Fix casting in-memory values of primitive types to const reference
It's currently not possible to cast an in-memory value of a primitive
type to const reference:
```
(gdb) p Q.id
$1 = 42
(gdb) p (int&)Q.id
$2 = (int &) @0x22fd0c: 42
(gdb) p (const int&)Q.id
Attempt to take address of value not located in memory.
```
And if in a function call an argument needs the same kind of casting,
it also doesn't work:
```
(gdb) l f3
39 int f3(const int &i)
40 {
41 return i;
42 }
(gdb) p f3(Q.id)
Attempt to take address of value not located in memory.
```
It's because when the constness of the type changes in a call to
value_cast, a new not_lval value is allocated, which doesn't exist
in the target memory.
Fixed by ignoring const/volatile/restrict qualifications in
value_cast when comparing cast type to original type, so the new
value will point to the same location as the original value:
```
(gdb) p (int&)i
$2 = (int &) @0x39f72c: 1
(gdb) p (const int&)i
$3 = (const int &) @0x39f72c: 1
(gdb) p f3(Q.id)
$4 = 42
```
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=19423
Approved-By: Tom Tromey <tom@tromey.com>
diff --git a/gdb/testsuite/gdb.cp/casts.exp b/gdb/testsuite/gdb.cp/casts.exp
index ca82ab0..9f7638c 100644
--- a/gdb/testsuite/gdb.cp/casts.exp
+++ b/gdb/testsuite/gdb.cp/casts.exp
@@ -180,6 +180,9 @@
gdb_test "print (unsigned long long) (LeftRight *) (Right *) r_value == gd_value" \
" = true"
+gdb_test "print (const int &) gd.left" \
+ " = \\(const int \\&\\) @$nonzero_hex: 23"
+
gdb_test "print reinterpret_cast<LeftRight *>(l) == lr_l" " = true"
gdb_test "print reinterpret_cast<LeftRight *>(r) == lr_r" " = true"
gdb_test "print reinterpret_cast<Left *>(lr) == l_lr" " = true"
diff --git a/gdb/testsuite/gdb.cp/ref-params.cc b/gdb/testsuite/gdb.cp/ref-params.cc
index f038d71..3ef2868 100644
--- a/gdb/testsuite/gdb.cp/ref-params.cc
+++ b/gdb/testsuite/gdb.cp/ref-params.cc
@@ -36,6 +36,11 @@
return f1(C); /* Set breakpoint marker2 here. */
}
+int f3(const int &i)
+{
+ return i;
+}
+
struct OtherParent {
OtherParent (int other_id0) : other_id(other_id0) { }
int other_id;
@@ -64,6 +69,7 @@
f2(Q);
f2(QR);
+ f3(Q.id);
MultiChild MQ(53);
MultiChild& MQR = MQ;
diff --git a/gdb/testsuite/gdb.cp/ref-params.exp b/gdb/testsuite/gdb.cp/ref-params.exp
index 03bb8e6..e5c28e6 100644
--- a/gdb/testsuite/gdb.cp/ref-params.exp
+++ b/gdb/testsuite/gdb.cp/ref-params.exp
@@ -62,3 +62,4 @@
gdb_test "print f1(MQR)" ".* = 53"
gdb_test "print mf1(MQR)" ".* = 106"
gdb_test "print mf2(MQR)" ".* = 106"
+gdb_test "print f3(Q.id)" ".* = 42"
diff --git a/gdb/valops.c b/gdb/valops.c
index 1a943f0..52cce28 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -411,7 +411,8 @@ value_cast (struct type *type, struct value *arg2)
In this case we want to preserve the LVAL of ARG2 as this allows the
resulting value to be used in more places. We do this by calling
VALUE_COPY if appropriate. */
- if (types_deeply_equal (arg2->type (), type))
+ if (types_deeply_equal (make_unqualified_type (arg2->type ()),
+ make_unqualified_type (type)))
{
/* If the types are exactly equal then we can avoid creating a new
value completely. */
