[PATCH] Fix make_relative_prefix_1 (PR driver/48306)

[Jakub Jelinek]

Hi!

As reported in the PR, when the gcc (or g++, ...) binary
is not started with full path and somewhere in $PATH earlier
then were gcc binary is is a directory with the same name (gcc, g++, ...),
then execvp will ignore it, but make_relative_prefix will think it
is the path to the driver and derive paths from that, thus likely won't be
able to find cc1 etc.

The following patch fixes it by skipping pathnames that aren't regular
files.  Unfortunately it adds an extra syscall for each path element
successfully statted.  For Linux we could perhaps do better, if
we
#ifdef __linux__
  ssize_t len = readlink ("/proc/self/exe", buf, sizeof buf);
  if (len > 0 && len < sizeof buf)
    {
      buf[len] = '\0';
      /* Executable filename is in buf, goto somewhere and
         skip the $PATH loop.  */
    }
#endif
but would need to do some portability hacks for that.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2011-12-21  Jakub Jelinek  <ja...@redhat.com>

        * make-relative-prefix.c (make_relative_prefix_1): Avoid
        stack overflow if PATH contains just a single entry and
        HOST_EXECUTABLE_SUFFIX needs to be used.

        PR driver/48306
        * make-relative-prefix.c: Include sys/stat.h.
        (make_relative_prefix_1): If access succeeds, check also stat
        if nstore is a regular file.

--- libiberty/make-relative-prefix.c.jj 2011-02-15 15:40:07.000000000 +0100
+++ libiberty/make-relative-prefix.c    2011-12-19 20:47:02.613081452 +0100
@@ -1,6 +1,6 @@
 /* Relative (relocatable) prefix support.
    Copyright (C) 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2006 Free Software Foundation, Inc.
+   1999, 2000, 2001, 2002, 2006, 2011 Free Software Foundation, Inc.
 
 This file is part of libiberty.
 
@@ -58,6 +58,9 @@ relative prefix can be found, return @co
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
+#ifdef HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
 
 #include <string.h>
 
@@ -248,7 +251,11 @@ make_relative_prefix_1 (const char *prog
          if (prefixlen < 2)
            prefixlen = 2;
 
-         nstore = (char *) alloca (prefixlen + strlen (progname) + 1);
+         nstore = (char *) alloca (prefixlen + strlen (progname) + 1
+#ifdef HAVE_HOST_EXECUTABLE_SUFFIX
+                                   + strlen (HOST_EXECUTABLE_SUFFIX)
+#endif
+                                   );
 
          startp = endp = temp;
          while (1)
@@ -263,7 +270,7 @@ make_relative_prefix_1 (const char *prog
                    }
                  else
                    {
-                     strncpy (nstore, startp, endp - startp);
+                     memcpy (nstore, startp, endp - startp);
                      if (! IS_DIR_SEPARATOR (endp[-1]))
                        {
                          nstore[endp - startp] = DIR_SEPARATOR;
@@ -279,8 +286,14 @@ make_relative_prefix_1 (const char *prog
 #endif
                      )
                    {
-                     progname = nstore;
-                     break;
+#if defined (HAVE_SYS_STAT_H) && defined (S_ISREG)
+                     struct stat st;
+                     if (stat (nstore, &st) >= 0 && S_ISREG (st.st_mode))
+#endif
+                       {
+                         progname = nstore;
+                         break;
+                       }
                    }
 
                  if (*endp == 0)

        Jakub