gdb: Forward VALUE_LVAL when avoiding side effects for STRUCTOP_PTR

Assume that we have a C program like this:

  struct foo_type
  {
    int var;
  } foo;

  struct foo_type *foo_ptr = &foo;

  int
  main ()
  {
    return foo_ptr->var;
  }

Then GDB should be able to evaluate the following, however, it currently
does not:

  (gdb) start
  ...
  (gdb) whatis &(foo_ptr->var)
  Attempt to take address of value not located in memory.

The problem is that in EVAL_AVOID_SIDE_EFFECTS mode,
eval.c:evaluate_subexp_standard always returns a not_lval value as the
result for a STRUCTOP_PTR operation. As a consequence, the rest of
the code believes that one cannot take the address of the returned
value.

This patch fixes STRUCTOP_PTR handling so that the VALUE_LVAL
attribute for the returned value is properly initialized.  After this
change, the above session becomes:

  (gdb) start
  ...
  (gdb) whatis &(foo_ptr->var)
  type = int *

This commit is largely the same as commit 2520f728b710 (Forward
VALUE_LVAL when avoiding side effects for STRUCTOP_STRUCT) but applied
to STRUCTOP_PTR rather than STRUCTOP_STRUCT.  Both of these commits are
building on top of commit ac1ca910d74d (Fixes for PR exp/15364).

gdb/ChangeLog:

	* eval.c (evaluate_subexp_standard): If EVAL_AVOID_SIDE_EFFECTS
	mode, forward the VALUE_LVAL attribute to the returned value in
	the STRUCTOP_PTR case.

gdb/testsuite/ChangeLog:

	* gdb.base/whatis.c: Extend the test case.
	* gdb.base/whatis.exp: Add additional tests.

1 files changed, 83 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/whatis.exp b/gdb/testsuite/gdb.base/whatis.exp
index 93a4d44..0cdcf5b 100644
--- a/gdb/testsuite/gdb.base/whatis.exp
+++ b/gdb/testsuite/gdb.base/whatis.exp
@@ -294,6 +294,47 @@ gdb_test "whatis v_struct2" \
     "type = struct \{\.\.\.\}" \
     "whatis unnamed structure"
 
+gdb_test "whatis &v_struct1" \
+    "type = struct t_struct \\*"
+
+gdb_test "whatis &v_struct2" \
+    "type = struct {\\.\\.\\.} \\*"
+
+gdb_test "whatis v_struct_ptr1" \
+    "type = struct t_struct \\*"
+
+gdb_test "whatis v_struct_ptr2" \
+    "type = struct {\\.\\.\\.} \\*"
+
+gdb_test "whatis &v_struct_ptr1" \
+    "type = struct t_struct \\*\\*"
+
+gdb_test "whatis &v_struct_ptr2" \
+    "type = struct {\\.\\.\\.} \\*\\*"
+
+gdb_test "whatis v_struct1.v_char_member" \
+    "type = char"
+
+gdb_test "whatis v_struct2.v_char_member" \
+    "type = char"
+
+gdb_test "whatis v_struct_ptr1->v_char_member" \
+    "type = char"
+
+gdb_test "whatis v_struct_ptr2->v_char_member" \
+    "type = char"
+
+gdb_test "whatis &(v_struct1.v_char_member)" \
+    "type = char \\*"
+
+gdb_test "whatis &(v_struct2.v_char_member)" \
+    "type = char \\*"
+
+gdb_test "whatis &(v_struct_ptr1->v_char_member)" \
+    "type = char \\*"
+
+gdb_test "whatis &(v_struct_ptr2->v_char_member)" \
+    "type = char \\*"
 
 # test whatis command with union types
 gdb_test "whatis v_union" \
@@ -308,6 +349,48 @@ gdb_test "whatis v_union2" \
     "type = union \{\.\.\.\}" \
     "whatis unnamed union"
 
+gdb_test "whatis &v_union" \
+    "type = union t_union \\*"
+
+gdb_test "whatis &v_union2" \
+    "type = union {\\.\\.\\.} \\*"
+
+gdb_test "whatis v_union_ptr" \
+    "type = union t_union \\*"
+
+gdb_test "whatis v_union_ptr2" \
+    "type = union {\\.\\.\\.} \\*"
+
+gdb_test "whatis &v_union_ptr" \
+    "type = union t_union \\*\\*"
+
+gdb_test "whatis &v_union_ptr2" \
+    "type = union {\\.\\.\\.} \\*\\*"
+
+gdb_test "whatis v_union.v_char_member" \
+    "type = char"
+
+gdb_test "whatis v_union2.v_char_member" \
+    "type = char"
+
+gdb_test "whatis v_union_ptr->v_char_member" \
+    "type = char"
+
+gdb_test "whatis v_union_ptr2->v_char_member" \
+    "type = char"
+
+gdb_test "whatis &(v_union.v_char_member)" \
+    "type = char \\*"
+
+gdb_test "whatis &(v_union2.v_char_member)" \
+    "type = char \\*"
+
+gdb_test "whatis &(v_union_ptr->v_char_member)" \
+    "type = char \\*"
+
+gdb_test "whatis &(v_union_ptr2->v_char_member)" \
+    "type = char \\*"
+
 
 # Using stabs we will mark these functions as prototyped.  This
 # is harmless but causes an extra VOID to be printed.