[Bug c++/103912] New: ICE in a consteval function in cp_gimplify_expr, at cp/cp-gimplify.c:557

[Bug c++/103912] New: ICE in a consteval function in cp_gimplify_expr, at cp/cp-gimplify.c:557

[0xd34df00d at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

            Bug ID: 103912
           Summary: ICE in a consteval function in cp_gimplify_expr, at
                    cp/cp-gimplify.c:557
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 0xd34df00d at gmail dot com
  Target Milestone: ---

This program:


#include <string_view>

namespace
{
    constexpr uint64_t CalcHash (std::string_view name)
    {
        return 0;
    }

    template<typename T>
    struct Command
    {
        const uint64_t Hash_;
        const T Cmd_;

        consteval Command (std::string_view name, T cmd)
        : Hash_ { CalcHash (name) }
        , Cmd_ { cmd }
        {
        }
    };

    template<typename T>
    consteval auto MakeHash (auto&&... commands)
    {
        const std::initializer_list<Command<T>> commandsList { commands... };
        for (auto i = commandsList.begin (); i != std::prev (commandsList.end
()); ++i)
            for (auto j = std::next (i); j != commandsList.end (); ++j)
                if (i->Hash_ == j->Hash_)
                    throw "duplicate hashes";

        return [=] (std::string_view str)
        {
            const auto strHash = CalcHash (str);
            T result {};
            ((commands.Hash_ == strHash && (result = commands.Cmd_)) || ...);
            return result;
        };
    }
}

struct Foo
{
    int foo1(int x) { return x * 1; }
};

int bar(std::string_view arg)
{
    constexpr auto hash = MakeHash<int (Foo::*) (int)> (Command { "foo1",
&Foo::foo1 });

    Foo f {};
    auto res = hash(arg);
    return (f.*res)(42);
}


compiled with -std=c++20 (as in g++ -std=c++20 foo.cpp -o foo.o) results in


foo.cpp: In function 'consteval auto {anonymous}::MakeHash(auto:11&& ...) [with
T = int (Foo::*)(int); auto:11 = {{anonymous}::Command<int (Foo::*)(int)>}]':
foo.cpp:27:17: internal compiler error: in cp_gimplify_expr, at
cp/cp-gimplify.c:557
   27 |                 for (auto i = commandsList.begin (); i != std::prev
(commandsList.end ()); ++i)
      |                 ^~~
0x164bc1d internal_error(char const*, ...)
        ???:0
0x604ee1 fancy_abort(char const*, int, char const*)
        ???:0
0xa7662b gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*),
int)
        ???:0
0xa77265 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*),
int)
        ???:0
0xa7734c gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*),
int)
        ???:0
0xa77265 gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*),
int)
        ???:0
0xa7734c gimplify_expr(tree_node**, gimple**, gimple**, bool (*)(tree_node*),
int)
        ???:0
0xa85bd4 gimplify_body(tree_node*, bool)
        ???:0
0xa8611e gimplify_function_tree(tree_node*)
        ???:0
0x8fd5ab cgraph_node::analyze()
        ???:0
0x903af3 symbol_table::finalize_compilation_unit()
        ???:0
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://bugs.gentoo.org/> for instructions.


This reproduces both with gcc 11.1.0 and 11.2.1:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/11.2.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-11.2.1_p20211127/work/gcc-11-20211127/configure
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/11.2.1
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/11.2.1
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/11.2.1/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/11.2.1/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include/g++-v11
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/11.2.1/python
--enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt
--disable-werror --with-system-zlib --enable-nls --without-included-gettext
--disable-libunwind-exceptions --enable-checking=release
--with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo
11.2.1_p20211127 p3' --disable-esp --enable-libstdcxx-time
--with-build-config=bootstrap-lto --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu --enable-multilib
--with-multilib-list=m32,m64 --disable-fixed-point --enable-targets=all
--enable-libgomp --disable-libssp --disable-libada --disable-cet
--disable-systemtap --disable-valgrind-annotations --disable-vtable-verify
--disable-libvtv --without-zstd --enable-lto --with-isl
--disable-isl-version-check --disable-default-pie --enable-default-ssp
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.2.1 20211127 (Gentoo 11.2.1_p20211127 p3)

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-01-05
             Status|UNCONFIRMED                 |NEW
            Summary|ICE in a consteval function |ICE in a consteval function
                   |in cp_gimplify_expr, at     |which returns a lambda
                   |cp/cp-gimplify.c:557        |which takes a "non-POD"
                   |                            |argument and the consteval
                   |                            |has other code
             Blocks|                            |54367
     Ever confirmed|0                           |1

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed reduced testcase:
struct f{f();};
consteval auto MakeHash ()
{
    if (1) ;
    return [] (f str) { };
}

void bar(f arg)
{
    auto hash = MakeHash ();
    hash(arg);
}


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54367
[Bug 54367] [meta-bug] lambda expressions

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |marxin at gcc dot gnu.org

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r10-4303-gf968ef9b8df2bc22, was rejected before the revision.

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
This happens because of:
              /* Preserve a functions function context node.  It will
                 later be needed to output debug info.  */
              if (tree fn = decl_function_context (decl))
                {
                  cgraph_node *origin_node = cgraph_node::get_create (fn);
                  enqueue_node (origin_node);
                }
in cgraphunit.c, operator() of the lambda is needed, so it is enqueued and the
above forces gimplification of the consteval function too, which is a big no
no, such functions shouldn't exist.

The big question is what do we want to do for debug info in these cases.

When using instead:
struct A {A (); };

constexpr auto
foo ()
{
  if (1)
    ;
  return [] (A x) { };
}

void
bar (A x)
{
  constinit static auto h = foo ();
  h (x);
}
ipa.c discovers that foo isn't reachable even when it is needed (as function
context of the lambda) and throws away the body and in the debug info just
emits DW_TAG_subprogram etc. for foo, but only emits non-code related stuff for
it.

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

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

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

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 52130
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52130&action=edit
gcc12-pr103912.patch

Untested fix.

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:54fa7daefe35cacf4a933947d1802318da193c01

commit r12-6423-g54fa7daefe35cacf4a933947d1802318da193c01
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Jan 10 20:49:11 2022 +0100

    c++: Ensure some more that immediate functions aren't gimplified [PR103912]

    Immediate functions should never be emitted into assembly, the FE doesn't
    genericize them and does various things to ensure they aren't gimplified.
    But the following testcase ICEs anyway due to that, because the consteval
    function returns a lambda, and operator() of the lambda has
    decl_function_context of the consteval function.  cgraphunit.c then
    does:
                  /* Preserve a functions function context node.  It will
                     later be needed to output debug info.  */
                  if (tree fn = decl_function_context (decl))
                    {
                      cgraph_node *origin_node = cgraph_node::get_create (fn);
                      enqueue_node (origin_node);
                    }
    which enqueues the immediate function and then tries to gimplify it,
    which results in ICE because it hasn't been genericized.

    When I try similar testcase with constexpr instead of consteval and
    static constinit auto instead of auto in main, what happens is that
    the functions are gimplified, later ipa.c discovers they aren't reachable
    and sets body_removed to true for them (and clears other flags) and we end
    up with a debug info which has the foo and bar functions without
    DW_AT_low_pc and other code specific attributes, just stuff from its BLOCK
    structure and in there the lambda with DW_AT_low_pc etc.

    The following patch attempts to emulate that behavior early, so that cgraph
    doesn't try to gimplify those and pretends they were already gimplified
    and found unused and optimized away.

    2022-01-10  Jakub Jelinek  <jakub@redhat.com>

            PR c++/103912
            * semantics.c (expand_or_defer_fn): For immediate functions, set
            node->body_removed to true and clear analyzed, definition and
            force_output.
            * decl2.c (c_parse_final_cleanups): Ignore immediate functions for
            expand_or_defer_fn.

            * g++.dg/cpp2a/consteval26.C: New test.

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:18abe529d092ca00903fe6a9ec5210c91d45030f

commit r11-9499-g18abe529d092ca00903fe6a9ec5210c91d45030f
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Jan 10 20:49:11 2022 +0100

    c++: Ensure some more that immediate functions aren't gimplified [PR103912]

    Immediate functions should never be emitted into assembly, the FE doesn't
    genericize them and does various things to ensure they aren't gimplified.
    But the following testcase ICEs anyway due to that, because the consteval
    function returns a lambda, and operator() of the lambda has
    decl_function_context of the consteval function.  cgraphunit.c then
    does:
                  /* Preserve a functions function context node.  It will
                     later be needed to output debug info.  */
                  if (tree fn = decl_function_context (decl))
                    {
                      cgraph_node *origin_node = cgraph_node::get_create (fn);
                      enqueue_node (origin_node);
                    }
    which enqueues the immediate function and then tries to gimplify it,
    which results in ICE because it hasn't been genericized.

    When I try similar testcase with constexpr instead of consteval and
    static constinit auto instead of auto in main, what happens is that
    the functions are gimplified, later ipa.c discovers they aren't reachable
    and sets body_removed to true for them (and clears other flags) and we end
    up with a debug info which has the foo and bar functions without
    DW_AT_low_pc and other code specific attributes, just stuff from its BLOCK
    structure and in there the lambda with DW_AT_low_pc etc.

    The following patch attempts to emulate that behavior early, so that cgraph
    doesn't try to gimplify those and pretends they were already gimplified
    and found unused and optimized away.

    2022-01-10  Jakub Jelinek  <jakub@redhat.com>

            PR c++/103912
            * semantics.c (expand_or_defer_fn): For immediate functions, set
            node->body_removed to true and clear analyzed, definition and
            force_output.
            * decl2.c (c_parse_final_cleanups): Ignore immediate functions for
            expand_or_defer_fn.

            * g++.dg/cpp2a/consteval26.C: New test.

    (cherry picked from commit 54fa7daefe35cacf4a933947d1802318da193c01)

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 11.3 too.

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lutztonineubert at gmail dot com

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
*** Bug 105060 has been marked as a duplicate of this bug. ***

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:9b80a9b0466f02e6e30790396c2b1545a9f8ff94

commit r10-10665-g9b80a9b0466f02e6e30790396c2b1545a9f8ff94
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Jan 10 20:49:11 2022 +0100

    c++: Ensure some more that immediate functions aren't gimplified [PR103912]

    Immediate functions should never be emitted into assembly, the FE doesn't
    genericize them and does various things to ensure they aren't gimplified.
    But the following testcase ICEs anyway due to that, because the consteval
    function returns a lambda, and operator() of the lambda has
    decl_function_context of the consteval function.  cgraphunit.c then
    does:
                  /* Preserve a functions function context node.  It will
                     later be needed to output debug info.  */
                  if (tree fn = decl_function_context (decl))
                    {
                      cgraph_node *origin_node = cgraph_node::get_create (fn);
                      enqueue_node (origin_node);
                    }
    which enqueues the immediate function and then tries to gimplify it,
    which results in ICE because it hasn't been genericized.

    When I try similar testcase with constexpr instead of consteval and
    static constinit auto instead of auto in main, what happens is that
    the functions are gimplified, later ipa.c discovers they aren't reachable
    and sets body_removed to true for them (and clears other flags) and we end
    up with a debug info which has the foo and bar functions without
    DW_AT_low_pc and other code specific attributes, just stuff from its BLOCK
    structure and in there the lambda with DW_AT_low_pc etc.

    The following patch attempts to emulate that behavior early, so that cgraph
    doesn't try to gimplify those and pretends they were already gimplified
    and found unused and optimized away.

    2022-01-10  Jakub Jelinek  <jakub@redhat.com>

            PR c++/103912
            * semantics.c (expand_or_defer_fn): For immediate functions, set
            node->body_removed to true and clear analyzed, definition and
            force_output.
            * decl2.c (c_parse_final_cleanups): Ignore immediate functions for
            expand_or_defer_fn.

            * g++.dg/cpp2a/consteval26.C: New test.

    (cherry picked from commit 54fa7daefe35cacf4a933947d1802318da193c01)

[Bug c++/103912] ICE in a consteval function which returns a lambda which takes a "non-POD" argument and the consteval has other code

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103912

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed for 10.4 too.