gcc/getpwd.c

   1 /* getpwd.c - get the working directory */
   2
   3 #include "config.h"
   4
   5 #include <errno.h>
   6 #include <sys/types.h>
   7 #include <sys/stat.h>
   8
   9 #ifndef errno
  10 extern int errno;
  11 #endif
  12
  13 /* Virtually every UN*X system now in common use (except for pre-4.3-tahoe
  14    BSD systems) now provides getcwd as called for by POSIX.  Allow for
  15    the few exceptions to the general rule here.  */
  16
  17 #if !(defined (POSIX) || defined (USG) || defined (VMS)) || defined (HAVE_GETWD)
  18 #include <sys/param.h>
  19 extern char *getwd ();
  20 #define getcwd(buf,len) getwd(buf)
  21 #ifdef MAXPATHLEN
  22 #define GUESSPATHLEN (MAXPATHLEN + 1)
  23 #else
  24 #define GUESSPATHLEN 100
  25 #endif
  26 #else /* (defined (USG) || defined (VMS)) */
  27 extern char *getcwd ();
  28 /* We actually use this as a starting point, not a limit.  */
  29 #define GUESSPATHLEN 100
  30 #endif /* (defined (USG) || defined (VMS)) */
  31 #ifdef WINNT
  32 #include <direct.h>
  33 #endif
  34
  35 char *getenv ();
  36 char *xmalloc ();
  37
  38 #ifndef VMS
  39
  40 /* Get the working directory.  Use the PWD environment variable if it's
  41    set correctly, since this is faster and gives more uniform answers
  42    to the user.  Yield the working directory if successful; otherwise,
  43    yield 0 and set errno.  */
  44
  45 char *
  46 getpwd ()
  47 {
  48   static char *pwd;
  49   static int failure_errno;
  50
  51   char *p = pwd;
  52   size_t s;
  53   struct stat dotstat, pwdstat;
  54
  55   if (!p && !(errno = failure_errno))
  56     {
  57       if (! ((p = getenv ("PWD")) != 0
  58              && *p == '/'
  59              && stat (p, &pwdstat) == 0
  60              && stat (".", &dotstat) == 0
  61              && dotstat.st_ino == pwdstat.st_ino
  62              && dotstat.st_dev == pwdstat.st_dev))
  63
  64         /* The shortcut didn't work.  Try the slow, ``sure'' way.  */
  65         for (s = GUESSPATHLEN;  ! getcwd (p = xmalloc (s), s);  s *= 2)
  66           {
  67             int e = errno;
  68             free (p);
  69 #ifdef ERANGE
  70             if (e != ERANGE)
  71 #endif
  72               {
  73                 errno = failure_errno = e;
  74                 p = 0;
  75                 break;
  76               }
  77           }
  78
  79       /* Cache the result.  This assumes that the program does
  80          not invoke chdir between calls to getpwd.  */
  81       pwd = p;
  82     }
  83   return p;
  84 }
  85
  86 #else   /* VMS */
  87
  88 #ifndef MAXPATHLEN
  89 #define MAXPATHLEN 255
  90 #endif
  91
  92 char *
  93 getpwd ()
  94 {
  95   static char *pwd = 0;
  96
  97   if (!pwd) pwd = getcwd (xmalloc (MAXPATHLEN+1), MAXPATHLEN+1);
  98   return pwd;
  99 }
 100
 101 #endif  /* VMS */