https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119378
Bug ID: 119378
Summary: Nested template class friend of template class
produces "internal compiler error: unexpected
expression ‘T’ of kind template_parm_index"
Product: gcc
Version: 12.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: sebastian at radakovits dot se
Target Milestone: ---
Created attachment 60825
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=60825&action=edit
The program generating the error
GCC version: (Ubuntu 12.3.0-1ubuntu1~22.04) 12.3.0
Target: x86_64-linux-gnu
GCC Configured with:
../src/configure -v --with-pkgversion='Ubuntu 12.3.0-1ubuntu1~22.04' --with-
bugurl=file:///usr/share/doc/gcc-12/README.Bugs
--enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-12
--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-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-12-ALHxjy/gcc-12-12.3.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-12-ALHxjy/gcc-12-12.3.0/debian/tmp-gcn/usr
--enable-offload-defaulted --without-cuda-driver --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Command line: gcc-12 main.cpp
Output:
main.cpp: In instantiation of ‘class C<int>’:
main.cpp:16:12: required from here
main.cpp:8:9: internal compiler error: unexpected expression ‘T’ of kind
template_parm_index
8 | class C {
| ^
0x7f0291921d8f __libc_start_call_main
../sysdeps/nptl/libc_start_call_main.h:58
0x7f0291921e3f __libc_start_main_impl
../csu/libc-start.c:392
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-12/README.Bugs> for instructions.
----------
When testing in Compiler Explorer (https://godbolt.org/z/aWE1aqnee) it seems
that the bug is only present in versions of gcc >= 4.8.1 and main.cpp compiles
fine with gcc version 4.7.4 and earlier.
Compiling the program with clang only produces a warning:
main.cpp:11:24: warning: dependent nested name specifier 'A<T>::' for friend
template declaration is not supported; ignoring this friend declaration
[-Wunsupported-friend]
friend class A<T>::B;
~~~~~~^
----------
template <int T>
struct A {
template <typename Q>
class B {};
};
template <class R>
class C {
template <int T>
template <class Q>
friend class A<T>::B;
};
int main() {
C<void> ctg;
}
