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

[Punnoose, Elizebeth]

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