[Bug c++/108936] New: internal compiler error: in type_has_nontrivial_copy_init, at cp/tree.cc:4525

[Bug c++/108936] New: internal compiler error: in type_has_nontrivial_copy_init, at cp/tree.cc:4525

[movaki1751 at vootin dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108936

            Bug ID: 108936
           Summary: internal compiler error: in
                    type_has_nontrivial_copy_init, at cp/tree.cc:4525
           Product: gcc
           Version: 12.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: movaki1751 at vootin dot com
  Target Milestone: ---

Created attachment 54538
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54538&action=edit
The attachment was generated with the "-freport-bug" option. It contains all
the required technical information and the preprocessed file

Trying to use "(union{short s;char c;}){1}.c != 1;" in a constexpr to determine
host byte order


Expected behavior:
error: accessing ‘<unnamed union>::c’ member instead of initialized ‘<unnamed
union>::s’ member in constant expression
    6 |     static constexpr bool BigEndianHost = (union{short s;char c;}){1}.c
!= 1;


Actual behavior:
internal compiler error: in type_has_nontrivial_copy_init, at cp/tree.cc:4525
     6 |     static constexpr bool BigEndianHost = (union{short s;char
c;}){1}.c != 1;


If i remove "template<bool BigEndianData = true>" from the example code (see
attachment), i get the expected behavior


The exact version of GCC, and other required information is in the attachment

[Bug c++/108936] internal compiler error: in type_has_nontrivial_copy_init, at cp/tree.cc:4525

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108936

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-02-27
                 CC|                            |jason at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Started likely with r9-1493-g8945521a50a7dd26, it was rejected before the
revision.

[Bug c++/108936] internal compiler error: in type_has_nontrivial_copy_init, at cp/tree.cc:4525

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108936

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
template<bool BigEndianData = true>
struct Endianness
{
  static constexpr bool BigEndianHost = (union{short s;char c;}){1}.c != 1;
};

int main()
{
  Endianness<>::BigEndianHost;
}


$ ./cc1plus -quiet bz.C
bz.C: In instantiation of ‘constexpr const bool Endianness<>::BigEndianHost’:
bz.C:9:17:   required from here
bz.C:4:69: internal compiler error: in type_has_nontrivial_copy_init, at
cp/tree.cc:4631
    4 |   static constexpr bool BigEndianHost = (union{short s;char c;}){1}.c
!= 1;
      |                                                                 ~~~~^
0x1058fa5 type_has_nontrivial_copy_init(tree_node const*)
        /home/mpolacek/src/gcc/gcc/cp/tree.cc:4631
0x1047c78 build_target_expr_with_type(tree_node*, tree_node*, int)
        /home/mpolacek/src/gcc/gcc/cp/tree.cc:904
0x1047e65 get_target_expr(tree_node*, int)
        /home/mpolacek/src/gcc/gcc/cp/tree.cc:948
0x10112be finish_compound_literal(tree_node*, tree_node*, int, fcl_t)
        /home/mpolacek/src/gcc/gcc/cp/semantics.cc:3356
0xfbfd62 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:21515
0xfb763b tsubst_non_call_postfix_expression
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:19866
0xfbe98a tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:21314
0xfbab12 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:20576
0xfb7019 tsubst_expr(tree_node*, tree_node*, int, tree_node*)
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:19775
0xfa50de tsubst_init
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:17014
0xfd413b regenerate_decl_from_template
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:26334
0xfd62e8 instantiate_body
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:26651
0xfd8412 instantiate_decl(tree_node*, bool, bool)
        /home/mpolacek/src/gcc/gcc/cp/pt.cc:27006
0xdc8886 mark_used(tree_node*, int)
        /home/mpolacek/src/gcc/gcc/cp/decl2.cc:5840
0x1016792 finish_id_expression_1
        /home/mpolacek/src/gcc/gcc/cp/semantics.cc:4252
0x1017079 finish_id_expression(tree_node*, tree_node*, tree_node*, cp_id_kind*,
bool, bool, bool*, bool, bool, bool, bool, char const**, unsigned int)
        /home/mpolacek/src/gcc/gcc/cp/semantics.cc:4398
0xed94b6 cp_parser_primary_expression
        /home/mpolacek/src/gcc/gcc/cp/parser.cc:6149
0xedd48c cp_parser_postfix_expression
        /home/mpolacek/src/gcc/gcc/cp/parser.cc:7777
0xee0e91 cp_parser_unary_expression
        /home/mpolacek/src/gcc/gcc/cp/parser.cc:9138
0xee243b cp_parser_cast_expression
        /home/mpolacek/src/gcc/gcc/cp/parser.cc:10044