https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119260
Bug ID: 119260
Summary: reinterpret_cast function pointer to integer and
applying and incorrectly calculated
Product: gcc
Version: 14.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: geza.herman at gmail dot com
Target Milestone: ---
Look at this simple program:
#include <cstdint>
#include <cstdio>
void fn() {
}
int main() {
const uintptr_t f = reinterpret_cast<uintptr_t>(&fn);
printf("%tx %td\n", f, f&1);
}
When compiling it without optimization, and fn's address is odd, f&1 evaluates
0 (but this should be 1). For example, this is an example output on my system:
55cc3e32e139 0
(If fn's address happens to be even, then try to add another empty function).
If I remove "const", the bug disappears. Also if I use (f&3), or other larger
bit masks, things seems to work correctly.
I managed to reproduce this problem with gcc 10, 11, 12, 13, 14 and 15.
Repro on godbolt: https://godbolt.org/z/Yczxca5dq
"g++-14 -v" prints:
Using built-in specs.
COLLECT_GCC=g++-14
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-linux-gnu/14/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 14.2.0-8'
--with-bugurl=file:///usr/share/doc/gcc-14/README.Bugs
--enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2,rust --prefix=/usr
--with-gcc-major-version-only --program-suffix=-14
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/libexec --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-libstdcxx-backtrace
--enable-gnu-unique-object --disable-vtable-verify --enable-plugin
--enable-default-pie --with-system-zlib --enable-libphobos-checking=release
--with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch
--disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none=/build/reproducible-path/gcc-14-14.2.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/reproducible-path/gcc-14-14.2.0/debian/tmp-gcn/usr
--enable-offload-defaulted --without-cuda-driver --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-serialization=3
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.2.0 (Debian 14.2.0-8)
