https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109761
Bug ID: 109761
Summary: Nested class destructor's noexcept specification
incorrectly considered as too loose compared to the
outer class
Product: gcc
Version: 11.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: andysem at mail dot ru
Target Milestone: ---
Consider the following piece of code:
template< typename T >
T declval() noexcept;
struct base
{
virtual ~base() {}
};
class outer :
public base
{
protected:
class nested
{
private:
outer& m_outer;
public:
explicit nested(outer& o) noexcept(noexcept(o.on_nested_ctor())) :
m_outer(o)
{
o.on_nested_ctor();
}
nested(nested const&) = delete;
nested& operator= (nested const&) = delete;
~nested() noexcept(noexcept(declval<outer&>().on_nested_dtor()))
{
m_outer.on_nested_dtor();
}
};
public:
~outer() {}
protected:
void on_nested_ctor();
void on_nested_dtor();
};
This wrongly fails to compile:
$ g++ -std=gnu++17 -o nested_noexcept_dtor.o -c nested_noexcept_dtor.cpp
nested_noexcept_dtor.cpp:28:9: error: looser exception specification on
overriding virtual function ‘outer::nested::~nested() noexcept (false)’
28 | ~nested()
noexcept(noexcept(declval<outer&>().on_nested_dtor()))
| ^
nested_noexcept_dtor.cpp:6:13: note: overridden function is ‘virtual
base::~base() noexcept’
6 | virtual ~base() {}
| ^
The compiler tries to match the ~nested() noexcept specification against the
~base()'s as if nested was derived from base, but it is not. ~nested() noexcept
specification has no bearing on the outer class hierarchy.
$ g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
11.3.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-11
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-11-xKiWfi/gcc-11-11.3.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-xKiWfi/gcc-11-11.3.0/debian/tmp-gcn/usr
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04)
