[Bug c++/65202] New: [5.0 regression]ICE segfault with constexpr/noexcept

[lucdanton at free dot fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65202

            Bug ID: 65202
           Summary: [5.0 regression]ICE segfault with constexpr/noexcept
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lucdanton at free dot fr

Created attachment 34866
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34866&action=edit
Reduced testcase

Using:

$ g++-trunk --version
g++-trunk (GCC) 5.0.0 20150223 (experimental)

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I get the following trace:

$ g++-trunk -std=c++1y main.cpp
main.cpp: In instantiation of 'decltype (adl::adl_swap(l, r)) adl::swap(L&, R&)
[with L = adl::ns::foo<adl::ns::bar>; R = adl::ns::foo<adl::ns::bar>; decltype
(adl::adl_swap(l, r)) = void]':
main.cpp:22:19:   required from here
main.cpp:12:54:   in constexpr expansion of
'adl::adl_swap<adl::ns::foo<adl::ns::bar>, adl::ns::foo<adl::ns::bar>, {}>((* &
l), (* & r))'
main.cpp:12:6: internal compiler error: Segmentation fault
 auto swap(L &l, R &r) noexcept(noexcept(adl::adl_swap(l, r)))
      ^
0xa93f2f crash_signal
    ../../gcc/gcc/toplev.c:383
0x6f0cfa cxx_eval_constant_expression
    ../../gcc/gcc/cp/constexpr.c:2943
0x6f138a cxx_eval_constant_expression
    ../../gcc/gcc/cp/constexpr.c:3118
0x6f068b cxx_eval_call_expression
    ../../gcc/gcc/cp/constexpr.c:1392
0x6f0e44 cxx_eval_constant_expression
    ../../gcc/gcc/cp/constexpr.c:3022
0x6f3627 is_sub_constant_expr(tree_node*)
    ../../gcc/gcc/cp/constexpr.c:3604
0x69761d check_noexcept_r
    ../../gcc/gcc/cp/except.c:1178
0xc8c7c4 walk_tree_1(tree_node**, tree_node* (*)(tree_node**, int*, void*),
void*, hash_set<tree_node*, default_hashset_traits>*, tree_node*
(*)(tree_node**, int*, tree_node* (*)(tree_node**, int*, void*), void*,
hash_set<tree_node*, default_hashset_traits>*))
    ../../gcc/gcc/tree.c:11086
0xc8df58 walk_tree_without_duplicates_1(tree_node**, tree_node*
(*)(tree_node**, int*, void*), void*, tree_node* (*)(tree_node**, int*,
tree_node* (*)(tree_node**, int*, void*), void*, hash_set<tree_node*,
default_hashset_traits>*))
    ../../gcc/gcc/tree.c:11416
0x69732f expr_noexcept_p(tree_node*, int)
    ../../gcc/gcc/cp/except.c:1255
0x697492 finish_noexcept_expr(tree_node*, int)
    ../../gcc/gcc/cp/except.c:1240
0x60c308 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
    ../../gcc/gcc/cp/pt.c:14895
0x625e9d maybe_instantiate_noexcept(tree_node*)
    ../../gcc/gcc/cp/pt.c:20012
0x64104f mark_used(tree_node*, int)
    ../../gcc/gcc/cp/decl2.c:4941
0x5da459 build_over_call
    ../../gcc/gcc/cp/call.c:7489
0x5e3261 build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, bool, int)
    ../../gcc/gcc/cp/call.c:4104
0x6ac979 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
    ../../gcc/gcc/cp/semantics.c:2407
0x660689 cp_parser_postfix_expression
    ../../gcc/gcc/cp/parser.c:6368
0x66274a cp_parser_unary_expression
    ../../gcc/gcc/cp/parser.c:7438
0x6632e8 cp_parser_binary_expression
    ../../gcc/gcc/cp/parser.c:8173
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

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Instead, I would expect the compiler to complain due to e.g. the namespaces
left
unclosed. (The testcase has been mechanically reduced so is nonsensical.) This
is what happens with 4.8 and 4.9.