public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c++/115050] New: Segfault when compiled with -O0
@ 2024-05-12 11:40 lobel.krivic at proton dot me
  2024-05-12 11:44 ` [Bug c++/115050] " pinskia at gcc dot gnu.org
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: lobel.krivic at proton dot me @ 2024-05-12 11:40 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115050

            Bug ID: 115050
           Summary: Segfault when compiled with -O0
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lobel.krivic at proton dot me
  Target Milestone: ---

Created attachment 58183
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58183&action=edit
the preprocessed file

The following source code:
```
#include <cstddef>
#include <type_traits>
#include <utility>
#include <exception>

///////////////////////////////////////////////////////

class VTable
{
  public:
        virtual void func(int x) = 0; // #1 this line affects behavior
        virtual ~VTable() = default;
};

template <typename T>
class Handler final : public VTable
{
  private:
        static constexpr int S = sizeof(void*);
        std::byte _data[S];

  public:
        template <typename... CArgs>
        Handler(CArgs&&... args) {
                static_assert(sizeof(T) <= S);
                ::new (&_data[0]) T(std::forward<CArgs>(args)...);
        }

        void func(int) { return; }

        ~Handler() { static_cast<T*>(static_cast<void*>(&_data[0]))->~T(); }
};

///////////////////////////////////////////////////////

struct FBase
{
        static constexpr int S = sizeof(void*) + sizeof(VTable);
        std::byte _data[S];

        ~FBase() {
static_cast<VTable*>(static_cast<void*>(&_data[0]))->~VTable(); } // #2 this
line affects behavior
};

struct F : FBase
{
        template <typename T>
        F(T&& t) {
                static_assert(sizeof(Handler<std::decay_t<T>>) <= S);
                ::new (&_data[0]) Handler<std::decay_t<T>>(std::forward<T>(t));
        }

        ~F() = default;
};

///////////////////////////////////////////////////////

struct Testor
{
        Testor() = default;
        ~Testor() = default;

        Testor(const Testor& /*unused*/) { throw std::bad_exception(); }
};

///////////////////////////////////////////////////////

#include <iostream>

int main() {

        try {
                Testor testor;
                F f{testor};
        }
        catch (const std::bad_exception& e) {
                std::cout << " caught! " << e.what() << std::endl;
        }

        return 0;
}
```

segfaults on runtime when compiled with -O0 but works when compiled with
-O1/O2/O3. This happens on all versions of gcc from 11.1 to 14.1 (clang does
not have this problem). -Wall and -Wextra do not report anything.
Here is the link to the source code: https://godbolt.org/z/5dWKEenMM

The complete command line that triggers the bug:
`g++ -O0 ./bug.cpp -o ./bug.out && ./bug.out`

Bug report that may be related:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50239


Output of `gcc -v`:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/13/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-13.2.1_p20240113-r1/work/gcc-13-20240113/configure
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gn
u --prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/13
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/13/include
--datadir=/usr/share/gcc-data/x86_
64-pc-linux-gnu/13 --mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/13/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/13/info --with-gxx-include-
dir=/usr/lib/gcc/x86_64-pc-linux-gnu/13/include/g++-v13 --disable-silent-rules
--disable-dependency-tracking --with-python-dir=/share/gcc-data/x86_64-pc
-linux-gnu/13/python --enable-languages=c,c++,fortran --enable-obsolete
--enable-secureplt --disable-werror --with-system-zlib --disable-nls
--disable-l
ibunwind-exceptions --enable-checking=release
--with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo
13.2.1_p20240113-r1 p12' --with-gcc-major
-version-only --enable-libstdcxx-time --enable-lto --disable-libstdcxx-pch
--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 --disa
ble-cet --disable-systemtap --disable-valgrind-annotations
--disable-vtable-verify --disable-libvtv --without-zstd --without-isl
--enable-default-pie --
enable-default-ssp --disable-fixincludes
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 13.2.1 20240113 (Gentoo 13.2.1_p20240113-r1 p12)

^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-05-28 21:43 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-05-12 11:40 [Bug c++/115050] New: Segfault when compiled with -O0 lobel.krivic at proton dot me
2024-05-12 11:44 ` [Bug c++/115050] " pinskia at gcc dot gnu.org
2024-05-12 15:50 ` sjames at gcc dot gnu.org
2024-05-28 21:43 ` pinskia at gcc dot gnu.org

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).