vla: enable sizeof operator to work with variable length arrays

In C99 the sizeof operator computes the size of a variable length array
at runtime (6.5.3.4 The sizeof operator). This patch reflects the semantic
change in the debugger.

We now are able to get the size of a vla:

1| void foo (size_t n) {
2|   int vla[n];
3| }

(gdb) p sizeof(vla)

yields N * sizeof(int).

	* eval.c (evaluate_subexp_for_sizeof) <OP_VAR_VALUE>: If the type
	passed to sizeof is dynamic evaluate the argument to compute the length.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5f9450981aa2c4ebfe8844e8230a8e556be9bc05..ebeb2ef3a58185c218dc55127f6f99f20d88f1b6 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2014-04-11  Sanimir Agovic  <sanimir.agovic@intel.com>
+
+       * eval.c (evaluate_subexp_for_sizeof) <OP_VAR_VALUE>: If the type
+       passed to sizeof is dynamic evaluate the argument to compute the length.
+
 2014-04-11  Sanimir Agovic  <sanimir.agovic@intel.com>
 
        * dwarf2loc.c (dwarf2_locexpr_baton_eval): New function.

diff --git a/gdb/eval.c b/gdb/eval.c
index 36615e17cde24bfa1c713c6a37b2c706c26f6533..26454f60a2aca2ca9b81156a3571e96701a63fc8 100644 (file)
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -3040,8 +3040,14 @@ evaluate_subexp_for_sizeof (struct expression *exp, int *pos)
       return value_from_longest (size_type, (LONGEST) TYPE_LENGTH (type));
 
     case OP_VAR_VALUE:
-      (*pos) += 4;
       type = check_typedef (SYMBOL_TYPE (exp->elts[pc + 2].symbol));
+      if (is_dynamic_type (type))
+       {
+         val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_NORMAL);
+         type = value_type (val);
+       }
+      else
+       (*pos) += 4;
       return
        value_from_longest (size_type, (LONGEST) TYPE_LENGTH (type));