Re: [PATCH] PR fortran/84734 -- Fix ICE on invalid code

[Steve Kargl <sgk@troutmask.apl.washington.edu>]

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On Fri, Mar 09, 2018 at 09:13:10PM -0800, Steve Kargl wrote:
> In fixing PR fortran/83633, it seems the patch I committed
> introduced an ICE for nonsensical invalid Fortran.  The 
> attached patch cures the ICE and now (re)issues an error
> message.
> 
> The basic problem seems to boil down to the recursive 
> calling of gfc_simplify_expr reduces "huge(1_8)+1_8" to
> "constant + constant".  When the chain of gfc_simplify_expr
> tries to reduces this expression an overflow occurs.  An
> error message is queud but never emitted, and the result
> is set to NULL and both constants are freed.  The NULL is
> passed back up through the chain of gfc_simplify_expr.
> At some point that NULL pointer is referenced.  The patch
> works around the problem by passing the result with the
> overflow value up the chain.  
> 
> Regression tested on x86_64-*-freebsd.  I intend to commit
> this patch tomorrow, which on my clock is only 2.75 hours
> away.
> 
> 2018-03-09  Steven G. Kargl  <kargl@gcc.gnu.org>
> 
>         PR fortran/84734
>         * arith.c (check_result, eval_intrinsic):  If result overflows, pass
>         the expression up the chain instead of a NULL pointer.
> 
> 2018-03-09  Steven G. Kargl  <kargl@gcc.gnu.org>
> 
>         PR fortran/84734
>         * gfortran.dg/pr84734.f90: New test.
> 

Now with an attached patch.

-- 
Steve

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Index: gcc/fortran/arith.c
===================================================================
--- gcc/fortran/arith.c	(revision 258367)
+++ gcc/fortran/arith.c	(working copy)
@@ -555,10 +555,10 @@ check_result (arith rc, gfc_expr *x, gfc_expr *r, gfc_
       val = ARITH_OK;
     }
 
-  if (val != ARITH_OK)
-    gfc_free_expr (r);
-  else
+  if (val == ARITH_OK || val == ARITH_OVERFLOW)
     *rp = r;
+  else
+    gfc_free_expr (r);
 
   return val;
 }
@@ -1603,8 +1603,12 @@ eval_intrinsic (gfc_intrinsic_op op,
   if (rc != ARITH_OK)
     {
       gfc_error (gfc_arith_error (rc), &op1->where);
+      if (rc == ARITH_OVERFLOW)
+	goto done;
       return NULL;
     }
+
+done:
 
   gfc_free_expr (op1);
   gfc_free_expr (op2);
Index: gcc/testsuite/gfortran.dg/pr84734.f90
===================================================================
--- gcc/testsuite/gfortran.dg/pr84734.f90	(nonexistent)
+++ gcc/testsuite/gfortran.dg/pr84734.f90	(working copy)
@@ -0,0 +1,4 @@
+! { dg-do compile }
+! PR fortran/84734
+   integer :: b(huge(1_8)+1_8) = 0 ! { dg-error "Arithmetic overflow" }
+   end