https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87671
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The problem is that GDB sees a stack address for the int* member of the
unique_ptr, but it should be a pointer to the 'int' on the heap:
Breakpoint 1, A::A (this=0x7fffffffd2b7, ptr=std::unique_ptr<int> = {...}) at
up.cc:7
(gdb) p &ptr
$6 = (std::unique_ptr<int, std::default_delete<int> > *) 0x7fffffffd290
(gdb) p ptr._M_t._M_t._M_head_impl
$7 = (int *) 0x7fffffffd2b8
The Incorrect value for *ptr is just because it dereferences that bad address.
If you step into the operator* function you see that the right address is
returned from get()
(gdb) step
std::unique_ptr<int, std::default_delete<int> >::operator*
(this=0x7fffffffd2b8) at
/home/jwakely/gcc/8/include/c++/8.2.1/bits/unique_ptr.h:329
std::unique_ptr<int, std::default_delete<int> >::get (this=0x7fffffffd2b8) at
/home/jwakely/gcc/8/include/c++/8.2.1/bits/unique_ptr.h:343
(gdb) finish
Run till exit from #0 std::unique_ptr<int, std::default_delete<int> >::get
(this=0x7fffffffd2b8) at
/home/jwakely/gcc/8/include/c++/8.2.1/bits/unique_ptr.h:343
std::unique_ptr<int, std::default_delete<int> >::operator*
(this=0x7fffffffd2b8) at
/home/jwakely/gcc/8/include/c++/8.2.1/bits/unique_ptr.h:330
Value returned is $8 = (int *) 0x614e70
(gdb) p *$8
$9 = 42
I don't know why GDB sees a bad value for the unique_ptr's data member.
