re PR fortran/77505 (Negative character length not treated as LEN=0)

2016-12-01  Elizebeth Punnoose  <elizebeth.punnoose@hpe.com>

	PR fortran/77505
	* trans-array.c (trans_array_constructor): Treat negative character
	length as LEN = 0.


2016-12-01  Elizebeth Punnoose  <elizebeth.punnoose@hpe.com>

	PR fortran/77505
	* gfortran.dg/char_length_20.f90: New test.
	* gfortran.dg/char_length_21.f90: Ditto.

From-SVN: r243143

gcc/fortran/ChangeLog

+2016-12-01  Elizebeth Punnoose  <elizebeth.punnoose@hpe.com>
+
+	PR fortran/77505
+	* trans-array.c (trans_array_constructor): Treat negative character
+	length as LEN = 0.
+
 2016-12-01  Steven G. Kargl  <kargl@gcc.gnu.org>
 
 	PR fortran/78279

gcc/fortran/trans-array.c

@@ -2226,6 +2226,8 @@ trans_array_constructor (gfc_ss * ss, locus * where)
   gfc_ss_info *ss_info;
   gfc_expr *expr;
   gfc_ss *s;
+  tree neg_len;
+  char *msg;
 
   /* Save the old values for nested checking.  */
   old_first_len = first_len;
@@ -2271,6 +2273,29 @@ trans_array_constructor (gfc_ss * ss, locus * where)
 	  gfc_conv_expr_type (&length_se, expr->ts.u.cl->length,
 			      gfc_charlen_type_node);
 	  ss_info->string_length = length_se.expr;
+
+	  /* Check if the character length is negative.  If it is, then
+	     set LEN = 0.  */
+	  neg_len = fold_build2_loc (input_location, LT_EXPR,
+				     boolean_type_node, ss_info->string_length,
+				     build_int_cst (gfc_charlen_type_node, 0));
+	  /* Print a warning if bounds checking is enabled.  */
+	  if (gfc_option.rtcheck & GFC_RTCHECK_BOUNDS)
+	    {
+	      msg = xasprintf ("Negative character length treated as LEN = 0");
+	      gfc_trans_runtime_check (false, true, neg_len, &length_se.pre,
+				       where, msg);
+	      free (msg);
+	    }
+
+	  ss_info->string_length
+	    = fold_build3_loc (input_location, COND_EXPR,
+			       gfc_charlen_type_node, neg_len,
+			       build_int_cst (gfc_charlen_type_node, 0),
+			       ss_info->string_length);
+	  ss_info->string_length = gfc_evaluate_now (ss_info->string_length,
+						     &length_se.pre);
+
 	  gfc_add_block_to_block (&outer_loop->pre, &length_se.pre);
 	  gfc_add_block_to_block (&outer_loop->post, &length_se.post);
 	}

gcc/testsuite/ChangeLog

+2016-12-01  Elizebeth Punnoose  <elizebeth.punnoose@hpe.com>
+
+	PR fortran/77505
+	* gfortran.dg/char_length_20.f90: New test.
+	* gfortran.dg/char_length_21.f90: Ditto.
+
 2016-12-01  Steven G. Kargl  <kargl@gcc.gnu.org>
 
 	PR fortran/78279

gcc/testsuite/gfortran.dg/char_length_20.f90

+! { dg-do run }
+! { dg-options "-fcheck=bounds" }
+program rabbithole
+   implicit none
+   character(len=:), allocatable :: text_block(:)
+   integer i, ii
+   character(len=10) :: cten='abcdefghij'
+   character(len=20) :: ctwenty='abcdefghijabcdefghij'
+   ii = -6
+   text_block=[ character(len=ii) :: cten, ctwenty ]
+   if (any(len_trim(text_block) /= 0)) call abort
+end program rabbithole
+! { dg-output "At line 10 of file .*char_length_20.f90.*Fortran runtime warning: Negative character length treated as LEN = 0" }

gcc/testsuite/gfortran.dg/char_length_21.f90

+! { dg-do run }
+program rabbithole
+   implicit none
+   character(len=:), allocatable :: text_block(:)
+   integer i, ii
+   character(len=10) :: cten='abcdefghij'
+   character(len=20) :: ctwenty='abcdefghijabcdefghij'
+   ii = -6
+   text_block = [character(len=ii) :: cten, ctwenty]
+   if (any(len_trim(text_block) /= 0)) call abort
+end program rabbithole