[Bug c++/105797] New: Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[Bug c++/105797] New: Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[northon_patrick3 at yahoo dot ca]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105797

            Bug ID: 105797
           Summary: Internal compiler error: Segmentation fault (
                    fn_type_unification ->
                    satisfaction_cache::satisfaction_cache ->
                    iterative_hash_template_arg )
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: northon_patrick3 at yahoo dot ca
  Target Milestone: ---

Created attachment 53061
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53061&action=edit
Result from -freport-bug

The code:
```
#include <type_traits>
#include <concepts>

template <typename T_>
struct AStruct
{
        using value_type = T_;
};

template <typename T_>
constexpr auto fc1(AStruct<T_> v)
        requires std::integral<typename std::decay_t<decltype(v)>::value_type>
        //requires std::integral<T_>
        { return v; }

template <typename T1_, typename T2_>
constexpr auto fc2(AStruct<T1_> v1, AStruct<T2_> v2)
        requires std::integral<typename std::decay_t<decltype(v1)>::value_type>
        { return v1; }

void test(AStruct<int> v1, AStruct<int> v2)
        { fc2(v1, v2); }

void test2(AStruct<int> v)
        { fc1(v); }
```


The command line:

```
g++ -std=c++20 test.cpp
```


The error:

```
test.cpp: In substitution of ‘template<class T_> constexpr auto
fc1(AStruct<T_>) requires  integral<typename
std::decay<decltype(v)>::type::value_type> [with T_ = int]’:
test.cpp:25:7:   required from here
test.cpp:25:14: internal compiler error: Segmentation fault
   25 |         { fc1(v); }
      |           ~~~^~~
0x1ac4724 internal_error(char const*, ...)
        ???:0
0x7f1693 iterative_hash_template_arg(tree_node*, unsigned int)
        ???:0
0x6bf9da satisfaction_cache::satisfaction_cache(tree_node*, tree_node*,
sat_info)
        ???:0
0x81bbd4 fn_type_unification(tree_node*, tree_node*, tree_node*, tree_node*
const*, unsigned int, tree_node*, unification_kind_t, int, conversion**, bool,
bool)
        ???:0
0x69d051 build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, int)
        ???:0
0x836c31 finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
        ???:0
0x7eaa63 c_parse_file()
        ???:0
0x914adb c_common_parse_file()
        ???:0
```


It happens from GCC 11.1 and onward to GCC 13 at commit
271072ca259dd285e7723d9bf6da7295e4090dfa.

GCC is configured with:

```
configure --prefix=/opt/pat-gcc --libdir=/opt/pat-gcc/lib
--libexecdir=/opt/pat-gcc/lib --enable-languages=c,c++,lto --with-isl
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --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
gdc_include_dir=/opt/pat-gcc/include/dlang/gdc
```


If I comment out either one of test or test2 functions, it compiles. If I
change either one of the requires clause to use T_ or T1_ instead of decltype,
it compiles. If I change either one of fc1 or fc2 to use auto instead of a
template<> clause, it compiles. So it seem to crash at a very specific
condition.

[Bug c++/105797] [11/12/13 Regression] Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105797

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org,
                   |                            |ppalka at gcc dot gnu.org
           Priority|P3                          |P2
            Summary|Internal compiler error:    |[11/12/13 Regression]
                   |Segmentation fault (        |Internal compiler error:
                   |fn_type_unification ->      |Segmentation fault (
                   |satisfaction_cache::satisfa |fn_type_unification ->
                   |ction_cache ->              |satisfaction_cache::satisfa
                   |iterative_hash_template_arg |ction_cache ->
                   |)                           |iterative_hash_template_arg
                   |                            |)
   Target Milestone|---                         |11.4
           Keywords|                            |ice-on-valid-code
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2022-05-31

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Started with r11-4859-gd3fd75d8694800:

commit d3fd75d869480044213553000d2c9dc236a4f7af
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon Nov 9 18:16:48 2020 -0500

    c++: Consider only relevant template arguments in sat_hasher

[Bug c++/105797] [11/12/13 Regression] Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105797

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
// PR c++/105797

namespace std {
template <int __v> struct integral_constant {
  static constexpr int value = __v;
};
template <typename _Tp> struct decay { typedef _Tp type; };
template <typename _Tp> using decay_t = typename decay<_Tp>::type;
template <typename>
constexpr bool is_integral_v = integral_constant<true>::value;
template <typename _Tp>
concept integral = is_integral_v<_Tp>;
} // namespace std
template <typename> struct AStruct { using value_type = int; };
template <typename T_>
void fc1(AStruct<T_> v) requires
    std::integral<typename std::decay_t<decltype(v)>::value_type>;
template <typename T1_, typename T2_>
void fc2(AStruct<T1_> v1, T2_) requires
    std::integral<typename std::decay_t<decltype(v1)>::value_type>;
AStruct<int> test_v1, test2_v;
int test_v2;
void test() { fc2(test_v1, test_v2); }
void test2() { fc1(test2_v); }

[Bug c++/105797] [11/12/13 Regression] Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105797

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |ppalka at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug c++/105797] [11/12/13 Regression] Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105797

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:df4f95dbd4764ffc1e8270e5b3c0fd71b6724562

commit r13-980-gdf4f95dbd4764ffc1e8270e5b3c0fd71b6724562
Author: Patrick Palka <ppalka@redhat.com>
Date:   Fri Jun 3 09:08:41 2022 -0400

    c++: find_template_parameters and PARM_DECLs [PR105797]

    As explained in r11-4959-gde6f64f9556ae3, the atom cache assumes two
    equivalent expressions (according to cp_tree_equal) must use the same
    template parameters (according to find_template_parameters).  This
    assumption turned out to not hold for TARGET_EXPR, which was addressed
    by that commit.

    But this assumption apparently doesn't hold for PARM_DECL either:
    find_template_parameters walks its DECL_CONTEXT but cp_tree_equal by
    default doesn't consider DECL_CONTEXT unless comparing_specializations
    is set.  Thus in the first testcase below, the atomic constraints of #1
    and #2 are equivalent according to cp_tree_equal, but according to
    find_template_parameters the former uses T and the latter uses both T
    and U (surprisingly).

    We could fix this assumption violation by setting comparing_specializations
    in the atom_hasher, which would make cp_tree_equal return false for the
    two atoms, but that seems overly pessimistic here.  Ideally the atoms
    should continue being considered equivalent and we instead fix
    find_template_paremeters to return just T for #2's atom.

    To that end this patch makes for_each_template_parm_r stop walking the
    DECL_CONTEXT of a PARM_DECL.  This should be safe to do because
    tsubst_copy / tsubst_decl only substitutes the TREE_TYPE of a PARM_DECL
    and doesn't bother substituting the DECL_CONTEXT, thus the only relevant
    template parameters are those used in its type.  any_template_parm_r is
    currently responsible for walking its TREE_TYPE, but I suppose it now makes
    sense for for_each_template_parm_r to do so instead.

    In passing this patch also makes for_each_template_parm_r stop walking
    the DECL_CONTEXT of a VAR_/FUNCTION_DECL since doing so after walking
    DECL_TI_ARGS is redundant, I think.

    I experimented with not walking DECL_CONTEXT for CONST_DECL, but the
    second testcase below demonstrates it's necessary to walk it.

            PR c++/105797

    gcc/cp/ChangeLog:

            * pt.cc (for_each_template_parm_r) <case FUNCTION_DECL, VAR_DECL>:
            Don't walk DECL_CONTEXT.
            <case PARM_DECL>: Likewise.  Walk TREE_TYPE.
            <case CONST_DECL>: Simplify.
            (any_template_parm_r) <case PARM_DECL>: Don't walk TREE_TYPE.

    gcc/testsuite/ChangeLog:

            * g++.dg/cpp2a/concepts-decltype4.C: New test.
            * g++.dg/cpp2a/concepts-memfun3.C: New test.

[Bug c++/105797] [11/12 Regression] Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105797

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[11/12/13 Regression]       |[11/12 Regression] Internal
                   |Internal compiler error:    |compiler error:
                   |Segmentation fault (        |Segmentation fault (
                   |fn_type_unification ->      |fn_type_unification ->
                   |satisfaction_cache::satisfa |satisfaction_cache::satisfa
                   |ction_cache ->              |ction_cache ->
                   |iterative_hash_template_arg |iterative_hash_template_arg
                   |)                           |)

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Fixed on trunk so far.

[Bug c++/105797] [11/12 Regression] Internal compiler error: Segmentation fault ( fn_type_unification -> satisfaction_cache::satisfaction_cache -> iterative_hash_template_arg )

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105797

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.4                        |11.5

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 11.4 is being released, retargeting bugs to GCC 11.5.