Re: [Patch, fortran, GCC-5/6, PR62536, v1] ICE (segfault) for invalid END BLOCK statement

[Andre Vehreschild <vehre at gmx dot de>]

Hi Jerry, hi all,

thanks for the fast review. Committed as

r232918 for gcc-5-branch, and

r232919 for trunk.

Thanks again Jerry and regards,

	Andre

On Wed, 27 Jan 2016 15:19:32 -0800
Jerry DeLisle <jvdelisle@charter.net> wrote:

> On 01/27/2016 08:25 AM, Andre Vehreschild wrote:
> > Hi all,
> > 
> > attached are two patches one for trunk and one for the gcc-5-branch,
> > which fix an ICE when BLOCK statements are not closed correctly (too
> > many END BLOCKs). Unfortunately did the patch I tailored for gcc-5 not
> > work on trunk.
> > 
> > GCC 5: The ICE is prevented by making sure that gfc_current_ns is not
> > set to NULL, when too many closing END BLOCK statements are found. This
> > may lead to gfortran be in the wrong namespace, but gfortran is already
> > in error. Therefore this does not matter any more. We just need to exit
> > cleanly.
> > 
> > GCC 6/trunk: Here the ICE is prevented by making sure, that unnesting
> > of BLOCK namespaces is only done, when the END encountered is not the
> > one of a BLOCK. This prevents gfortran from removing a correctly
> > initialized and for further analysis required namespace.
> > 
> > Bootstrapped and regtested ok on x86_64-linux-gnu/F23. 
> > 
> > Ok for trunk and gcc-5-branch, respectively?
> >   
> 
> OK and thanks for fixes. Much appreciated?
> 
> Jerry


-- 
Andre Vehreschild * Email: vehre ad gmx dot de 

Index: gcc/fortran/ChangeLog
===================================================================
--- gcc/fortran/ChangeLog	(Revision 232916)
+++ gcc/fortran/ChangeLog	(Arbeitskopie)
@@ -1,3 +1,11 @@
+2016-01-28  Andre Vehreschild  <vehre@gcc.gnu.org>
+
+	PR fortran/62536
+	* decl.c: Prevent setting gfc_current_ns to NULL when block statement's
+	nesting is incomplete.  There is already an error conditon, so having
+	gfc_current_ns pointing to an eventually wrong namespace does not matter
+	that much.
+
 2016-01-27  Andre Vehreschild  <vehre@gcc.gnu.org>
 
 	PR fortran/p69268
Index: gcc/fortran/decl.c
===================================================================
--- gcc/fortran/decl.c	(Revision 232916)
+++ gcc/fortran/decl.c	(Arbeitskopie)
@@ -6454,9 +6454,16 @@
 	  prev_ns = ns;
 	  ns = ns->sibling;
 	}
-  
-      gfc_free_namespace (gfc_current_ns);
-      gfc_current_ns = parent_ns;
+
+      if (parent_ns)
+	{
+	  /* Free the current namespace only when the parent one exists.  This
+	     prevents an ICE when more END BLOCK then BLOCK statements are
+	     present.  It does not mean any further harm, because we already
+	     have errored.  */
+	  gfc_free_namespace (gfc_current_ns);
+	  gfc_current_ns = parent_ns;
+	}
     }
 
   return MATCH_ERROR;
Index: gcc/testsuite/ChangeLog
===================================================================
--- gcc/testsuite/ChangeLog	(Revision 232916)
+++ gcc/testsuite/ChangeLog	(Arbeitskopie)
@@ -1,3 +1,8 @@
+2016-01-28  Andre Vehreschild  <vehre@gcc.gnu.org>
+
+	PR fortran/62536
+	* gfortran.dg/block_14.f08: New test.
+
 2016-01-27  Marek Polacek  <polacek@redhat.com>
 
 	Backport from mainline

Index: gcc/fortran/ChangeLog
===================================================================
--- gcc/fortran/ChangeLog	(Revision 232917)
+++ gcc/fortran/ChangeLog	(Arbeitskopie)
@@ -1,3 +1,9 @@
+2016-01-28  Andre Vehreschild  <vehre@gcc.gnu.org>
+
+	PR fortran/62536
+	* decl.c (gfc_match_end): Only unnest and remove BLOCK namespaces
+	when the END encountered does not match a BLOCK's end.
+
 2016-01-27  Janus Weil  <janus@gcc.gnu.org>
 
 	PR fortran/69484
Index: gcc/fortran/decl.c
===================================================================
--- gcc/fortran/decl.c	(Revision 232917)
+++ gcc/fortran/decl.c	(Arbeitskopie)
@@ -6327,6 +6327,7 @@
   gfc_namespace *parent_ns, *ns, *prev_ns;
   gfc_namespace **nsp;
   bool abreviated_modproc_decl;
+  bool got_matching_end = false;
 
   old_loc = gfc_current_locus;
   if (gfc_match ("end") != MATCH_YES)
@@ -6510,6 +6511,8 @@
 		 ? "END PROCEDURE" : gfc_ascii_statement(*st), &old_loc);
       goto cleanup;
     }
+  else
+    got_matching_end = true;
 
   old_loc = gfc_current_locus;
   /* If we're at the end, make sure a block name wasn't required.  */
@@ -6581,7 +6584,7 @@
   /* If we are missing an END BLOCK, we created a half-ready namespace.
      Remove it from the parent namespace's sibling list.  */
 
-  while (state == COMP_BLOCK)
+  while (state == COMP_BLOCK && !got_matching_end)
     {
       parent_ns = gfc_current_ns->parent;
 
@@ -6601,7 +6604,7 @@
 	  prev_ns = ns;
 	  ns = ns->sibling;
 	}
-  
+
       gfc_free_namespace (gfc_current_ns);
       gfc_current_ns = parent_ns;
       gfc_state_stack = gfc_state_stack->previous;
Index: gcc/testsuite/ChangeLog
===================================================================
--- gcc/testsuite/ChangeLog	(Revision 232917)
+++ gcc/testsuite/ChangeLog	(Arbeitskopie)
@@ -1,3 +1,10 @@
+2016-01-28  Andre Vehreschild  <vehre@gcc.gnu.org>
+
+	PR fortran/62536
+	* gfortran.dg/block_15.f08: New test.
+	* gfortran.dg/block_end_error_1.f90: Need to catch additional error
+	on incorrectly closed BLOCK.
+
 2016-01-28  Ilya Enkovich  <enkovich.gnu@gmail.com>
 
 	* gcc.dg/declare-simd.c: New test.
Index: gcc/testsuite/gfortran.dg/block_end_error_1.f90
===================================================================
--- gcc/testsuite/gfortran.dg/block_end_error_1.f90	(Revision 232917)
+++ gcc/testsuite/gfortran.dg/block_end_error_1.f90	(Arbeitskopie)
@@ -6,5 +6,5 @@
    block
    end block named ! { dg-error "Syntax error in END BLOCK statement" }
    return
-endsubroutine
+endsubroutine ! { dg-error "Expecting END BLOCK statement" }
 ! { dg-prune-output "Unexpected end of file" }