[Bug c++/95772] New: warning desired when default operator= cannot be constructued
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95772
Bug ID: 95772
Summary: warning desired when default operator= cannot be
constructued
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: marcpawl at gmail dot com
Target Milestone: ---
https://godbolt.org/z/eXckPe
#include
class Const {
public:
int const i_;
Const(int i) : i_(i) {}
Const& operator=(Const& rhs) = default;
};
int main(int argc, char**) {
Const c{argc};
static_assert(!std::is_assignable::value,
"should not be able to assign i_");
#ifdef ASSIGN
Const d{argc + 1};
d = c;
#endif
return c.i_;
}
I expected a diagnostic saying that operator= cannot be defaulted which is seen
if the ASSIGN code is enabled. The code compiles cleanly.
When I wrote this bug in a large code base with -03 and -flto the code will
fail with illegal instructions and other memory corruption errors. No problem
without optimization.
[Bug c++/95772] warning desired when default operator= cannot be constructued
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95772 --- Comment #2 from Marc Pawlowsky --- I understand that it is deleted, but if somebody says it should be defaulted when it is defaulted that is most likely an error, and it would be nice if a warning were generated.
[Bug c++/95772] warning desired when default operator= cannot be constructued
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95772 Marc Pawlowsky changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED Resolution|--- |INVALID --- Comment #4 from Marc Pawlowsky --- "Do the default thing" vs "generate the default". What would your feeling be for a clang-tidy rule under readability? It was a surprise to me, especially since I never have actually read the spec since C++98, just training articles/videos and quick scans through the odd committee paper.
[Bug c++/92735] New: unused member variable causes code to compile for member to function for undefined function
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92735
Bug ID: 92735
Summary: unused member variable causes code to compile for
member to function for undefined function
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: marcpawl at gmail dot com
Target Milestone: ---
Marc Pawlowsky
Thu, Nov 28, 8:25 PM (23 hours ago)
to gcc-bugzilla-account-request
https://godbolt.org/z/SFZmZJ
In clang you get
no member names 'hello' in 'Bad'
which is the expected result.
In all GCC versions using --std=c++17 from 5.2 onwards the code compiles.
#include
#include
struct Foo {
virtual void hello(int) = 0;
};
struct Bar : public Foo {
void hello(int) override {};
};
struct Bad { };
template
struct is_Foo {
using hello_fn_t = void (T::*)(int);
constexpr static void (T::*hello)(int) = &T::hello;
static constexpr bool value=true;
};
template
auto say(T& t) -> std::enable_if_t::value, void>{
//U u; // Line 22
//t.hello(4); // Line 23
puts("hello\n");
}
int main()
{
//Bar b;;
//Foo& f = b;
//say(b);
//say(f);
Bad bad;
say(bad);
}
If you change say to
template >
void say(T& t)
{
U u; // Line 22
//t.hello(4); // Line 23
}
you get the same errors in clang, but no errors in gcc.
==
on a related not I sent to clang bug report where if value is not static the
code will compile.
[Bug c++/92735] unused member variable causes code to compile for member to function for undefined function
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92735
--- Comment #4 from Marc Pawlowsky ---
(In reply to Jonathan Wakely from comment #2)
> For the case reported here, Clang and EDG do reject it, but I'm not yet
> convinced GCC is wrong to accept it.
>
> The implicit instantiation of is_Foo causes:
>
> "the implicit instantiation of the declarations, but not of the definitions,
> of the non-deleted class member functions, member classes, scoped member
> enumerations, static data members, member templates, and friends;"
>
> and:
>
> "in particular, the initialization (and any associated side effects) of a
> static data member does not occur unless the static data member is itself
> used in a way that requires the definition of the static data member to
> exist."
>
> Nothing requires the instantiation of is_Foo::hello.
FYI, Forcing the use of hello does cause a compile time error.
template
struct is_Foo {
using hello_fn_t = void (T::*)(int);
constexpr static void (T::*hello)(int) = &T::hello;
static constexpr bool value=(!!hello);
};
source>:16:46: error: 'hello' is not a member of 'Bad'
16 | constexpr static void (T::*hello)(int) = &T::hello;
[Bug c++/92852] New: location references block not in block tree
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92852
Bug ID: 92852
Summary: location references block not in block tree
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: marcpawl at gmail dot com
Target Milestone: ---
https://godbolt.org/z/Kh3xWR
Add...
#include
#include
#include
void foo()
{
std::ostream& message_stream = std::cout;
auto data = std::make_tuple(3,4.5,"cd");
auto format = [&message_stream](auto && x) { message_stream << x ;};
std::apply([&](auto const& ...x){(..., format(x));}, data);
}
x86-64 gcc (trunk) (Editor #1, Compiler #2) C++
x86-64 gcc (trunk)
-O0 -std=c++17
1
x86-64 gcc (trunk) - 2085ms
#2 with x86-64 gcc (trunk)
: In lambda function:
:12:2: error: location references block not in block tree
12 | }
| ^
&cout
std::basic_ostream::operator<< (&cout, _1);
during IPA pass: *free_lang_data
:12:2: internal compiler error: verify_gimple failed
Please submit a full bug report,
with preprocessed source if appropriate.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1
[Bug c++/115580] New: decltype of nullptr error with -Werror=nonnull
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115580
Bug ID: 115580
Summary: decltype of nullptr error with -Werror=nonnull
Product: gcc
Version: 14.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: marcpawl at gmail dot com
Target Milestone: ---
-Werror=nonnull returns error when using nullptr to get type of member
function.
Even though we are using -Werror=nonnull, there should be no diagnostic
since the function is never evaluated, and it is non-virtual.
https://godbolt.org/z/3oh1199Wh
https://stackoverflow.com/questions/5580253/how-do-i-get-the-return-type-of-a-member-function-without-an-object
class WithMember {
public:
int foo();
};
decltype(((WithMember*)nullptr)->foo()) footype;
:7:37: error: 'this' pointer is null [-Werror=nonnull]
7 | decltype(((WithMember*)nullptr)->foo()) footype;
| ~~~^~
:4:7: note: in a call to non-static member function 'int
WithMember::foo()'
4 | int foo();
| ^~~
:7:37: error: 'this' pointer is null [-Werror=nonnull]
7 | decltype(((WithMember*)nullptr)->foo()) footype;
| ~~~^~
:4:7: note: in a call to non-static member function 'int
WithMember::foo()'
4 | int foo();
| ^~~
cc1plus: some warnings being treated as errors
Compiler returned: 1
