix(argv0_path, home))) {
 480         if (!Py_FrozenFlag)
 481             fprintf(stderr,
 482                     "Could not find platform independent libraries <prefix>\n");
 483         strncpy(prefix, PREFIX, MAXPATHLEN);
 484         joinpath(prefix, lib_python);
 485     }
 486     else
 487         reduce(prefix);
 488
 489     if (!(efound = search_for_exec_prefix(argv0_path, home))) {
 490         if (!Py_FrozenFlag)
 491             fprintf(stderr,
 492                     "Could not find platform dependent libraries <exec_prefix>\n");
 493         strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);
 494         joinpath(exec_prefix, "lib/lib-dynload");
 495     }
 496     /* If we found EXEC_PREFIX do *not* reduce it!  (Yet.) */
 497
 498     if ((!pfound || !efound) && !Py_FrozenFlag)
 499         fprintf(stderr,
 500                 "Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]\n");
 501
 502     /* Calculate size of return buffer.
 503      */
 504     bufsz = 0;
 505
 506     if (rtpypath)
 507         bufsz += strlen(rtpypath) + 1;
 508
 509     prefixsz = strlen(prefix) + 1;
 510
 511     while (1) {
 512         char *delim = strchr(defpath, DELIM);
 513
 514         if (defpath[0] != SEP)
 515             /* Paths are relative to prefix */
 516             bufsz += prefixsz;
 517
 518         if (delim)
 519             bufsz += delim - defpath + 1;
 520         else {
 521             bufsz += strlen(defpath) + 1;
 522             break;
 523         }
 524         defpath = delim + 1;
 525     }
 526
 527     bufsz += strlen(exec_prefix) + 1;
 528
 529     /* This is the only malloc call in this file */
 530     buf = PyMem_Malloc(bufsz);
 531
 532     if (buf == NULL) {
 533         /* We can't exit, so print a warning and limp along */
 534         fprintf(stderr, "Not enough memory for dynamic PYTHONPATH.\n");
 535         fprintf(stderr, "Using default static PYTHONPATH.\n");
 536         module_search_path = PYTHONPATH;
 537     }
 538     else {
 539         /* Run-time value of $PYTHONPATH goes first */
 540         if (rtpypath) {
 541             strcpy(buf, rtpypath);
 542             strcat(buf, delimiter);
 543         }
 544         else
 545             buf[0] = '\0';
 546
 547         /* Next goes merge of compile-time $PYTHONPATH with
 548          * dynamically located prefix.
 549          */
 550         defpath = pythonpath;
 551         while (1) {
 552             char *delim = strchr(defpath, DELIM);
 553
 554             if (defpath[0] != SEP) {
 555                 strcat(buf, prefix);
 556                 strcat(buf, separator);
 557             }
 558
 559             if (delim) {
 560                 size_t len = delim - defpath + 1;
 561                 size_t end = strlen(buf) + len;
 562                 strncat(buf, defpath, len);
 563                 *(buf + end) = '\0';
 564             }
 565             else {
 566                 strcat(buf, defpath);
 567                 break;
 568             }
 569             defpath = delim + 1;
 570         }
 571         strcat(buf, delimiter);
 572
 573         /* Finally, on goes the directory for dynamic-load modules */
 574         strcat(buf, exec_prefix);
 575
 576         /* And publish the results */
 577         module_search_path = buf;
 578     }
 579
 580     /* Reduce prefix and exec_prefix to their essence,
 581      * e.g. /usr/local/lib/python1.5 is reduced to /usr/local.
 582      * If we're loading relative to the build directory,
 583      * return the compiled-in defaults instead.
 584      */
 585     if (pfound > 0) {
 586         reduce(prefix);
 587         reduce(prefix);
 588     }
 589     else
 590         strncpy(prefix, PREFIX, MAXPATHLEN);
 591
 592     if (efound > 0) {
 593         reduce(exec_prefix);
 594         reduce(exec_prefix);
 595         reduce(exec_prefix);
 596     }
 597     else
 598         strncpy(exec_prefix, EXEC_PREFIX, MAXPATHLEN);
 599 }
 600
 601
 602 /* External interface */
 603
 604 char *
 605 Py_GetPath(void)
 606 {
 607     if (!module_search_path)
 608         calculate_path();
 609     return module_search_path;
 610 }
 611
 612 char *
 613 Py_GetPrefix(void)
 614 {
 615     if (!module_search_path)
 616         calculate_path();
 617     return prefix;
 618 }
 619
 620 char *
 621 Py_GetExecPrefix(void)
 622 {
 623     if (!module_search_path)
 624         calculate_path();
 625     return exec_prefix;
 626 }
 627
 628 char *
 629 Py_GetProgramFullPath(void)
 630 {
 631     if (!module_search_path)
 632         calculate_path();
 633     return progpath;
 634 }