[PATCH] [RFC] Fix ptype bug actually exercised in userdef.exp

Pedro Alves
2013-02-13T20:31:47Z

I happened to notice a bug with ptype &Ref, and found out userdef.exp
actually exercises the bug. With:

class Container
{
public:
Member m;

Member& operator* ();
};

Member& Container::operator* ()
{
return this->m;
}

And 'c' is of type Container:

(gdb) p c
$1 = {m = {z = -9192}}
(gdb) p *c
$2 = (Member &) @0x7fffffffda20: {z = -9192}
(gdb) ptype *c
type = class Member {
public:
int z;
} &

(gdb) p &*c
$3 = (Member *) 0x7fffffffda20

(gdb) ptype &*c
type = class Member {
public:
int z;
} &*
(gdb)

Notice that last print (&*c) on says the type is a pointer - that's
how you get the address behind a reference. But notice the last ptype
instead says the type of the same expression is a pointer _reference_.
This looks like a bug to me.

This patch fixes it. The issue is that we're entering the VALUE_LVAL
(x) == lval_memory branch by mistake for references. The fix is just
to swap the tests so references are checked first, like value_addr
also handles references first.

Comments?

Tested on x86_64 Fedora 17.

2013-02-13 Pedro Alves <palves@redhat.com>

* eval.c (evaluate_subexp_for_address) <default_case_after_eval,
EVAL_AVOID_SIDE_EFFECTS>: Swap and handle TYPE_CODE_REF before
lval_memory.

2013-02-13 Pedro Alves <palves@redhat.com>

* gdb.cp/userdef.exp (ptype &*c): Don't expect an &.
---
gdb/eval.c | 10 ++++------
gdb/testsuite/gdb.cp/userdef.exp | 2 +-
2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/gdb/eval.c b/gdb/eval.c
index f4b39cb..96efa21 100644
--- a/gdb/eval.c
+++ b/gdb/eval.c
@@ -2929,12 +2929,10 @@ evaluate_subexp_for_address (struct expression *exp, int *pos,
{
struct type *type = check_typedef (value_type (x));

- if (VALUE_LVAL (x) == lval_memory || value_must_coerce_to_target (x))
- return value_zero (lookup_pointer_type (value_type (x)),
- not_lval);
- else if (TYPE_CODE (type) == TYPE_CODE_REF)
- return value_zero (lookup_pointer_type (TYPE_TARGET_TYPE (type)),
- not_lval);
+ if (TYPE_CODE (type) == TYPE_CODE_REF)
+ return value_zero (lookup_pointer_type (TYPE_TARGET_TYPE (type)), not_lval);
+ else if (VALUE_LVAL (x) == lval_memory || value_must_coerce_to_target (x))
+ return value_zero (lookup_pointer_type (value_type (x)), not_lval);
else
error (_("Attempt to take address of "
"value not located in memory."));
diff --git a/gdb/testsuite/gdb.cp/userdef.exp b/gdb/testsuite/gdb.cp/userdef.exp
index 7c20b33..51a1bb5 100644
--- a/gdb/testsuite/gdb.cp/userdef.exp
+++ b/gdb/testsuite/gdb.cp/userdef.exp
@@ -133,7 +133,7 @@ gdb_test "break A2::operator +" ".*Breakpoint $decimal at.*"
gdb_test "print c" "\\\$\[0-9\]* = {m = {z = .*}}"
gdb_test "print *c" "\\\$\[0-9\]* = \\(Member &\\) @$hex: {z = .*}"
gdb_test "print &*c" "\\\$\[0-9\]* = \\(Member \\*\\) $hex"
-gdb_test "ptype &*c" "type = (struct|class) Member {(\[\r\n \]+public:)?\[\r\n \]+int z;\[\r\n\].*} &\\*"
+gdb_test "ptype &*c" "type = (struct|class) Member {(\[\r\n \]+public:)?\[\r\n \]+int z;\[\r\n\].*} \\*"

gdb_test "print operator== (mem1, mem2)" " = false"
gdb_test "print operator== (mem1, mem1)" " = true"