https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603
Bug ID: 104603
Summary: wrong detection of g++ -Warray-bounds about downcast
Product: gcc
Version: 10.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: herumi at nifty dot com
Target Milestone: ---
Created attachment 52477
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52477&action=edit
a minimal sample of the bug
g++-10.3.0 and g++-11.2 -O2 -Warray-bounds on Ubuntu 20.04.3 LTS show wrong
warnings to the attachment code.
g++ -O2 -Warray-bounds -DA t.cpp does not show the warnings.
g++-9 -O2 -Warray-bounds does not, too.
---
>cat t.cpp
struct Base {
bool isX_;
Base(bool isX = false) : isX_(isX) { }
bool isX() const { return isX_; }
bool operator==(const Base& rhs) const;
};
struct X : public Base {
X(const Base& b) : Base(true), b_(b) { }
bool operator==(const X& rhs) const { return b_ == rhs.b_; }
Base b_;
};
inline bool Base::operator==(const Base& rhs) const
{
return isX() && rhs.isX() && static_cast<const X&>(*this) ==
static_cast<const X&>(rhs);
}
Base base;
#ifndef A
void f()
{
X(base) == X(base);
}
#endif
int main()
{
#ifdef A
X(base) == X(base);
#endif
}
---
---
% g++-10 --version
g++-10 (Ubuntu 10.3.0-1ubuntu1~20.04) 10.3.0
% g++-10 -O2 -Warray-bounds array-bounds-bug.cpp
array-bounds-bug.cpp: In function 'void f()':
array-bounds-bug.cpp:18:29: warning: array subscript 2 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:9: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:18:29: warning: array subscript 2 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:20: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:18:29: warning: array subscript 3 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:9: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:18:29: warning: array subscript 3 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:20: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:18:29: warning: array subscript 4 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:9: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:18:29: warning: array subscript 4 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:20: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:18:29: warning: array subscript 5 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:9: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:18:29: warning: array subscript 5 is outside array bounds
of 'X [1]' [-Warray-bounds]
18 | bool isX() const { return isX_; }
| ^~~~
array-bounds-bug.cpp:38:20: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:24:51: warning: array subscript 2 is outside array bounds
of 'X [1]' [-Warray-bounds]
24 | bool operator==(const X& rhs) const { return b_ == rhs.b_; }
| ~~~^~~~~~~~~
array-bounds-bug.cpp:38:9: note: while referencing '<anonymous>'
38 | X(base) == X(base);
| ^
array-bounds-bug.cpp:24:58: warning: array subscript 2 is outside array bounds
of 'X [1]' [-Warray-bounds]
24 | bool operator==(const X& rhs) const { return b_ == rhs.b_; }
| ~~~~^~
array-bounds-bug.cpp:38:20: note: while referencing '<anonymous>'
38 | X(base) == X(base);
---
