https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115429
Bug ID: 115429
Summary: requires clause wrongly accepts unqualified access to
inherited static members
Product: gcc
Version: 14.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: eratchias at gmail dot com
Target Milestone: ---
Created attachment 58402
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58402&action=edit
Preprocessed minimal example
If we have:
- a templated class `B` with a non-private data member constexpr static bool
`con`
- a templated class `A` that is derived from `B` such that it's base isn't
fully instantiated(It's template parameters depend on template parameters of
`A`)
Then simple requires clauses(not enclosed in parenthesis) will have unqualified
access to `con`.
This should normally result in a compile error as it does if unqualified `con`
is used anywhere else in class `A`. Additionally the access it provides doesn't
even work the same way as the correct way of accessing it with `A::con` as it
is assumed to not change between different instantiations of `A`.
Extended example:
#include <iostream>
template <bool x>
class B {
public:
constexpr static bool con = x;
};
template<bool x = true>
class A: public B<x> {
public:
// Option 1: Incorrectly accepted
bool c() requires con {
return true;
}
// Option 2: Correct behaviour
// Doesn't compile: con was not declared
// bool c() requires (con) {
// return true;
// }
};
int main() {
A<> a{};
std::cout << a.c() << std::endl; // 1
std::cout << a.con << std::endl; // 1
// Here the method is chosen based on B<true> not B<false>
A<false> aa{};
std::cout << aa.c() << std::endl; // 1
std::cout << aa.con << std::endl; // 0
}
output of gcc -v:
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/14.1.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure
--enable-languages=ada,c,c++,d,fortran,go,lto,m2,objc,obj-c++,rust
--enable-bootstrap --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib
--mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://gitlab.archlinux.org/archlinux/packaging/packages/gcc/-/issues
--with-build-config=bootstrap-lto --with-linker-hash-style=gnu
--with-system-zlib --enable-__cxa_atexit --enable-cet=auto
--enable-checking=release --enable-clocale=gnu --enable-default-pie
--enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object
--enable-libstdcxx-backtrace --enable-link-serialization=1
--enable-linker-build-id --enable-lto --enable-multilib --enable-plugin
--enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-werror
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.1.1 20240522 (GCC)
The file is compiled with:
g++ -std=c++20 example-no-iostream.cpp
Code compiles without any warnings/errors.
