[Bug fortran/77505] Negative character length not treated as LEN=0

[jb at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77505

Janne Blomqvist <jb at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jb at gcc dot gnu.org

--- Comment #8 from Janne Blomqvist <jb at gcc dot gnu.org> ---
(In reply to Elizebeth Punnoose from comment #6)
> Modified code with the warning message moved behind -fcheck=bounds.
> 
> Index: trans-array.c
> ===================================================================
> --- trans-array.c	(revision 241960)
> +++ trans-array.c	(working copy)
> @@ -2226,6 +2226,8 @@
>    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 +2273,27 @@
>  	  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, gfc_index_zero_node, 
> +				   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);
>  	}


Shouldn't you have build_int_cst (gfc_charlen_type_node, 0) instead of
gfc_index_zero_node?