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From: =?iso-8859-1?Q?Pop_S=E9bastian?= <pop@gauvain.u-strasbg.fr>
Subject: Re: c++/7754: ICE SIGSEGV on union with template parameter
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The following reply was made to PR c++/7754; it has been noted by GNATS.

From: =?iso-8859-1?Q?Pop_S=E9bastian?= <pop@gauvain.u-strasbg.fr>
To: nathan@gcc.gnu.org, dv@vollmann.ch, gcc-bugs@gcc.gnu.org,
	gcc-prs@gcc.gnu.org, nobody@gcc.gnu.org, gcc-gnats@gcc.gnu.org
Cc: aoliva@redhat.com
Subject: Re: c++/7754: ICE SIGSEGV on union with template parameter
Date: Sun, 29 Sep 2002 10:29:05 +0200

 On Fri, Sep 13, 2002 at 09:04:23PM -0000, nathan@gcc.gnu.org wrote:
 > Synopsis: ICE SIGSEGV on union with template parameter
 > 
 > State-Changed-From-To: open->analyzed
 > State-Changed-By: nathan
 > State-Changed-When: Fri Sep 13 14:04:22 2002
 > State-Changed-Why:
 >     confirmed as a regression
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7754
 
 SIGSEGV happens in tree.c:
 
 /* Nonzero if integer constants T1 and T2 represent values that satisfy <.
    The precise way of comparison depends on their data type.  */
 
 int
 tree_int_cst_lt (t1, t2)
      tree t1, t2;
 {
   if (t1 == t2)
     return 0;
 
 =>if (TREE_UNSIGNED (TREE_TYPE (t1)) != TREE_UNSIGNED (TREE_TYPE (t2)))
     {
       int t1_sgn = tree_int_cst_sgn (t1);
       int t2_sgn = tree_int_cst_sgn (t2);
 
       if (t1_sgn < t2_sgn)
         return 1;
       else if (t1_sgn > t2_sgn)
         return 0;
       /* Otherwise, both are non-negative, so we compare them as
          unsigned just in case one of them would overflow a signed
          type.  */
     }
   else if (! TREE_UNSIGNED (TREE_TYPE (t1)))
     return INT_CST_LT (t1, t2);
 
   return INT_CST_LT_UNSIGNED (t1, t2);
 }
 
 
 At this point t2 is equal to 0, and that crashes the compiler.
 
 The following patch introduced this code without checking of non-NULL for t2:
 
 2002-04-26  Alexandre Oliva  <aoliva@redhat.com>
 http://gcc.gnu.org/ml/gcc-patches/2002-04/msg01549.html
 
 
 Alexandre, could you review this patch and the associated bug-report please?
 
 Thanks, 
 Sebastian