[Bug c++/100723] New: [8/9/10/11] ICE in tsubst when using std::variant in templated class using CTAD

[Bug c++/100723] New: [8/9/10/11] ICE in tsubst when using std::variant in templated class using CTAD

[cadet.gabriel at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100723

            Bug ID: 100723
           Summary: [8/9/10/11] ICE in tsubst when using std::variant in
                    templated class using CTAD
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cadet.gabriel at gmail dot com
  Target Milestone: ---

The following code compile in others compiler, but fails to compile on every
version of g++ I've checked (8 to 12). As per bug reporting guidelines, I've
added .ii file as an attachment.

In this example, this code occured inside a noexcept specifier, but it also
happened when writting a template classe to check if all types inside a
std::variant respect some constexpr predicate.

Strangely enough, if I use some static constexpr, the bug does not occurs.

--------------------------------------------
#include <iostream>
#include <type_traits>
#include <variant>
#include <vector>
#include <unordered_map>
#include <string>

#define TEMPLATE_DECL_SUB \
    template <typename, typename, typename...> class Map, \
    class Other

#define TEMPLATE_DECL \
    template <TEMPLATE_DECL_SUB>

template <TEMPLATE_DECL class Value, TEMPLATE_DECL_SUB>
struct trait_impl {
    using value_t = Value<Map, Other>;
    using object_t = Map<Other, value_t>;
    using other_t = Other;
    using variant_t = std::variant<other_t, object_t *>;

    trait_impl(value_t const &) {}
};

template <typename T>
using trait = decltype(trait_impl{std::declval<T>()});

TEMPLATE_DECL
struct test_type {
    using trait_t = trait<test_type>;
    using other_t = typename trait<test_type>::other_t;
    using variant_t = typename trait_t::variant_t;
    other_t _val;

    static constexpr bool noex = std::is_nothrow_constructible_v<other_t,
Other>;

    //test_type() noexcept(noex): _val() {} // Works fine with this line
instead of the next.
    test_type() noexcept(std::is_nothrow_constructible_v<other_t, Other>):
_val() {}
    test_type(test_type const& oth) : _val(oth._val) {}
};

int main(void)
{
    test_type<std::unordered_map, int> t;
    return 0;
}
------------------------------------------

I first found this bug in archlinux g++ packages, then used docker +
self-compiled g++ to check whether it was only in the current arch version or
in other as well. 
Here is g++12 output (I recompiled it to have some debug infos and confirm the
bug still exist.) :

------------------------------------------

Using built-in specs.
COLLECT_GCC=/home/phantomas/sources/gcc_from_source/build/out/bin/g++
COLLECT_LTO_WRAPPER=/home/phantomas/sources/gcc_from_source/build/out/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure
--prefix=/home/phantomas/sources/gcc_from_source/build/out
--with-linker-hash-style=gnu --with-system-zlib --enable-languages=c,c++
--enable-__cxa_atexit --enable-cet=auto --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id
--enable-lto --enable-multilib --enable-plugin --enable-shared
--enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-libunwind-exceptions --disable-werror
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20210518 (experimental) (GCC) 
COLLECT_GCC_OPTIONS='-std=c++17' '-g3' '-Wall' '-Wextra' '-v' '-save-temps'
'-shared-libgcc' '-mtune=generic' '-march=x86-64' '-dumpdir' 'a-'

/home/phantomas/sources/gcc_from_source/build/out/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/cc1plus
-E -quiet -v -dD -D_GNU_SOURCE tsubst_bug.cpp -mtune=generic -march=x86-64
-std=c++17 -Wall -Wextra -g3 -fworking-directory -fpch-preprocess -o
a-tsubst_bug.ii
ignoring nonexistent directory
"/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/x86_64-pc-linux-gnu

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/backward

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/include
 /usr/local/include
 /home/phantomas/sources/gcc_from_source/build/out/include

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/include-fixed
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-std=c++17' '-g3' '-Wall' '-Wextra' '-v' '-save-temps'
'-shared-libgcc' '-mtune=generic' '-march=x86-64' '-dumpdir' 'a-'

/home/phantomas/sources/gcc_from_source/build/out/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/cc1plus
-fpreprocessed a-tsubst_bug.ii -quiet -dumpdir a- -dumpbase tsubst_bug.cpp
-dumpbase-ext .cpp -mtune=generic -march=x86-64 -g3 -Wall -Wextra -std=c++17
-version -o a-tsubst_bug.s
GNU C++17 (GCC) version 12.0.0 20210518 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 12.0.0 20210518 (experimental), GMP version
6.2.1, MPFR version 4.1.0, MPC version 1.2.1, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU C++17 (GCC) version 12.0.0 20210518 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 12.0.0 20210518 (experimental), GMP version
6.2.1, MPFR version 4.1.0, MPC version 1.2.1, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: f0735d336a82ba6e425f24ae91b2e265
tsubst_bug.cpp: In instantiation of ‘test_type<Map, Other>::test_type() [with
Map = std::unordered_map; Other = int]’:
tsubst_bug.cpp:44:40:   required from here
tsubst_bug.cpp:38:31: internal compiler error: in tsubst, at cp/pt.c:15652
   38 |     test_type() noexcept(std::is_nothrow_constructible_v<other_t,
Other>): _val() {}
      |                         
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
0x6ad098 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:15652
0xaa1fb4 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:20685
0xabd5f7 tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:16193
0xabd50b tsubst(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:16086
0xabfe6d tsubst_template_args(tree_node*, tree_node*, int, tree_node*)
        ../../gcc/gcc/cp/pt.c:13421
0xaa2ef6 tsubst_copy_and_build(tree_node*, tree_node*, int, tree_node*, bool,
bool)
        ../../gcc/gcc/cp/pt.c:19627
0xaa60b6 maybe_instantiate_noexcept(tree_node*, int)
        ../../gcc/gcc/cp/pt.c:25706
0xaa5ca3 maybe_instantiate_noexcept(tree_node*, int)
        ../../gcc/gcc/cp/pt.c:25649
0x99866a mark_used(tree_node*, int)
        ../../gcc/gcc/cp/decl2.c:5626
0x8e0c43 build_over_call
        ../../gcc/gcc/cp/call.c:9490
0x8de9f8 build_new_method_call_1
        ../../gcc/gcc/cp/call.c:10776
0x8e3891 build_new_method_call(tree_node*, tree_node*, vec<tree_node*, va_gc,
vl_embed>**, tree_node*, int, tree_node**, int)
        ../../gcc/gcc/cp/call.c:10852
0x8e3891 build_special_member_call(tree_node*, tree_node*, vec<tree_node*,
va_gc, vl_embed>**, tree_node*, int, int)
        ../../gcc/gcc/cp/call.c:10252
0x9b711c expand_default_init
        ../../gcc/gcc/cp/init.c:1992
0x9b711c expand_aggr_init_1
        ../../gcc/gcc/cp/init.c:2107
0x9b98f6 build_aggr_init(tree_node*, tree_node*, int, int)
        ../../gcc/gcc/cp/init.c:1841
0x963e7c build_aggr_init_full_exprs
        ../../gcc/gcc/cp/decl.c:6899
0x963e7c check_initializer
        ../../gcc/gcc/cp/decl.c:7060
0x989701 cp_finish_decl(tree_node*, tree_node*, bool, tree_node*, int)
        ../../gcc/gcc/cp/decl.c:8054
0xa74967 cp_parser_init_declarator
        ../../gcc/gcc/cp/parser.c:21915
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

---------------------------------------------

If I remove the unordered_map, a parsing error seems to occurs, I'll add it
here too to be thorough.
Here is the code:

---------------------------------------------

#include <iostream>
#include <type_traits>
#include <variant>
#include <vector>
#include <unordered_map>
#include <string>

#define TEMPLATE_DECL_SUB \
    /*template <typename, typename, typename...> class Map, \*/ \
    class Other

#define TEMPLATE_DECL \
    template <TEMPLATE_DECL_SUB>

template <TEMPLATE_DECL class Value, TEMPLATE_DECL_SUB>
struct trait_impl {
    using value_t = Value</*Map, */ Other>;
    //using object_t = Map<Other, value_t>;
    using other_t = Other;
    using variant_t = std::variant<other_t /*, object_t * */>;

    trait_impl(value_t const &) {}
};

template <typename T>
using trait = decltype(trait_impl{std::declval<T>()});

TEMPLATE_DECL
struct test_type {
    using trait_t = trait<test_type>;
    using other_t = typename trait<test_type>::other_t;
    using variant_t = typename trait_t::variant_t;
    other_t _val;

    static constexpr bool noex = std::is_nothrow_constructible_v<other_t,
Other>;

    //test_type() noexcept(noex): _val() {} // Works fine with this line
instead of the next.
    test_type() noexcept(std::is_nothrow_constructible_v<other_t, Other>):
_val() {}
    test_type(test_type const& oth) : _val(oth._val) {}
};

int main(void)
{
    test_type</* std::unordered_map, */ int> t;
    return 0;
}

-----------------------------------------------

And g++ output:

-----------------------------------------------

Using built-in specs.
COLLECT_GCC=/home/phantomas/sources/gcc_from_source/build/out/bin/g++
COLLECT_LTO_WRAPPER=/home/phantomas/sources/gcc_from_source/build/out/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure
--prefix=/home/phantomas/sources/gcc_from_source/build/out
--with-linker-hash-style=gnu --with-system-zlib --enable-languages=c,c++
--enable-__cxa_atexit --enable-cet=auto --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id
--enable-lto --enable-multilib --enable-plugin --enable-shared
--enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-libunwind-exceptions --disable-werror
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20210518 (experimental) (GCC) 
COLLECT_GCC_OPTIONS='-std=c++17' '-g3' '-Wall' '-Wextra' '-v' '-save-temps'
'-shared-libgcc' '-mtune=generic' '-march=x86-64' '-dumpdir' 'a-'

/home/phantomas/sources/gcc_from_source/build/out/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/cc1plus
-E -quiet -v -dD -D_GNU_SOURCE parse_bug.cpp -mtune=generic -march=x86-64
-std=c++17 -Wall -Wextra -g3 -fworking-directory -fpch-preprocess -o
a-parse_bug.ii
ignoring nonexistent directory
"/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/x86_64-pc-linux-gnu

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/../../../../include/c++/12.0.0/backward

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/include
 /usr/local/include
 /home/phantomas/sources/gcc_from_source/build/out/include

/home/phantomas/sources/gcc_from_source/build/out/lib/gcc/x86_64-pc-linux-gnu/12.0.0/include-fixed
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-std=c++17' '-g3' '-Wall' '-Wextra' '-v' '-save-temps'
'-shared-libgcc' '-mtune=generic' '-march=x86-64' '-dumpdir' 'a-'

/home/phantomas/sources/gcc_from_source/build/out/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/cc1plus
-fpreprocessed a-parse_bug.ii -quiet -dumpdir a- -dumpbase parse_bug.cpp
-dumpbase-ext .cpp -mtune=generic -march=x86-64 -g3 -Wall -Wextra -std=c++17
-version -o a-parse_bug.s
GNU C++17 (GCC) version 12.0.0 20210518 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 12.0.0 20210518 (experimental), GMP version
6.2.1, MPFR version 4.1.0, MPC version 1.2.1, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU C++17 (GCC) version 12.0.0 20210518 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 12.0.0 20210518 (experimental), GMP version
6.2.1, MPFR version 4.1.0, MPC version 1.2.1, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: f0735d336a82ba6e425f24ae91b2e265
parse_bug.cpp: In instantiation of ‘test_type<Other>::test_type() [with Other =
int]’:
parse_bug.cpp:44:21:   required from here
parse_bug.cpp:38:31: error: cannot convert ‘test_type<int>’ to ‘int’ in
initialization
   38 |     test_type() noexcept(std::is_nothrow_constructible_v<other_t,
Other>): _val() {}
      |                         
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Bug c++/100723] [8/9/10/11] ICE in tsubst when using std::variant in templated class using CTAD

[cadet.gabriel at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100723

--- Comment #1 from Gabriel Cadet <cadet.gabriel at gmail dot com> ---
Created attachment 50855
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50855&action=edit
Intermediate file, when compiling code that triggers the ICE.

The attachment wouldn't be sent, as it was too big ... Here it is, gzip
compressed so I it's accepted

[Bug c++/100723] [9/10/11] ICE in tsubst when using std::variant in templated class using CTAD

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100723

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[8/9/10/11] ICE in tsubst   |[9/10/11] ICE in tsubst
                   |when using std::variant in  |when using std::variant in
                   |templated class using CTAD  |templated class using CTAD
   Target Milestone|---                         |9.4
           Keywords|                            |ice-on-valid-code,
                   |                            |rejects-valid

[Bug c++/100723] [9/10/11/12] ICE in tsubst when using std::variant in templated class using CTAD

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100723

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|9.4                         |9.5

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 9.4 is being released, retargeting bugs to GCC 9.5.

[Bug c++/100723] [9/10/11/12] ICE in tsubst when using std::variant in templated class using CTAD

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100723

Patrick Palka <ppalka at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE
                 CC|                            |ppalka at gcc dot gnu.org

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
This also looks like a dup of 91911

*** This bug has been marked as a duplicate of bug 91911 ***