binutils-gdb/gdb/testsuite/gdb.cp/casts.cc
Hannes Domani 23cdd9431a Fix reinterpret_cast for classes with multiple inheritance
Currently a reinterpret_cast may change the pointer value if
multiple inheritance is involved:
```
(gdb) p r
$1 = (Right *) 0x22f75c
(gdb) p reinterpret_cast<LeftRight*>(r)
$2 = (LeftRight *) 0x22f758
```

It's because value_cast is called in this case, which automatically
does up- and downcasting.

Fixed by simply using the target pointer type in a copy of the
original value:
```
(gdb) p r
$1 = (Right *) 0x3bf87c
(gdb) p reinterpret_cast<LeftRight*>(r)
$2 = (LeftRight *) 0x3bf87c
```

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18861
Approved-By: Tom Tromey <tom@tromey.com>
2024-03-20 18:02:06 +01:00

105 lines
1.5 KiB
C++

#include <cstdint>
struct A
{
int a;
A (int aa): a (aa) {}
};
struct B: public A
{
int b;
B (int aa, int bb): A (aa), b(bb) {}
};
struct Alpha
{
virtual void x() { }
};
struct Gamma
{
};
struct Derived : public Alpha
{
};
struct VirtuallyDerived : public virtual Alpha
{
};
struct DoublyDerived : public VirtuallyDerived,
public virtual Alpha,
public Gamma
{
};
struct Left
{
int left;
};
struct Right
{
int right;
};
struct LeftRight : public Left, public Right
{
};
struct VirtualLeft
{
virtual ~VirtualLeft () {}
int left;
};
struct VirtualRight
{
virtual ~VirtualRight () {}
int right;
};
struct VirtualLeftRight : public VirtualLeft, public VirtualRight
{
};
int
main (int argc, char **argv)
{
A *a = new B(42, 1729);
B *b = (B *) a;
A &ar = *b;
B &br = (B&)ar;
Derived derived;
DoublyDerived doublyderived;
Alpha *ad = &derived;
Alpha *add = &doublyderived;
LeftRight gd;
gd.left = 23;
gd.right = 27;
unsigned long long gd_value = (unsigned long long) (std::uintptr_t)&gd;
unsigned long long r_value = (unsigned long long) (Right *) &gd;
LeftRight *lr = &gd;
Left *l = lr;
Right *r = lr;
LeftRight *lr_l = reinterpret_cast<LeftRight *>(l);
LeftRight *lr_r = reinterpret_cast<LeftRight *>(r);
Left *l_lr = reinterpret_cast<Left *>(lr);
Right *r_lr = reinterpret_cast<Right *>(lr);
VirtualLeftRight *vlr = new VirtualLeftRight ();
VirtualLeft *vl = vlr;
VirtualRight *vr = vlr;
return 0; /* breakpoint spot: casts.exp: 1 */
}