vla: evaluate operand of sizeof if its type is a vla

The c99 standard in "6.5.3.4 The sizeof operator" states:

 If the type of the operand is a variable length array type, the operand
 is evaluated;[...]

This patch mirrors the following c99 semantic in gdb:

 1| int vla[n][m];
 2| int i = 1;
 3| sizeof(vla[i++][0]); // No sideffect
 4| assert (i == 1);
 5| sizeof(vla[i++]);    // With sideffect
 6| assert (i == 2);

Note: ptype/whatis still do not allow any sideeffects.

This patch was motivated by:

  https://sourceware.org/ml/gdb-patches/2014-01/msg00732.html

gdb/ChangeLog:

	* eval.c (evaluate_subexp_for_sizeof): Add enum noside argument.
	(evaluate_subexp_standard): Pass noside argument.
	(evaluate_subexp_for_sizeof) <BINOP_SUBSCRIPT>: Handle subscript case
	if noside equals EVAL_NORMAL. If the subscript yields a vla type
	re-evaluate subscript operation with EVAL_NORMAL to enable sideffects.
	* gdbtypes.c (resolve_dynamic_bounds): Mark bound as evaluated.
	* gdbtypes.h (enum range_flags): Add RANGE_EVALUATED case.

testsuite/ChangeLog:

	* gdb.base/vla-sideeffect.c: New file.
	* gdb.base/vla-sideeffect.exp: New file.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2014-04-14  Sanimir Agovic  <sanimir.agovic@intel.com>
+
+	* eval.c (evaluate_subexp_for_sizeof): Add enum noside argument.
+	(evaluate_subexp_standard): Pass noside argument.
+	(evaluate_subexp_for_sizeof) <BINOP_SUBSCRIPT>: Handle subscript case
+	if noside equals EVAL_NORMAL. If the subscript yields a vla type
+	re-evaluate subscript operation with EVAL_NORMAL to enable sideffects.
+	* gdbtypes.c (resolve_dynamic_bounds): Mark bound as evaluated.
+	* gdbtypes.h (enum range_flags): Add RANGE_EVALUATED case.
+
 2014-04-14  Sanimir Agovic  <sanimir.agovic@intel.com>
 
 	* findvar.c (default_read_var_value): Resolve dynamic bounds if location

gdb/eval.c

@@ -50,7 +50,8 @@ extern int overload_resolution;
 
 /* Prototypes for local functions.  */
 
-static struct value *evaluate_subexp_for_sizeof (struct expression *, int *);
+static struct value *evaluate_subexp_for_sizeof (struct expression *, int *,
+						 enum noside);
 
 static struct value *evaluate_subexp_for_address (struct expression *,
 						  int *, enum noside);
@@ -2562,7 +2563,7 @@ evaluate_subexp_standard (struct type *expect_type,
 	  evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
 	  goto nosideret;
 	}
-      return evaluate_subexp_for_sizeof (exp, pos);
+      return evaluate_subexp_for_sizeof (exp, pos, noside);
 
     case UNOP_CAST:
       (*pos) += 2;
@@ -2996,10 +2997,13 @@ evaluate_subexp_with_coercion (struct expression *exp,
 
 /* Evaluate a subexpression of EXP, at index *POS,
    and return a value for the size of that subexpression.
-   Advance *POS over the subexpression.  */
+   Advance *POS over the subexpression.  If NOSIDE is EVAL_NORMAL
+   we allow side-effects on the operand if its type is a variable
+   length array.   */
 
 static struct value *
-evaluate_subexp_for_sizeof (struct expression *exp, int *pos)
+evaluate_subexp_for_sizeof (struct expression *exp, int *pos,
+			    enum noside noside)
 {
   /* FIXME: This should be size_t.  */
   struct type *size_type = builtin_type (exp->gdbarch)->builtin_int;
@@ -3052,6 +3056,37 @@ evaluate_subexp_for_sizeof (struct expression *exp, int *pos)
 	(*pos) += 4;
       break;
 
+      /* Deal with the special case if NOSIDE is EVAL_NORMAL and the resulting
+	 type of the subscript is a variable length array type. In this case we
+	 must re-evaluate the right hand side of the subcription to allow
+	 side-effects. */
+    case BINOP_SUBSCRIPT:
+      if (noside == EVAL_NORMAL)
+	{
+	  int pc = (*pos) + 1;
+
+	  val = evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_AVOID_SIDE_EFFECTS);
+	  type = check_typedef (value_type (val));
+	  if (TYPE_CODE (type) == TYPE_CODE_ARRAY)
+	    {
+	      type = check_typedef (TYPE_TARGET_TYPE (type));
+	      if (TYPE_CODE (type) == TYPE_CODE_ARRAY)
+		{
+		  type = TYPE_INDEX_TYPE (type);
+		  /* Only re-evaluate the right hand side if the resulting type
+		     is a variable length type.  */
+		  if (TYPE_RANGE_DATA (type)->flag_bound_evaluated)
+		    {
+		      val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_NORMAL);
+		      return value_from_longest
+			(size_type, (LONGEST) TYPE_LENGTH (value_type (val)));
+		    }
+		}
+	    }
+	}
+
+      /* Fall through.  */
+
     default:
       val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
       type = value_type (val);

gdb/gdbtypes.c

@@ -1719,6 +1719,7 @@ resolve_dynamic_bounds (struct type *type, CORE_ADDR addr)
   range_type = create_range_type (NULL,
 				  TYPE_TARGET_TYPE (range_type),
 				  &low_bound, &high_bound);
+  TYPE_RANGE_DATA (range_type)->flag_bound_evaluated = 1;
   return create_array_type (copy_type (type),
 			    elt_type,
 			    range_type);

gdb/gdbtypes.h

@@ -668,6 +668,11 @@ struct main_type
 	 subrange. This affects how the final hight bound is computed.  */
 
       int flag_upper_bound_is_count : 1;
+
+      /* True if LOW or/and HIGH are resolved into a static bound from
+	 a dynamic one.  */
+
+      int flag_bound_evaluated : 1;
     } *bounds;
 
   } flds_bnds;

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2014-04-14  Sanimir Agovic  <sanimir.agovic@intel.com>
+
+	* gdb.base/vla-sideeffect.c: New file.
+	* gdb.base/vla-sideeffect.exp: New file.
+
 2014-04-14  David Blaikie <dblaikie@gmail.com>
 
 	* gdb.mi/non-stop.c: Add return value for non-void function return

gdb/testsuite/gdb.base/vla-sideeffect.c

@@ -0,0 +1,42 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2014 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stddef.h>
+#define SIZE 10
+
+int
+main (void)
+{
+  int n = SIZE;
+  int i = 0;
+  int j = 0;
+  int vla2[SIZE][n];
+  int vla1[n];
+
+  for (i = 0; i < n; i++)
+    vla1[i] = (i * 2) + n;
+
+  for (i = 0; i < SIZE; i++)
+    for (j = 0; j < n; j++)
+      vla2[i][j] = (i + j) + n;
+
+
+  i = 0;
+  j = 0;
+
+  return 0;           /* vla-filled */
+}

gdb/testsuite/gdb.base/vla-sideeffect.exp

@@ -0,0 +1,89 @@
+# Copyright 2014 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Tests side-effects of sizeof evaluation.
+# Based on gcc/testsuite/gcc.dg/vla-4.c; vla-15.c
+
+standard_testfile
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_breakpoint [gdb_get_line_number "vla-filled"]
+gdb_continue_to_breakpoint "vla-filled"
+
+# Check side effects for sizeof argument.
+set sizeof_int [get_sizeof "int" 4]
+set sizeof_vla [ expr "10" * "$sizeof_int" ]
+
+gdb_test "print sizeof (vla1\[i++\])" " = ${sizeof_int}" \
+         "print sizeof (vla1\[i++\])"
+gdb_test "print i" " = 0" \
+         "print i - sizeof no side effects"
+
+gdb_test "print sizeof (++vla1\[0\])" " = ${sizeof_int}" \
+         "print sizeof (++vla1\[0\])"
+gdb_test "print vla1\[0\]" " = 10" \
+         "print vla1\[0\] - sizeof no side effects"
+
+gdb_test "ptype ++vla1\[0\]" "type = int" "ptype ++vla1\[0\]"
+gdb_test "print vla1\[0\]" " = 10" \
+         "print vla1\[0\] - ptype no side effects"
+
+gdb_test "whatis ++vla1\[0\]" "type = int" "whatis ++vla1\[0\]"
+gdb_test "print vla1\[0\]" " = 10" \
+         "print vla1\[0\] - whatis no side effects"
+
+
+gdb_test "print sizeof (vla2\[i++\])" " = ${sizeof_vla}" \
+         "print sizeof (vla2\[i++\])"
+gdb_test "print i" " = 1" \
+         "print i - sizeof with side effects (1)"
+
+gdb_test "print sizeof (vla2\[i++ + sizeof(j++)\])" " = ${sizeof_vla}" \
+         "print sizeof (vla2\[i++ + sizeof(j++)\])"
+gdb_test "print i" " = 2" \
+         "print i - sizeof with side effects (2)"
+gdb_test "print j" " = 0" \
+         "print j - sizeof with no side effects"
+
+gdb_test "ptype vla2\[i++\]" "type = int \\\[10\\\]" \
+         "ptype vla2\[i++\]"
+gdb_test "print i" " = 2" \
+         "print i - ptype with side effects (1)"
+
+gdb_test "ptype vla2\[i++ + sizeof(j++)\]" "type = int \\\[10\\\]" \
+         "ptype vla2\[i++ + sizeof(j++)\]"
+gdb_test "print i" " = 2" \
+         "print i - ptype with side effects (2)"
+gdb_test "print j" " = 0" \
+         "print j - ptype with no side effects"
+
+gdb_test "whatis vla2\[i++\]" "type = int \\\[10\\\]" \
+         "whatis vla2\[i++\]"
+gdb_test "print i" " = 2" \
+         "print i - whatis with side effects (1)"
+
+gdb_test "whatis vla2\[i++ + sizeof(j++)\]" "type = int \\\[10\\\]" \
+         "whatis vla2\[i++ + sizeof(j++)\]"
+gdb_test "print i" " = 2" \
+         "print i - whatis with side effects (2)"
+gdb_test "print j" " = 0" \
+         "print j - whatis with no side effects"