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)
