https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98083
Bug ID: 98083
Summary: [11 regression] -Warray-bounds false positive with
virtual derivation
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
With gcc 11 (20201128), the following fragment gives a bogus warning
when compiled with -Wall -O2:
-- x.cc ---------------------------------------------------------
struct base1
{
virtual ~base1();
};
struct base2
{
virtual ~base2();
};
class base3 : public base2, public virtual base1 {};
class istream_tie :
public virtual base1,
public virtual base3
{
};
void foo()
{
istream_tie in;
}
-----------------------------------------------------------------
$ g++ -c -Wall -O2 x.cc
x.cc: In function ‘void foo()’:
x.cc:13:7: warning: array subscript ‘base3[0]’ is partly outside array bounds
of ‘istream_tie [1]’ [-Warray-bounds]
13 | class istream_tie :
| ^~~~~~~~~~~
x.cc:21:15: note: while referencing ‘in’
21 | istream_tie in;
| ^~
x.cc:11:7: warning: array subscript ‘base3[0]’ is partly outside array bounds
of ‘istream_tie [1]’ [-Warray-bounds]
11 | class base3 : public base2, public virtual base1 {};
| ^~~~~
x.cc:21:15: note: while referencing ‘in’
21 | istream_tie in;
| ^~
This looks particularly funny since the input source does not anywhere
use array indexing. But this appears to have something to do with the
use of virtual derivation.
