Fix the !HAVE_GETCWD_NULL code to behave more

[gnulib.git] / lib / xgetcwd.c

diff --git a/lib/xgetcwd.c b/lib/xgetcwd.c
index 896be5d..85ac368 100644 (file)
--- a/lib/xgetcwd.c
+++ b/lib/xgetcwd.c
@@ -1,5 +1,5 @@
 /* xgetcwd.c -- return current directory with unlimited length
-   Copyright (C) 1992, 1996, 2000 Free Software Foundation, Inc.
+   Copyright (C) 1992, 1996, 2000, 2001 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -28,58 +28,61 @@ extern int errno;
 #endif
 
 #include <sys/types.h>
-#include "pathmax.h"
+
+#if HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
 
 #if HAVE_GETCWD
 char *getcwd ();
 #else
+# include "pathmax.h"
+# define INITIAL_BUFFER_SIZE (PATH_MAX + 1)
 char *getwd ();
 # define getcwd(Buf, Max) getwd (Buf)
 #endif
 
-extern void *xmalloc ();
-extern char *xstrdup ();
-extern void free ();
-
 /* Return the current directory, newly allocated, arbitrarily long.
    Return NULL and set errno on error. */
 
 char *
 xgetcwd ()
 {
-  char *ret;
-  unsigned path_max;
-  char buf[1024];
+#if HAVE_GETCWD_NULL
+  return getcwd (NULL, 0);
+#else
 
-  errno = 0;
-  ret = getcwd (buf, sizeof (buf));
-  if (ret != NULL)
-    return xstrdup (buf);
-  if (errno != ERANGE)
-    return NULL;
+  /* The initial buffer size for the working directory.  A power of 2
+     detects arithmetic overflow earlier, but is not required.  */
+# ifndef INITIAL_BUFFER_SIZE
+#  define INITIAL_BUFFER_SIZE 128
+# endif
 
-  path_max = (unsigned) PATH_MAX;
-  path_max += 2;               /* The getcwd docs say to do this. */
+  size_t buf_size = INITIAL_BUFFER_SIZE;
 
-  for (;;)
+  while (1)
     {
-      char *cwd = (char *) xmalloc (path_max);
-
-      errno = 0;
-      ret = getcwd (cwd, path_max);
-      if (ret != NULL)
-       return ret;
-      if (errno != ERANGE)
+      char *cwd;
+      int saved_errno;
+      char *buf = malloc (buf_size);
+      if (! buf)
+       return NULL;
+      cwd = getcwd (buf, buf_size);
+      if (cwd)
+       return cwd;
+      saved_errno = errno;
+      free (buf);
+      if (saved_errno != ERANGE)
+       return NULL;
+      buf_size *= 2;
+      if (buf_size == 0)
        {
-         int save_errno = errno;
-         free (cwd);
-         errno = save_errno;
+         errno = ENOMEM;
          return NULL;
        }
-
-      free (cwd);
-
-      path_max += path_max / 16;
-      path_max += 32;
     }
+#endif
 }