Re: gdb/417: GDB crashes when source path has few links

["Michael Veksler" <VEKSLER at il dot ibm dot com>]

The following reply was made to PR gdb/417; it has been noted by GNATS.

From: "Michael Veksler" <VEKSLER@il.ibm.com>
To: Andrew Cagney <ac131313@cygnus.com>
Cc: gdb-gnats@sources.redhat.com
Subject: Re: gdb/417: GDB crashes when source path has few links
Date: Sun, 17 Mar 2002 10:29:49 +0200

 Andrew wrote:
 > >(ulgh, two different bug reports against the same 3 line patch :-).
 
 Which one? I scanned the database, and could not find any similar bug.
 
 I worte (Michael Veksler):
 > > Sometimes gdb crashes when it tries to display sources.
 > >
 > > open_source_file() calls openp() which assumes that if open() succeeds
 so
 > > does canonicalize_file_name(). After openp() succeeded to open the
 file,
 > > open_source_file() assumes that it has a canonic file name. But this
 > > assumption is incorrect.
 >
 
 > Does modifying utils.c to use realpath() instead of
 > canonicalize_file_name() provide a tempoary work around to the problem?
 > (I suspect not but might be worth a try).
 My 3 lines patch fixes the problem:
 --- gdb+dejagnu-5.1.90_20020313/gdb/utils.c.orig        Thu Mar 14 10:06:02
 2002
 +++ gdb+dejagnu-5.1.90_20020313/gdb/utils.c     Thu Mar 14 10:07:56 2002
 @@ -2533,7 +2533,8 @@
  gdb_realpath (const char *filename)
  {
  #ifdef HAVE_CANONICALIZE_FILE_NAME
 -  return canonicalize_file_name (filename);
 +  char *canonic= canonicalize_file_name (filename);
 +  return (canonic ? canonic : xstrdup(filename));
  #elif defined (HAVE_REALPATH)
  #if defined (PATH_MAX)
    char buf[PATH_MAX];
 
 It simply performs the same check that the call to realpath does. If the
 result
 is NULL, then return the original filename. Probably, if you will undef
 HAVE_CANONICALIZE_FILE_NAME, then everything will work fine, because the
 call
 realpath implements the check for NULL.
 
 > (NB: need to also check that canonicalize_file_name() allocates space
 > from the heap.)
 
 It does.
 You can look at:
 
 1. Documentation:
 http://www.gnu.org/manual/glibc-2.2.3/html_node/libc_269.html
 
 2. Source:
 http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/libc/stdlib/canonicalize.c?rev=1.19&content-type=text/plain&cvsroot=glibc
 
 realpath() is implemented by the same code as canonicalize_file_name() is.
 Except for malloc()-ing the string buffer they are the same function.
 Allocation is performed by:
 
 #ifdef PATH_MAX
   path_max = PATH_MAX;
 #else
   path_max = pathconf (name, _PC_PATH_MAX);
   if (path_max <= 0)
     path_max = 1024;
 #endif
 
   malloc (path_max)