substring boundardy check (PR27588): writing a dg tests case

[Tobias Burnus]

Hello,

I have two questions:

a) Are there any pre-review comments to the following patch? It
currently writes such error messages:
Fortran runtime error: Substring out of bounds: lower bound less than
one (in file 'string2.f90', at line 5)
Fortran runtime error: Substring out of bounds: upper bound exceeds
string length (in file 'cbnd1.for', at line 5)
Is it ok like that?

b) I would like to add a test case to the test suit, but how does one
test for run-time errors?

If I have a solution for (b), I will submit a proper patch.

(With this patch, gfortran detects cbnd1, cbnd2 and cbnd4 of
http://www.polyhedron.com/pb05/linux/diagnose.html; cbnd3 can only be
detected when cross analysing in the file [e.g. "-gen-interface" in
Intel] or passing a specially crafted argument ["-C call" in NAG f95].)

Tobias


Index: gcc/fortran/trans-expr.c
===================================================================
*** gcc/fortran/trans-expr.c    (revision 117391)
--- gcc/fortran/trans-expr.c    (working copy)
*************** gfc_conv_substring (gfc_se * se, gfc_ref
*** 239,246 ****
--- 239,249 ----
    tree tmp;
    tree type;
    tree var;
+   tree fault;
    gfc_se start;
    gfc_se end;
+   locus loc;
+   char *msg;

    type = gfc_get_character_type (kind, ref->u.ss.length);
    type = build_pointer_type (type);
*************** gfc_conv_substring (gfc_se * se, gfc_ref
*** 272,277 ****
--- 275,292 ----
        gfc_conv_expr_type (&end, ref->u.ss.end, gfc_charlen_type_node);
        gfc_add_block_to_block (&se->pre, &end.pre);
      }
+   if (flag_bounds_check) {
+      gfc_get_backend_locus(&loc);
+      fault = fold_build2 (LT_EXPR, boolean_type_node, start.expr,
build_int_cst (gfc_charlen_type_node, 1));
+      asprintf (&msg, "Substring out of bounds: lower bound less than
one");
+      gfc_trans_runtime_check (fault, msg, &se->pre, &loc);
+
+      /* Check upper bound.  */
+      fault = fold_build2 (GT_EXPR, boolean_type_node, end.expr,
se->string_length);
+      asprintf (&msg, "Substring out of bounds: upper bound exceeds
string length");
+      gfc_trans_runtime_check (fault, msg, &se->pre, &loc);
+   }
+
    tmp = fold_build2 (MINUS_EXPR, gfc_charlen_type_node,
                     build_int_cst (gfc_charlen_type_node, 1),
                     start.expr);