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[BUG]: void value not ignored as it ought to be #4117

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consolexinhun opened this issue Aug 4, 2022 · 3 comments · Fixed by #4275
Closed
2 of 3 tasks

[BUG]: void value not ignored as it ought to be #4117

consolexinhun opened this issue Aug 4, 2022 · 3 comments · Fixed by #4275
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bug regression Regression in a recent release

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@consolexinhun
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consolexinhun commented Aug 4, 2022 •
edited by henryiii
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Required prerequisites

Problem description

the bind code like this :

#include <pybind11/pybind11.h>
#include <iostream>
namespace py = pybind11;
using std::cout;
using std::endl;
class Animal {
public:
    virtual ~Animal() { }
    virtual void* go() = 0;
};

class PyAnimal : public Animal {
public:
    /* Inherit the constructors */
    using Animal::Animal;
    /* Trampoline (need one for each virtual function) */
    void* go() override {
        PYBIND11_OVERRIDE_PURE(
            void*, /* Return type */
            Animal,      /* Parent class */
            go,          /* Name of function in C++ (must match Python name) */
        );
    }
};

PYBIND11_MODULE(example, m) {
    py::class_<Animal, PyAnimal /* <--- trampoline*/>(m, "Animal")
        .def(py::init<>())
        .def("go", &Animal::go);
}

use pybind11 2.10.0,get error below:

example.cpp: In member function ‘virtual void* PyAnimal::go(int)’:
example.cpp:21:9: error: void value not ignored as it ought to be
   21 |         PYBIND11_OVERRIDE_PURE(
      |         ^~~~~~~~~~~~~~~~~~~~~~
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

but use pybind 2.9.2 is ok ，how to deal with it ？？

Reproducible example code

No response
@consolexinhun consolexinhun added the triage New bug, unverified label Aug 4, 2022
@henryiii henryiii added the regression Regression in a recent release label Aug 8, 2022
@henryiii henryiii mentioned this issue Aug 8, 2022
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@wassimj wassimj mentioned this issue Aug 11, 2022
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@jfehre jfehre mentioned this issue Sep 15, 2022
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@henryiii
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I get

tmp.cpp:18:9: error: cannot initialize return object of type 'void *' with an rvalue of type 'enable_if_t<std::is_same<void, intrinsic_t<void *>>::value, void>' (aka 'void')
        PYBIND11_OVERRIDE_PURE(
        ^~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2826:5: note: expanded from macro 'PYBIND11_OVERRIDE_PURE'
    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2788:9: note: expanded from macro 'PYBIND11_OVERRIDE_PURE_NAME'
        PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2754:20: note: expanded from macro 'PYBIND11_OVERRIDE_IMPL'
            return pybind11::detail::cast_safe<ret_type>(std::move(o));                           \
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

@henryiii
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Using #4272 and git bisect, the bad commit was 088ad4f, in #3861, by @laramiel.

@henryiii
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henryiii commented Oct 22, 2022 •
edited
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Debug mechanism:

$ gh pr checkout 279
$ cmd_to_run=c++ $(python3 -m pybind11 --file=example.cpp)
$ git bisect start
$ git bisect good v2.9.2
$ git bisect bad v2.10.0
$ git bisect run $cmd_to_run
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
Bisecting: 60 revisions left to test after this (roughly 6 steps)
[03252067db057777db75c2e5bcf0e69013b919ec] chore(deps): bump actions/upload-artifact from 2 to 3 (#3899)
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
example.cpp:18:9: error: cannot initialize return object of type 'void *' with an rvalue of type 'enable_if_t<std::is_same<void, intrinsic_t<void *>>::value, void>' (aka 'void')
        PYBIND11_OVERRIDE_PURE(
        ^~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2808:5: note: expanded from macro 'PYBIND11_OVERRIDE_PURE'
    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2770:9: note: expanded from macro 'PYBIND11_OVERRIDE_PURE_NAME'
        PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2736:20: note: expanded from macro 'PYBIND11_OVERRIDE_IMPL'
            return pybind11::detail::cast_safe<ret_type>(std::move(o));                           \
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
Bisecting: 30 revisions left to test after this (roughly 5 steps)
[b22ee64c7309eb7344031b5e5385e6907d84c7eb] Add type_caster<std::monostate> (#3818)
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
Bisecting: 15 revisions left to test after this (roughly 4 steps)
[9969f3b5b5ccad5524a9dab237b551c0ea6359f4] ci: drop win2016 (#3854)
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
example.cpp:18:9: error: cannot initialize return object of type 'void *' with an rvalue of type 'enable_if_t<std::is_same<void, intrinsic_t<void *>>::value, void>' (aka 'void')
        PYBIND11_OVERRIDE_PURE(
        ^~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2808:5: note: expanded from macro 'PYBIND11_OVERRIDE_PURE'
    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2770:9: note: expanded from macro 'PYBIND11_OVERRIDE_PURE_NAME'
        PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2736:20: note: expanded from macro 'PYBIND11_OVERRIDE_IMPL'
            return pybind11::detail::cast_safe<ret_type>(std::move(o));                           \
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
Bisecting: 7 revisions left to test after this (roughly 3 steps)
[65ec5de52fecc974157a0c28490fef61204c39a1] chore: bump changelog for 2.9.2 (#3834)
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
Bisecting: 3 revisions left to test after this (roughly 2 steps)
[ab59f45d2ee05b1df299021b62ab1f59a768e285] Prefer make_caster<T> to type_caster<T> (#3859)
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
Bisecting: 1 revision left to test after this (roughly 1 step)
[e3aa215b020886d648add951186052c619c3cf9d] Add perfect forwarding to make_iterator calls (#3860)
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
Bisecting: 0 revisions left to test after this (roughly 0 steps)
[088ad4f2987d3da4b1ffab376b2b4812fd7634ef] Cleanup cast_safe<void> specialization (#3861)
running  'clang++' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/usr/local/opt/python@3.10/Frameworks/Python.framework/Versions/3.10/include/python3.10' '-I/Users/henryschreiner/git/software/pybind11/include' '-Wno-unused-result' '-Wsign-compare' '-Wunreachable-code' '-fno-common' '-dynamic' '-DNDEBUG' '-g' '-fwrapv' '-O3' '-Wall' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-std=c++11' '-isysroot' '/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk' '-undefined' 'dynamic_lookup' 'example.cpp' '-o' 'example.cpython-310-darwin.so'
example.cpp:18:9: error: cannot initialize return object of type 'void *' with an rvalue of type 'enable_if_t<std::is_same<void, intrinsic_t<void *>>::value, void>' (aka 'void')
        PYBIND11_OVERRIDE_PURE(
        ^~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2808:5: note: expanded from macro 'PYBIND11_OVERRIDE_PURE'
    PYBIND11_OVERRIDE_PURE_NAME(                                                                  \
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2770:9: note: expanded from macro 'PYBIND11_OVERRIDE_PURE_NAME'
        PYBIND11_OVERRIDE_IMPL(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), name, __VA_ARGS__); \
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/henryschreiner/git/software/pybind11/include/pybind11/pybind11.h:2736:20: note: expanded from macro 'PYBIND11_OVERRIDE_IMPL'
            return pybind11::detail::cast_safe<ret_type>(std::move(o));                           \
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
struct override_unused {};
1 error generated.
088ad4f2987d3da4b1ffab376b2b4812fd7634ef is the first bad commit
commit 088ad4f2987d3da4b1ffab376b2b4812fd7634ef
Author: Laramie Leavitt <laramiel@users.noreply.github.com>
Date:   Mon Apr 11 11:57:05 2022 -0700

    Cleanup cast_safe<void> specialization (#3861)

    * Cleanup cast_safe<void> specialization

    Replace explicit specialization of cast_safe<void> with SFINAE.
    It's better for SFINAE cases to cover all type-sets rather than mixing SFINAE and explicit specialization.

    Extracted from #3674

    * [pre-commit.ci] auto fixes from pre-commit.com hooks

    for more information, see https://pre-commit.ci

    * Update cast.h

    Use detail::none_of<> as suggested
struct override_unused {};

  struct override_unused {};
    * [pre-commit.ci] auto fixes from pre-commit.com hooks

    for more information, see https://pre-commit.ci

    * Update cast.h

    Reorder:
    If TEMP_REF
    If VOID
    if (!VOID && !TEMP_REF)

    Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

 include/pybind11/cast.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)
bisect found first bad commit⏎
  // Trampoline use: for reference/pointer types to value-converted values, we do a value cast, then

@EthanSteinberg EthanSteinberg mentioned this issue Oct 22, 2022
Closed
rwgk added a commit to rwgk/pybind11 that referenced this issue Oct 22, 2022
@rwgk
Adding pybind#4117 reproducer to test_virtual_functions.cpp
451158a
rwgk added a commit to rwgk/pybind11 that referenced this issue Oct 22, 2022
@rwgk
Fix and test for issue pybind#4117
554c030
@rwgk rwgk mentioned this issue Oct 22, 2022
Closed
@EthanSteinberg EthanSteinberg mentioned this issue Oct 22, 2022
Merged
@Skylion007 Skylion007 added bug and removed triage New bug, unverified labels Oct 22, 2022
rwgk added a commit to rwgk/pybind11 that referenced this issue Oct 22, 2022
@rwgk
Test from issue pybind#4117
23011bf
@rwgk rwgk mentioned this issue Feb 10, 2023
Closed
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Fix casts to void* EthanSteinberg/pybind11
Fix casts to void* EthanSteinberg/pybind11
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@Skylion007 @henryiii @consolexinhun