[Bug c++/126699] New: invalid constexpr causes internal compiler error: in build_data_member_initialization, at cp/constexpr.cc:462

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126699

            Bug ID: 126699
           Summary: invalid constexpr causes internal compiler error: in
                    build_data_member_initialization, at
                    cp/constexpr.cc:462
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lu.maltsis at postgrad dot manchester.ac.uk
  Target Milestone: ---

<source>: In constructor 'constexpr base<<anonymous> >::base(int)':
<source>:9:11: warning: division by zero [-Wdiv-by-zero]
    9 |   { y = 1 / 0; }
      |         ~~^~~
<source>: In function 'int main()':
<source>:21:26:   in 'constexpr' expansion of '((foo*)(& bar1))->foo::foo(1,
2)'
   21 |   constexpr foo bar1{1, 2};
      |                          ^
<source>:16:38:   in 'constexpr' expansion of '((foo*)this)->foo::foo(a)'
   16 |   constexpr foo(int a, int b) : foo{a}{}
      |                                      ^
<source>:15:35: error: 'constexpr base<<anonymous> >::base(int) [with int
<anonymous> = 2]' called in a constant expression
   15 |   constexpr foo(int a) : base<2>{a}{}
      |                                   ^
<source>:8:13: note: 'constexpr base<<anonymous> >::base(int) [with int
<anonymous> = 2]' is not usable as a 'constexpr' function because:
    8 |   constexpr base(int a) : base{}
      |             ^~~~
<source>:8:13: internal compiler error: in build_data_member_initialization, at
cp/constexpr.cc:462
0x2b8ff08 diagnostics::context::diagnostic_impl(rich_location*,
diagnostics::metadata const*, diagnostics::option_id, char const*,
__va_list_tag (*) [1], diagnostics::kind)
        ???:0
0x2b84b4b internal_error(char const*, ...)
        ???:0
0xb3f80c fancy_abort(char const*, int, char const*)
        ???:0
0xbc5f6a explain_invalid_constexpr_fn(tree_node*)
        ???:0
0xbad5d1 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad752 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad448 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad9fd cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad188 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad5d1 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad752 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad448 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad188 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xbad5d1 cxx_eval_constant_expression(constexpr_ctx const*, tree_node*,
value_cat, bool*, bool*, tree_node**)
        ???:0
0xea58ee store_init_value(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0xc51616 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int,
cp_decomp*)
        ???:0
0xd94eb3 c_parse_file()
        ???:0
0xf28289 c_common_parse_file()
        ???:0
/cefs/71/7162170c670fadfdb1a6fa5f_gcc-trunk-20260806/bin/../libexec/gcc/x86_64-linux-gnu/17.0.0/cc1plus
-quiet -imultiarch x86_64-linux-gnu -iprefix
/cefs/71/7162170c670fadfdb1a6fa5f_gcc-trunk-20260806/bin/../lib/gcc/x86_64-linux-gnu/17.0.0/
-D_GNU_SOURCE <source> -quiet -dumpdir /app/ -dumpbase output.cpp -dumpbase-ext
.cpp -masm=intel -mtune=generic -march=x86-64 -g -fdiagnostics-color=always
-fno-verbose-asm -o /app/output.s
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
Compiler returned: 1

Code:

template<int>
struct base
{
  int y{};

  base() = default;

  constexpr base(int a) : base{}
  { y = 1 / 0; }
};

struct foo : base<1>, base<2>
{
  int x{};
  constexpr foo(int a) : base<2>{a}{}
  constexpr foo(int a, int b) : foo{a}{}
};

int main()
{
  constexpr foo bar1{1, 2};
}


https://godbolt.org/z/6YEKj6zba

Commit Hash: 56d98177f592e0cf8b3118c4859b416658e0be3a