libiberty/make-relative-prefix.c

   1 /* Relative (relocatable) prefix support.
   2    Copyright (C) 1987-2017 Free Software Foundation, Inc.
   3
   4 This file is part of libiberty.
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 2, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to the Free
  18 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
  19 02110-1301, USA.  */
  20
  21 /*
  22
  23 @deftypefn Extension {const char*} make_relative_prefix (const char *@var{progname}, @
  24   const char *@var{bin_prefix}, const char *@var{prefix})
  25
  26 Given three paths @var{progname}, @var{bin_prefix}, @var{prefix},
  27 return the path that is in the same position relative to
  28 @var{progname}'s directory as @var{prefix} is relative to
  29 @var{bin_prefix}.  That is, a string starting with the directory
  30 portion of @var{progname}, followed by a relative pathname of the
  31 difference between @var{bin_prefix} and @var{prefix}.
  32
  33 If @var{progname} does not contain any directory separators,
  34 @code{make_relative_prefix} will search @env{PATH} to find a program
  35 named @var{progname}.  Also, if @var{progname} is a symbolic link,
  36 the symbolic link will be resolved.
  37
  38 For example, if @var{bin_prefix} is @code{/alpha/beta/gamma/gcc/delta},
  39 @var{prefix} is @code{/alpha/beta/gamma/omega/}, and @var{progname} is
  40 @code{/red/green/blue/gcc}, then this function will return
  41 @code{/red/green/blue/../../omega/}.
  42
  43 The return value is normally allocated via @code{malloc}.  If no
  44 relative prefix can be found, return @code{NULL}.
  45
  46 @end deftypefn
  47
  48 */
  49
  50 #ifdef HAVE_CONFIG_H
  51 #include "config.h"
  52 #endif
  53
  54 #ifdef HAVE_STDLIB_H
  55 #include <stdlib.h>
  56 #endif
  57 #ifdef HAVE_UNISTD_H
  58 #include <unistd.h>
  59 #endif
  60 #ifdef HAVE_SYS_STAT_H
  61 #include <sys/stat.h>
  62 #endif
  63
  64 #include <string.h>
  65
  66 #include "ansidecl.h"
  67 #include "libiberty.h"
  68
  69 #ifndef R_OK
  70 #define R_OK 4
  71 #define W_OK 2
  72 #define X_OK 1
  73 #endif
  74
  75 #ifndef DIR_SEPARATOR
  76 #  define DIR_SEPARATOR '/'
  77 #endif
  78
  79 #if defined (_WIN32) || defined (__MSDOS__) \
  80     || defined (__DJGPP__) || defined (__OS2__)
  81 #  define HAVE_DOS_BASED_FILE_SYSTEM
  82 #  define HAVE_HOST_EXECUTABLE_SUFFIX
  83 #  define HOST_EXECUTABLE_SUFFIX ".exe"
  84 #  ifndef DIR_SEPARATOR_2
  85 #    define DIR_SEPARATOR_2 '\\'
  86 #  endif
  87 #  define PATH_SEPARATOR ';'
  88 #else
  89 #  define PATH_SEPARATOR ':'
  90 #endif
  91
  92 #ifndef DIR_SEPARATOR_2
  93 #  define IS_DIR_SEPARATOR(ch) ((ch) == DIR_SEPARATOR)
  94 #else
  95 #  define IS_DIR_SEPARATOR(ch) \
  96         (((ch) == DIR_SEPARATOR) || ((ch) == DIR_SEPARATOR_2))
  97 #endif
  98
  99 #define DIR_UP ".."
 100
 101 static char *save_string (const char *, int);
 102 static char **split_directories (const char *, int *);
 103 static void free_split_directories (char **);
 104
 105 static char *
 106 save_string (const char *s, int len)
 107 {
 108   char *result = (char *) malloc (len + 1);
 109
 110   memcpy (result, s, len);
 111   result[len] = 0;
 112   return result;
 113 }
 114
 115 /* Split a filename into component directories.  */
 116
 117 static char **
 118 split_directories (const char *name, int *ptr_num_dirs)
 119 {
 120   int num_dirs = 0;
 121   char **dirs;
 122   const char *p, *q;
 123   int ch;
 124
 125   /* Count the number of directories.  Special case MSDOS disk names as part
 126      of the initial directory.  */
 127   p = name;
 128 #ifdef HAVE_DOS_BASED_FILE_SYSTEM
 129   if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
 130     {
 131       p += 3;
 132       num_dirs++;
 133     }
 134 #endif /* HAVE_DOS_BASED_FILE_SYSTEM */
 135
 136   while ((ch = *p++) != '\0')
 137     {
 138       if (IS_DIR_SEPARATOR (ch))
 139         {
 140           num_dirs++;
 141           while (IS_DIR_SEPARATOR (*p))
 142             p++;
 143         }
 144     }
 145
 146   dirs = (char **) malloc (sizeof (char *) * (num_dirs + 2));
 147   if (dirs == NULL)
 148     return NULL;
 149
 150   /* Now copy the directory parts.  */
 151   num_dirs = 0;
 152   p = name;
 153 #ifdef HAVE_DOS_BASED_FILE_SYSTEM
 154   if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
 155     {
 156       dirs[num_dirs++] = save_string (p, 3);
 157       if (dirs[num_dirs - 1] == NULL)
 158         {
 159           free (dirs);
 160           return NULL;
 161         }
 162       p += 3;
 163     }
 164 #endif /* HAVE_DOS_BASED_FILE_SYSTEM */
 165
 166   q = p;
 167   while ((ch = *p++) != '\0')
 168     {
 169       if (IS_DIR_SEPARATOR (ch))
 170         {
 171           while (IS_DIR_SEPARATOR (*p))
 172             p++;
 173
 174           dirs[num_dirs++] = save_string (q, p - q);
 175           if (dirs[num_dirs - 1] == NULL)
 176             {
 177               dirs[num_dirs] = NULL;
 178               free_split_directories (dirs);
 179               return NULL;
 180             }
 181           q = p;
 182         }
 183     }
 184
 185   if (p - 1 - q > 0)
 186     dirs[num_dirs++] = save_string (q, p - 1 - q);
 187   dirs[num_dirs] = NULL;
 188
 189   if (dirs[num_dirs - 1] == NULL)
 190     {
 191       free_split_directories (dirs);
 192       return NULL;
 193     }
 194
 195   if (ptr_num_dirs)
 196     *ptr_num_dirs = num_dirs;
 197   return dirs;
 198 }
 199
 200 /* Release storage held by split directories.  */
 201
 202 static void
 203 free_split_directories (char **dirs)
 204 {
 205   int i = 0;
 206
 207   if (dirs != NULL)
 208     {
 209       while (dirs[i] != NULL)
 210         free (dirs[i++]);
 211
 212       free ((char *) dirs);
 213     }
 214 }
 215
 216 /* Given three strings PROGNAME, BIN_PREFIX, PREFIX, return a string that gets
 217    to PREFIX starting with the directory portion of PROGNAME and a relative
 218    pathname of the difference between BIN_PREFIX and PREFIX.
 219
 220    For example, if BIN_PREFIX is /alpha/beta/gamma/gcc/delta, PREFIX is
 221    /alpha/beta/gamma/omega/, and PROGNAME is /red/green/blue/gcc, then this
 222    function will return /red/green/blue/../../omega/.
 223
 224    If no relative prefix can be found, return NULL.  */
 225
 226 static char *
 227 make_relative_prefix_1 (const char *progname, const char *bin_prefix,
 228                         const char *prefix, const int resolve_links)
 229 {
 230   char **prog_dirs = NULL, **bin_dirs = NULL, **prefix_dirs = NULL;
 231   int prog_num, bin_num, prefix_num;
 232   int i, n, common;
 233   int needed_len;
 234   char *ret = NULL, *ptr, *full_progname;
 235   char *alloc_ptr = NULL;
 236
 237   if (progname == NULL || bin_prefix == NULL || prefix == NULL)
 238     return NULL;
 239
 240   /* If there is no full pathname, try to find the program by checking in each
 241      of the directories specified in the PATH environment variable.  */
 242   if (lbasename (progname) == progname)
 243     {
 244       char *temp;
 245
 246       temp = getenv ("PATH");
 247       if (temp)
 248         {
 249           char *startp, *endp, *nstore;
 250           size_t prefixlen = strlen (temp) + 1;
 251           size_t len;
 252           if (prefixlen < 2)
 253             prefixlen = 2;
 254
 255           len = prefixlen + strlen (progname) + 1;
 256 #ifdef HAVE_HOST_EXECUTABLE_SUFFIX
 257           len += strlen (HOST_EXECUTABLE_SUFFIX);
 258 #endif
 259           if (len < MAX_ALLOCA_SIZE)
 260             nstore = (char *) alloca (len);
 261           else
 262             alloc_ptr = nstore = (char *) malloc (len);
 263
 264           startp = endp = temp;
 265           while (1)
 266             {
 267               if (*endp == PATH_SEPARATOR || *endp == 0)
 268                 {
 269                   if (endp == startp)
 270                     {
 271                       nstore[0] = '.';
 272                       nstore[1] = DIR_SEPARATOR;
 273                       nstore[2] = '\0';
 274                     }
 275                   else
 276                     {
 277                       memcpy (nstore, startp, endp - startp);
 278                       if (! IS_DIR_SEPARATOR (endp[-1]))
 279                         {
 280                           nstore[endp - startp] = DIR_SEPARATOR;
 281                           nstore[endp - startp + 1] = 0;
 282                         }
 283                       else
 284                         nstore[endp - startp] = 0;
 285                     }
 286                   strcat (nstore, progname);
 287                   if (! access (nstore, X_OK)
 288 #ifdef HAVE_HOST_EXECUTABLE_SUFFIX
 289                       || ! access (strcat (nstore, HOST_EXECUTABLE_SUFFIX), X_OK)
 290 #endif
 291                       )
 292                     {
 293 #if defined (HAVE_SYS_STAT_H) && defined (S_ISREG)
 294                       struct stat st;
 295                       if (stat (nstore, &st) >= 0 && S_ISREG (st.st_mode))
 296 #endif
 297                         {
 298                           progname = nstore;
 299                           break;
 300                         }
 301                     }
 302
 303                   if (*endp == 0)
 304                     break;
 305                   endp = startp = endp + 1;
 306                 }
 307               else
 308                 endp++;
 309             }
 310         }
 311     }
 312
 313   if (resolve_links)
 314     full_progname = lrealpath (progname);
 315   else
 316     full_progname = strdup (progname);
 317   if (full_progname == NULL)
 318     goto bailout;
 319
 320   prog_dirs = split_directories (full_progname, &prog_num);
 321   free (full_progname);
 322   if (prog_dirs == NULL)
 323     goto bailout;
 324
 325   bin_dirs = split_directories (bin_prefix, &bin_num);
 326   if (bin_dirs == NULL)
 327     goto bailout;
 328
 329   /* Remove the program name from comparison of directory names.  */
 330   prog_num--;
 331
 332   /* If we are still installed in the standard location, we don't need to
 333      specify relative directories.  Also, if argv[0] still doesn't contain
 334      any directory specifiers after the search above, then there is not much
 335      we can do.  */
 336   if (prog_num == bin_num)
 337     {
 338       for (i = 0; i < bin_num; i++)
 339         {
 340           if (strcmp (prog_dirs[i], bin_dirs[i]) != 0)
 341             break;
 342         }
 343
 344       if (prog_num <= 0 || i == bin_num)
 345         goto bailout;
 346     }
 347
 348   prefix_dirs = split_directories (prefix, &prefix_num);
 349   if (prefix_dirs == NULL)
 350     goto bailout;
 351
 352   /* Find how many directories are in common between bin_prefix & prefix.  */
 353   n = (prefix_num < bin_num) ? prefix_num : bin_num;
 354   for (common = 0; common < n; common++)
 355     {
 356       if (strcmp (bin_dirs[common], prefix_dirs[common]) != 0)
 357         break;
 358     }
 359
 360   /* If there are no common directories, there can be no relative prefix.  */
 361   if (common == 0)
 362     goto bailout;
 363
 364   /* Two passes: first figure out the size of the result string, and
 365      then construct it.  */
 366   needed_len = 0;
 367   for (i = 0; i < prog_num; i++)
 368     needed_len += strlen (prog_dirs[i]);
 369   needed_len += sizeof (DIR_UP) * (bin_num - common);
 370   for (i = common; i < prefix_num; i++)
 371     needed_len += strlen (prefix_dirs[i]);
 372   needed_len += 1; /* Trailing NUL.  */
 373
 374   ret = (char *) malloc (needed_len);
 375   if (ret == NULL)
 376     goto bailout;
 377
 378   /* Build up the pathnames in argv[0].  */
 379   *ret = '\0';
 380   for (i = 0; i < prog_num; i++)
 381     strcat (ret, prog_dirs[i]);
 382
 383   /* Now build up the ..'s.  */
 384   ptr = ret + strlen(ret);
 385   for (i = common; i < bin_num; i++)
 386     {
 387       strcpy (ptr, DIR_UP);
 388       ptr += sizeof (DIR_UP) - 1;
 389       *(ptr++) = DIR_SEPARATOR;
 390     }
 391   *ptr = '\0';
 392
 393   /* Put in directories to move over to prefix.  */
 394   for (i = common; i < prefix_num; i++)
 395     strcat (ret, prefix_dirs[i]);
 396
 397  bailout:
 398   free_split_directories (prog_dirs);
 399   free_split_directories (bin_dirs);
 400   free_split_directories (prefix_dirs);
 401   free (alloc_ptr);
 402
 403   return ret;
 404 }
 405
 406
 407 /* Do the full job, including symlink resolution.
 408    This path will find files installed in the same place as the
 409    program even when a soft link has been made to the program
 410    from somwhere else. */
 411
 412 char *
 413 make_relative_prefix (const char *progname, const char *bin_prefix,
 414                       const char *prefix)
 415 {
 416   return make_relative_prefix_1 (progname, bin_prefix, prefix, 1);
 417 }
 418
 419 /* Make the relative pathname without attempting to resolve any links.
 420    '..' etc may also be left in the pathname.
 421    This will find the files the user meant the program to find if the
 422    installation is patched together with soft links. */
 423
 424 char *
 425 make_relative_prefix_ignore_links (const char *progname,
 426                                    const char *bin_prefix,
 427                                    const char *prefix)
 428 {
 429   return make_relative_prefix_1 (progname, bin_prefix, prefix, 0);
 430 }
 431