[PATCH] PR fortran/77505 -- Treat negative character length as LEN=0

[Punnoose, Elizebeth]

Please excuse the messy formatting in my initial mail. Resending with proper formatting.

This patch checks for negative character length in the array constructor, and treats it as LEN=0. 

A warning message is also printed if bounds checking is enabled.

Bootstrapped and regression tested the patch on x86_64-linux-gnu and aarch64-linux-gnu.

Index: ChangeLog
===================================================================
--- ChangeLog	(revision 242906)
+++ ChangeLog	(working copy)
@@ -1,3 +1,9 @@
+2016-11-30  Elizebeth Punnoose <elizebeth.punnoose@hpe.com>
+
+	PR fortran/77505
+	* trans-array.c (trans_array_constructor): Treat negative character
+	length as LEN=0.
+
 2016-11-27  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/78474

Index: trans-array.c
===================================================================
--- trans-array.c	(revision 242906)
+++ trans-array.c	(working copy)
@@ -2226,6 +2226,8 @@ trans_array_constructor (gfc_ss * ss, lo
   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 +2273,28 @@ trans_array_constructor (gfc_ss * ss, lo
 	  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 so consider it as 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 will be 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);
 	}


Index: ChangeLog
===================================================================
--- ChangeLog	(revision 242906)
+++ ChangeLog	(working copy)
@@ -1,3 +1,9 @@
+2016-11-30 Elizebeth Punnoose <elizebeth.punnoose@hpe.com>
+
+	PR fortran/77505
+	* gfortran.dg/pr77505_1.f90: New test.
+	* gfortran.dg/pr77505_2.f90: New test.
+
 2016-11-27  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/78474


Index: pr77505_1.f90
===================================================================
--- pr77505_1.f90             (nonexistent)
+++ pr77505_1.f90          (working copy)
@@ -0,0 +1,13 @@
+! { dg-do run }
+program rabbithole
+implicit none
+character(len=:),allocatable    :: text_block(:) integer                         
+:: i integer                         :: ii
+character(len=10)               :: cten='abcdefghij'
+character(len=20)               :: ctwenty='abcdefghijabcdefghij'
+ii=-6
+text_block=[ character(len=ii) :: cten, ctwenty ] write(*,*)'WRITE IT'
+write(*,'(a)')(trim(text_block(i)),i=1,size(text_block))
+end program rabbithole


Index: pr77505_2.f90
===================================================================
--- pr77505_2.f90             (nonexistent)
+++ pr77505_2.f90          (working copy)
@@ -0,0 +1,14 @@
+! { dg-options "-fcheck=bounds" }
+! { dg-do run }
+program rabbithole
+implicit none
+character(len=:),allocatable    :: text_block(:)
+integer                         :: i
+integer                         :: ii
+character(len=10)               :: cten='abcdefghij'
+character(len=20)               :: ctwenty='abcdefghijabcdefghij'
+ii=-6
+text_block=[ character(len=ii) :: cten, ctwenty ]
+write(*,*)'WRITE IT'
+write(*,'(a)')(trim(text_block(i)),i=1,size(text_block))
+end program rabbithole


Thanks,
Elizebeth