[Bug c++/106125] New: [c++2a] Segmentation fault in constexpr initialization of static variable

[mameluc at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106125

            Bug ID: 106125
           Summary: [c++2a] Segmentation fault in constexpr initialization
                    of static variable
           Product: gcc
           Version: 10.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mameluc at gmail dot com
  Target Milestone: ---

Created attachment 53217
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53217&action=edit
Preprocessed file (compressed)

The following code triggers a segfault. Tested with g++ 10.3.0, -O0 to -O3

/* starts here */
template<typename ... T>
struct DataStructure
{
};

template<size_t N>
struct StringLiteral 
{
    constexpr StringLiteral (const char (&str)[N]) 
    {
        std::copy_n(str, N, value); 
    }

    constexpr auto operator<=>(const StringLiteral&) const = default;
    constexpr bool operator==(const StringLiteral&) const  = default;
    static constexpr auto len = N; 
    char value[N];
};

////////////////////////////////////////////////////////////////////////

template <StringLiteral Name, typename T>
struct Item
{
    constexpr static auto item_name = Name;
    T data;
};

////////////////////////////////////////////////////////////////////////

template <StringLiteral Target, typename... Rest>
struct Test
{
    static constexpr auto eq = false;
};

template <StringLiteral Target, typename First, typename... Rest>
struct Test<Target, First, Rest...>
{
    static constexpr auto eq = (Target == First::item_name) || Test<Target,
Rest...>::eq;
};

////////////////////////////////////////////////////////////////////////

template<typename T, typename ... Rest>
struct DataStructure<T, Rest ...>
{
    constexpr DataStructure()
        : first()
        , rest()
    {
        // this line!
        static_assert(!Test<T::item_name, Rest...>::eq, "repeated id in data
structure");
    }

    T first;
    DataStructure<Rest ... > rest;
};

DataStructure<
    Item<"Ident::ZUM", int>, 
    Item<"Ident::FOO", float>,
    Item<"Ident::BAR", float>
> data;

/* ends here */

g++-10 -save-temps -std=c++2a test_segfault.cpp
test_segfault.cpp: In constructor ‘constexpr DataStructure<T, Rest
...>::DataStructure()’:
test_segfault.cpp:58:50: internal compiler error: Segmentation fault
   58 |         static_assert(!Test<T::item_name, Rest...>::eq, "repeated id in
data structure");
      |                                                  ^
0x7f3d44ebe08f ???
       
/build/glibc-SzIz7B/glibc-2.31/signal/../sysdeps/unix/sysv/linux/x86_64/sigaction.c:0
0x7f3d44e9f082 __libc_start_main
        ../csu/libc-start.c:308
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-10/README.Bugs> for instructions.
make: *** [Makefile:2: all] Error 1

//////////////////////////////////////////////////////////////////////////////////////
Compiler info:

Using built-in specs.
COLLECT_GCC=g++-10
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa:hsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
10.3.0-1ubuntu1~20.04' --with-bugurl=file:///usr/share/doc/gcc-10/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-10
--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 --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-10-S4I5Pr/gcc-10-10.3.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-10-S4I5Pr/gcc-10-10.3.0/debian/tmp-gcn/usr,hsa
--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-mutex
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.3.0 (Ubuntu 10.3.0-1ubuntu1~20.04)