include/

	* libiberty.h (make_relative_prefix): Add prototype.
libiberty/
	* Makefile.in: Add make-relative-prefix.c.
	* make-relative-prefix.c: New file.
	* functions.texi: Rebuilt.
gcc/
	* gcc.c (make_relative_prefix, split_directories)
	(free_split_directories): Removed.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@59385 138bc75d-0d04-0410-961f-82ee72b054a4

8 files changed, 432 insertions, 249 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index cf02ad6a463..4500b2c24ed 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,10 @@
 2002-11-22  Daniel Jacobowitz  <drow@mvista.com>
 
+	* gcc.c (make_relative_prefix, split_directories)
+	(free_split_directories): Removed.
+
+2002-11-22  Daniel Jacobowitz  <drow@mvista.com>
+
 	* configure.in: Set insn=nop for DWARF-2 tests on ARM.
 	* configure: Regenerated.
 
diff --git a/gcc/gcc.c b/gcc/gcc.c
index c30851dfe17..a193437c569 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -267,11 +267,6 @@ static struct rusage rus, prus;
 struct path_prefix;
 
 static void init_spec		PARAMS ((void));
-#ifndef VMS
-static char **split_directories	PARAMS ((const char *, int *));
-static void free_split_directories PARAMS ((char **));
-static char *make_relative_prefix PARAMS ((const char *, const char *, const char *));
-#endif /* VMS */
 static void store_arg		PARAMS ((const char *, int, int));
 static char *load_specs		PARAMS ((const char *));
 static void read_specs		PARAMS ((const char *, int));
@@ -2281,246 +2276,6 @@ putenv_from_prefixes (paths, env_var)
   putenv (build_search_list (paths, env_var, 1));
 }
 
-#ifndef VMS
-
-/* FIXME: the location independence code for VMS is hairier than this,
-   and hasn't been written.  */
-
-/* Split a filename into component directories.  */
-
-static char **
-split_directories (name, ptr_num_dirs)
-     const char *name;
-     int *ptr_num_dirs;
-{
-  int num_dirs = 0;
-  char **dirs;
-  const char *p, *q;
-  int ch;
-
-  /* Count the number of directories.  Special case MSDOS disk names as part
-     of the initial directory.  */
-  p = name;
-#ifdef HAVE_DOS_BASED_FILE_SYSTEM
-  if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
-    {
-      p += 3;
-      num_dirs++;
-    }
-#endif /* HAVE_DOS_BASED_FILE_SYSTEM */
-
-  while ((ch = *p++) != '\0')
-    {
-      if (IS_DIR_SEPARATOR (ch))
-	{
-	  num_dirs++;
-	  while (IS_DIR_SEPARATOR (*p))
-	    p++;
-	}
-    }
-
-  dirs = (char **) xmalloc (sizeof (char *) * (num_dirs + 2));
-
-  /* Now copy the directory parts.  */
-  num_dirs = 0;
-  p = name;
-#ifdef HAVE_DOS_BASED_FILE_SYSTEM
-  if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
-    {
-      dirs[num_dirs++] = save_string (p, 3);
-      p += 3;
-    }
-#endif /* HAVE_DOS_BASED_FILE_SYSTEM */
-
-  q = p;
-  while ((ch = *p++) != '\0')
-    {
-      if (IS_DIR_SEPARATOR (ch))
-	{
-	  while (IS_DIR_SEPARATOR (*p))
-	    p++;
-
-	  dirs[num_dirs++] = save_string (q, p - q);
-	  q = p;
-	}
-    }
-
-  if (p - 1 - q > 0)
-    dirs[num_dirs++] = save_string (q, p - 1 - q);
-
-  dirs[num_dirs] = NULL;
-  if (ptr_num_dirs)
-    *ptr_num_dirs = num_dirs;
-
-  return dirs;
-}
-
-/* Release storage held by split directories.  */
-
-static void
-free_split_directories (dirs)
-     char **dirs;
-{
-  int i = 0;
-
-  while (dirs[i] != NULL)
-    free (dirs[i++]);
-
-  free ((char *) dirs);
-}
-
-/* Given three strings PROGNAME, BIN_PREFIX, PREFIX, return a string that gets
-   to PREFIX starting with the directory portion of PROGNAME and a relative
-   pathname of the difference between BIN_PREFIX and PREFIX.
-
-   For example, if BIN_PREFIX is /alpha/beta/gamma/gcc/delta, PREFIX is
-   /alpha/beta/gamma/omega/, and PROGNAME is /red/green/blue/gcc, then this
-   function will return /red/green/blue/../omega.
-
-   If no relative prefix can be found, return NULL.  */
-
-static char *
-make_relative_prefix (progname, bin_prefix, prefix)
-     const char *progname;
-     const char *bin_prefix;
-     const char *prefix;
-{
-  char **prog_dirs, **bin_dirs, **prefix_dirs;
-  int prog_num, bin_num, prefix_num, std_loc_p;
-  int i, n, common;
-
-  prog_dirs = split_directories (progname, &prog_num);
-  bin_dirs = split_directories (bin_prefix, &bin_num);
-
-  /* If there is no full pathname, try to find the program by checking in each
-     of the directories specified in the PATH environment variable.  */
-  if (prog_num == 1)
-    {
-      char *temp;
-
-      GET_ENVIRONMENT (temp, "PATH");
-      if (temp)
-	{
-	  char *startp, *endp, *nstore;
-	  size_t prefixlen = strlen (temp) + 1;
-	  if (prefixlen < 2)
-	    prefixlen = 2;
-
-	  nstore = (char *) alloca (prefixlen + strlen (progname) + 1);
-
-	  startp = endp = temp;
-	  while (1)
-	    {
-	      if (*endp == PATH_SEPARATOR || *endp == 0)
-		{
-		  if (endp == startp)
-		    {
-		      nstore[0] = '.';
-		      nstore[1] = DIR_SEPARATOR;
-		      nstore[2] = '\0';
-		    }
-		  else
-		    {
-		      strncpy (nstore, startp, endp - startp);
-		      if (! IS_DIR_SEPARATOR (endp[-1]))
-			{
-			  nstore[endp - startp] = DIR_SEPARATOR;
-			  nstore[endp - startp + 1] = 0;
-			}
-		      else
-			nstore[endp - startp] = 0;
-		    }
-		  strcat (nstore, progname);
-		  if (! access (nstore, X_OK)
-#ifdef HAVE_HOST_EXECUTABLE_SUFFIX
-                      || ! access (strcat (nstore, HOST_EXECUTABLE_SUFFIX), X_OK)
-#endif
-		      )
-		    {
-		      free_split_directories (prog_dirs);
-		      progname = nstore;
-		      prog_dirs = split_directories (progname, &prog_num);
-		      break;
-		    }
-
-		  if (*endp == 0)
-		    break;
-		  endp = startp = endp + 1;
-		}
-	      else
-		endp++;
-	    }
-	}
-    }
-
-  /* Remove the program name from comparison of directory names.  */
-  prog_num--;
-
-  /* Determine if the compiler is installed in the standard location, and if
-     so, we don't need to specify relative directories.  Also, if argv[0]
-     doesn't contain any directory specifiers, there is not much we can do.  */
-  std_loc_p = 0;
-  if (prog_num == bin_num)
-    {
-      for (i = 0; i < bin_num; i++)
-	{
-	  if (strcmp (prog_dirs[i], bin_dirs[i]) != 0)
-	    break;
-	}
-
-      if (prog_num <= 0 || i == bin_num)
-	{
-	  std_loc_p = 1;
-	  free_split_directories (prog_dirs);
-	  free_split_directories (bin_dirs);
-	  prog_dirs = bin_dirs = (char **) 0;
-	  return NULL;
-	}
-    }
-
-  prefix_dirs = split_directories (prefix, &prefix_num);
-
-  /* Find how many directories are in common between bin_prefix & prefix.  */
-  n = (prefix_num < bin_num) ? prefix_num : bin_num;
-  for (common = 0; common < n; common++)
-    {
-      if (strcmp (bin_dirs[common], prefix_dirs[common]) != 0)
-	break;
-    }
-
-  /* If there are no common directories, there can be no relative prefix.  */
-  if (common == 0)
-    {
-      free_split_directories (prog_dirs);
-      free_split_directories (bin_dirs);
-      free_split_directories (prefix_dirs);
-      return NULL;
-    }
-
-  /* Build up the pathnames in argv[0].  */
-  for (i = 0; i < prog_num; i++)
-    obstack_grow (&obstack, prog_dirs[i], strlen (prog_dirs[i]));
-
-  /* Now build up the ..'s.  */
-  for (i = common; i < n; i++)
-    {
-      obstack_grow (&obstack, DIR_UP, sizeof (DIR_UP) - 1);
-      obstack_1grow (&obstack, DIR_SEPARATOR);
-    }
-
-  /* Put in directories to move over to prefix.  */
-  for (i = common; i < prefix_num; i++)
-    obstack_grow (&obstack, prefix_dirs[i], strlen (prefix_dirs[i]));
-
-  free_split_directories (prog_dirs);
-  free_split_directories (bin_dirs);
-  free_split_directories (prefix_dirs);
-
-  obstack_1grow (&obstack, '\0');
-  return obstack_finish (&obstack);
-}
-#endif /* VMS */
-
 /* Check whether NAME can be accessed in MODE.  This is like access,
    except that it never considers directories to be executable.  */
 
diff --git a/include/ChangeLog b/include/ChangeLog
index 2eaa1fd2d69..ea9575351f5 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,7 @@
+2002-11-22  Daniel Jacobowitz  <drow@mvista.com>
+
+	* libiberty.h (make_relative_prefix): Add prototype.
+
 2002-10-26  Roger Sayle  <roger@eyesopen.com>
 
 	* partition.h:  Close the extern "C" scope when compiling with C++.
diff --git a/include/libiberty.h b/include/libiberty.h
index 983fd96e5ae..c02e035e3af 100644
--- a/include/libiberty.h
+++ b/include/libiberty.h
@@ -145,6 +145,12 @@ extern char * getpwd PARAMS ((void));
 
 extern long get_run_time PARAMS ((void));
 
+/* Generate a relocated path to some installation directory.  Allocates
+   return value using malloc.  */
+
+extern char *make_relative_prefix PARAMS ((const char *, const char *,
+					   const char *));
+
 /* Choose a temporary directory to use for scratch files.  */
 
 extern char *choose_temp_base PARAMS ((void)) ATTRIBUTE_MALLOC;
diff --git a/libiberty/ChangeLog b/libiberty/ChangeLog
index 8966e2ee867..57ff7da31b5 100644
--- a/libiberty/ChangeLog
+++ b/libiberty/ChangeLog
@@ -1,3 +1,9 @@
+2002-11-22  Daniel Jacobowitz  <drow@mvista.com>
+
+	* Makefile.in: Add make-relative-prefix.c.
+	* make-relative-prefix.c: New file.
+	* functions.texi: Rebuilt.
+
 2002-11-16  Jakub Jelinek  <jakub@redhat.com>
 
 	* md5.c (md5_process_block): Avoid `function-like macro "F{G,H,I}" must be
diff --git a/libiberty/Makefile.in b/libiberty/Makefile.in
index e0bb15a7519..cdf14a4311b 100644
--- a/libiberty/Makefile.in
+++ b/libiberty/Makefile.in
@@ -135,6 +135,7 @@ CFILES = alloca.c argv.c asprintf.c atexit.c				\
 	hashtab.c hex.c							\
 	index.c insque.c						\
 	lbasename.c							\
+	make-relative-prefix.c						\
 	make-temp-file.c md5.c memchr.c memcmp.c memcpy.c memmove.c	\
 	 memset.c mkstemps.c						\
 	objalloc.c obstack.c						\
@@ -159,6 +160,7 @@ REQUIRED_OFILES = regex.o cplus-dem.o cp-demangle.o md5.o		\
 	getopt.o getopt1.o getpwd.o getruntime.o			\
 	hashtab.o hex.o							\
 	lbasename.o							\
+	make-relative-prefix.o						\
 	make-temp-file.o						\
 	objalloc.o obstack.o						\
 	partition.o pexecute.o						\
@@ -432,6 +434,7 @@ hashtab.o: config.h $(INCDIR)/ansidecl.h $(INCDIR)/hashtab.h \
 hex.o: $(INCDIR)/ansidecl.h $(INCDIR)/libiberty.h
 lbasename.o: $(INCDIR)/ansidecl.h $(INCDIR)/libiberty.h \
 	$(INCDIR)/safe-ctype.h
+make-relative-prefix.o: config.h $(INCDIR)/ansidecl.h $(INCDIR)/libiberty.h
 make-temp-file.o: config.h $(INCDIR)/ansidecl.h $(INCDIR)/libiberty.h
 md5.o: config.h $(INCDIR)/ansidecl.h $(INCDIR)/md5.h
 memchr.o: $(INCDIR)/ansidecl.h
diff --git a/libiberty/functions.texi b/libiberty/functions.texi
index b518243d95a..7d9c181d219 100644
--- a/libiberty/functions.texi
+++ b/libiberty/functions.texi
@@ -276,7 +276,7 @@ itself.
 
 @end deftypefn
 
-@c getruntime.c:78
+@c getruntime.c:82
 @deftypefn Replacement long get_run_time (void)
 
 Returns the time used so far, in microseconds.  If possible, this is
@@ -322,11 +322,12 @@ between calls to @code{getpwd}.
 
 Initializes the array mapping the current character set to
 corresponding hex values.  This function must be called before any
-call to @code{hex_p} or @code{hex_value}.
+call to @code{hex_p} or @code{hex_value}.  If you fail to call it, a
+default ASCII-based table will normally be used on ASCII systems.
 
 @end deftypefn
 
-@c hex.c:33
+@c hex.c:34
 @deftypefn Extension int hex_p (int @var{c})
 
 Evaluates to non-zero if the given character is a valid hex character,
@@ -335,7 +336,7 @@ or zero if it is not.  Note that the value you pass will be cast to
 
 @end deftypefn
 
-@c hex.c:41
+@c hex.c:42
 @deftypefn Extension int hex_value (int @var{c})
 
 Returns the numeric equivalent of the given character when interpreted
@@ -391,6 +392,22 @@ and a path ending in @code{/} returns the empty string after it.
 
 @end deftypefn
 
+@c make-relative-prefix.c:24
+@deftypefn Extension {const char*} make_relative_prefix (const char *@var{progname}, const char *@var{bin_prefix}, const char *@var{prefix})
+
+Given three strings @var{progname}, @var{bin_prefix}, @var{prefix}, return a string
+that gets to @var{prefix} starting with the directory portion of @var{progname} and
+a relative pathname of the difference between @var{bin_prefix} and @var{prefix}.
+
+For example, if @var{bin_prefix} is @code{/alpha/beta/gamma/gcc/delta}, @var{prefix}
+is @code{/alpha/beta/gamma/omega/}, and @var{progname} is @code{/red/green/blue/gcc},
+then this function will return @code{/red/green/blue/../../omega/}.
+
+The return value is normally allocated via @code{malloc}.  If no relative prefix
+can be found, return @code{NULL}.
+
+@end deftypefn
+
 @c make-temp-file.c:138
 @deftypefn Replacement char* make_temp_file (const char *@var{suffix})
 
diff --git a/libiberty/make-relative-prefix.c b/libiberty/make-relative-prefix.c
new file mode 100644
index 00000000000..ae1ac54295a
--- /dev/null
+++ b/libiberty/make-relative-prefix.c
@@ -0,0 +1,387 @@
+/* Relative (relocatable) prefix support.
+   Copyright (C) 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
+   1999, 2000, 2001, 2002 Free Software Foundation, Inc.
+
+This file is part of libiberty.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING.  If not, write to the Free
+Software Foundation, 59 Temple Place - Suite 330, Boston, MA
+02111-1307, USA.  */
+
+/*
+
+@deftypefn Extension {const char*} make_relative_prefix (const char *@var{progname}, const char *@var{bin_prefix}, const char *@var{prefix})
+
+Given three strings @var{progname}, @var{bin_prefix}, @var{prefix}, return a string
+that gets to @var{prefix} starting with the directory portion of @var{progname} and
+a relative pathname of the difference between @var{bin_prefix} and @var{prefix}.
+
+For example, if @var{bin_prefix} is @code{/alpha/beta/gamma/gcc/delta}, @var{prefix}
+is @code{/alpha/beta/gamma/omega/}, and @var{progname} is @code{/red/green/blue/gcc},
+then this function will return @code{/red/green/blue/../../omega/}.
+
+The return value is normally allocated via @code{malloc}.  If no relative prefix
+can be found, return @code{NULL}.
+
+@end deftypefn
+
+*/
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+#include <string.h>
+
+#include "ansidecl.h"
+#include "libiberty.h"
+
+#ifndef R_OK
+#define R_OK 4
+#define W_OK 2
+#define X_OK 1
+#endif
+
+#ifndef DIR_SEPARATOR
+#  define DIR_SEPARATOR '/'
+#endif
+
+#if defined (_WIN32) || defined (__MSDOS__) \
+    || defined (__DJGPP__) || defined (__OS2__)
+#  define HAVE_DOS_BASED_FILE_SYSTEM
+#  define HOST_EXECUTABLE_SUFFIX ".exe"
+#  ifndef DIR_SEPARATOR_2 
+#    define DIR_SEPARATOR_2 '\\'
+#  endif
+#  define PATH_SEPARATOR ';'
+#else
+#  define PATH_SEPARATOR ':'
+#endif
+
+#ifndef DIR_SEPARATOR_2
+#  define IS_DIR_SEPARATOR(ch) ((ch) == DIR_SEPARATOR)
+#else
+#  define IS_DIR_SEPARATOR(ch) \
+	(((ch) == DIR_SEPARATOR) || ((ch) == DIR_SEPARATOR_2))
+#endif
+
+#define DIR_UP ".."
+
+static char *save_string PARAMS ((const char *, int));
+static char **split_directories	PARAMS ((const char *, int *));
+static void free_split_directories PARAMS ((char **));
+
+static char *
+save_string (s, len)
+     const char *s;
+     int len;
+{
+  char *result = malloc (len + 1);
+
+  memcpy (result, s, len);
+  result[len] = 0;
+  return result;
+}
+
+/* Split a filename into component directories.  */
+
+static char **
+split_directories (name, ptr_num_dirs)
+     const char *name;
+     int *ptr_num_dirs;
+{
+  int num_dirs = 0;
+  char **dirs;
+  const char *p, *q;
+  int ch;
+
+  /* Count the number of directories.  Special case MSDOS disk names as part
+     of the initial directory.  */
+  p = name;
+#ifdef HAVE_DOS_BASED_FILE_SYSTEM
+  if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
+    {
+      p += 3;
+      num_dirs++;
+    }
+#endif /* HAVE_DOS_BASED_FILE_SYSTEM */
+
+  while ((ch = *p++) != '\0')
+    {
+      if (IS_DIR_SEPARATOR (ch))
+	{
+	  num_dirs++;
+	  while (IS_DIR_SEPARATOR (*p))
+	    p++;
+	}
+    }
+
+  dirs = (char **) malloc (sizeof (char *) * (num_dirs + 2));
+  if (dirs == NULL)
+    return NULL;
+
+  /* Now copy the directory parts.  */
+  num_dirs = 0;
+  p = name;
+#ifdef HAVE_DOS_BASED_FILE_SYSTEM
+  if (name[1] == ':' && IS_DIR_SEPARATOR (name[2]))
+    {
+      dirs[num_dirs++] = save_string (p, 3);
+      if (dirs[num_dirs - 1] == NULL)
+	{
+	  free (dirs);
+	  return NULL;
+	}
+      p += 3;
+    }
+#endif /* HAVE_DOS_BASED_FILE_SYSTEM */
+
+  q = p;
+  while ((ch = *p++) != '\0')
+    {
+      if (IS_DIR_SEPARATOR (ch))
+	{
+	  while (IS_DIR_SEPARATOR (*p))
+	    p++;
+
+	  dirs[num_dirs++] = save_string (q, p - q);
+	  if (dirs[num_dirs - 1] == NULL)
+	    {
+	      dirs[num_dirs] = NULL;
+	      free_split_directories (dirs);
+	      return NULL;
+	    }
+	  q = p;
+	}
+    }
+
+  if (p - 1 - q > 0)
+    dirs[num_dirs++] = save_string (q, p - 1 - q);
+  dirs[num_dirs] = NULL;
+
+  if (dirs[num_dirs - 1] == NULL)
+    {
+      free_split_directories (dirs);
+      return NULL;
+    }
+
+  if (ptr_num_dirs)
+    *ptr_num_dirs = num_dirs;
+  return dirs;
+}
+
+/* Release storage held by split directories.  */
+
+static void
+free_split_directories (dirs)
+     char **dirs;
+{
+  int i = 0;
+
+  while (dirs[i] != NULL)
+    free (dirs[i++]);
+
+  free ((char *) dirs);
+}
+
+/* Given three strings PROGNAME, BIN_PREFIX, PREFIX, return a string that gets
+   to PREFIX starting with the directory portion of PROGNAME and a relative
+   pathname of the difference between BIN_PREFIX and PREFIX.
+
+   For example, if BIN_PREFIX is /alpha/beta/gamma/gcc/delta, PREFIX is
+   /alpha/beta/gamma/omega/, and PROGNAME is /red/green/blue/gcc, then this
+   function will return /red/green/blue/../../omega/.
+
+   If no relative prefix can be found, return NULL.  */
+
+char *
+make_relative_prefix (progname, bin_prefix, prefix)
+     const char *progname;
+     const char *bin_prefix;
+     const char *prefix;
+{
+  char **prog_dirs, **bin_dirs, **prefix_dirs;
+  int prog_num, bin_num, prefix_num;
+  int i, n, common;
+  int needed_len;
+  char *ret, *ptr;
+
+  if (progname == NULL || bin_prefix == NULL || prefix == NULL)
+    return NULL;
+
+  prog_dirs = split_directories (progname, &prog_num);
+  bin_dirs = split_directories (bin_prefix, &bin_num);
+  if (bin_dirs == NULL || prog_dirs == NULL)
+    return NULL;
+
+  /* If there is no full pathname, try to find the program by checking in each
+     of the directories specified in the PATH environment variable.  */
+  if (prog_num == 1)
+    {
+      char *temp;
+
+      temp = getenv ("PATH");
+      if (temp)
+	{
+	  char *startp, *endp, *nstore;
+	  size_t prefixlen = strlen (temp) + 1;
+	  if (prefixlen < 2)
+	    prefixlen = 2;
+
+	  nstore = (char *) alloca (prefixlen + strlen (progname) + 1);
+
+	  startp = endp = temp;
+	  while (1)
+	    {
+	      if (*endp == PATH_SEPARATOR || *endp == 0)
+		{
+		  if (endp == startp)
+		    {
+		      nstore[0] = '.';
+		      nstore[1] = DIR_SEPARATOR;
+		      nstore[2] = '\0';
+		    }
+		  else
+		    {
+		      strncpy (nstore, startp, endp - startp);
+		      if (! IS_DIR_SEPARATOR (endp[-1]))
+			{
+			  nstore[endp - startp] = DIR_SEPARATOR;
+			  nstore[endp - startp + 1] = 0;
+			}
+		      else
+			nstore[endp - startp] = 0;
+		    }
+		  strcat (nstore, progname);
+		  if (! access (nstore, X_OK)
+#ifdef HAVE_HOST_EXECUTABLE_SUFFIX
+                      || ! access (strcat (nstore, HOST_EXECUTABLE_SUFFIX), X_OK)
+#endif
+		      )
+		    {
+		      free_split_directories (prog_dirs);
+		      progname = nstore;
+		      prog_dirs = split_directories (progname, &prog_num);
+		      if (prog_dirs == NULL)
+			{
+			  free_split_directories (bin_dirs);
+			  return NULL;
+			}
+		      break;
+		    }
+
+		  if (*endp == 0)
+		    break;
+		  endp = startp = endp + 1;
+		}
+	      else
+		endp++;
+	    }
+	}
+    }
+
+  /* Remove the program name from comparison of directory names.  */
+  prog_num--;
+
+  /* If we are still installed in the standard location, we don't need to
+     specify relative directories.  Also, if argv[0] still doesn't contain
+     any directory specifiers after the search above, then there is not much
+     we can do.  */
+  if (prog_num == bin_num)
+    {
+      for (i = 0; i < bin_num; i++)
+	{
+	  if (strcmp (prog_dirs[i], bin_dirs[i]) != 0)
+	    break;
+	}
+
+      if (prog_num <= 0 || i == bin_num)
+	{
+	  free_split_directories (prog_dirs);
+	  free_split_directories (bin_dirs);
+	  prog_dirs = bin_dirs = (char **) 0;
+	  return NULL;
+	}
+    }
+
+  prefix_dirs = split_directories (prefix, &prefix_num);
+  if (prefix_dirs == NULL)
+    {
+      free_split_directories (prog_dirs);
+      free_split_directories (bin_dirs);
+      return NULL;
+    }
+
+  /* Find how many directories are in common between bin_prefix & prefix.  */
+  n = (prefix_num < bin_num) ? prefix_num : bin_num;
+  for (common = 0; common < n; common++)
+    {
+      if (strcmp (bin_dirs[common], prefix_dirs[common]) != 0)
+	break;
+    }
+
+  /* If there are no common directories, there can be no relative prefix.  */
+  if (common == 0)
+    {
+      free_split_directories (prog_dirs);
+      free_split_directories (bin_dirs);
+      free_split_directories (prefix_dirs);
+      return NULL;
+    }
+
+  /* Two passes: first figure out the size of the result string, and
+     then construct it.  */
+  needed_len = 0;
+  for (i = 0; i < prog_num; i++)
+    needed_len += strlen (prog_dirs[i]);
+  needed_len += sizeof (DIR_UP) * (bin_num - common);
+  for (i = common; i < prefix_num; i++)
+    needed_len += strlen (prefix_dirs[i]);
+  needed_len += 1; /* Trailing NUL.  */
+
+  ret = (char *) malloc (needed_len);
+  if (ret == NULL)
+    return NULL;
+
+  /* Build up the pathnames in argv[0].  */
+  for (i = 0; i < prog_num; i++)
+    strcat (ret, prog_dirs[i]);
+
+  /* Now build up the ..'s.  */
+  ptr = ret + strlen(ret);
+  for (i = common; i < bin_num; i++)
+    {
+      strcpy (ptr, DIR_UP);
+      ptr += sizeof (DIR_UP) - 1;
+      *(ptr++) = DIR_SEPARATOR;
+    }
+  *ptr = '\0';
+
+  /* Put in directories to move over to prefix.  */
+  for (i = common; i < prefix_num; i++)
+    strcat (ret, prefix_dirs[i]);
+
+  free_split_directories (prog_dirs);
+  free_split_directories (bin_dirs);
+  free_split_directories (prefix_dirs);
+
+  return ret;
+}