https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118538
Bug ID: 118538
Summary: Miscompilation on at -O0 on ARM
Product: gcc
Version: 14.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: disservin.social at gmail dot com
Target Milestone: ---
Created attachment 60196
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=60196&action=edit
reproduction.cpp
The attached reproduction seems to miscompile on ARM, more specifically on a
Raspberry Pi 5.
g++-14 -O0 -std=c++17 -Wall -Wextra -Wpedantic -Wuninitialized
-fno-strict-aliasing -fwrapv -g3 test.cpp && ./a.out
test.cpp: In function ‘int main()’:
test.cpp:55:10: warning: variable ‘reader’ set but not used
[-Wunused-but-set-variable]
55 | auto reader = Reader("file", 1);
| ^~~~~~
[1] 473461 segmentation fault (core dumped) ./a.out
g++-14 -v
Using built-in specs.
COLLECT_GCC=g++-14
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-linux-gnu/14/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: aarch64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
14.2.0-4ubuntu2~24.04' --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=aarch64-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-libquadmath --disable-libquadmath-support
--enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --enable-fix-cortex-a53-843419
--disable-werror
--enable-offload-targets=nvptx-none=/build/gcc-14-KI9fgC/gcc-14-14.2.0/debian/tmp-nvptx/usr
--enable-offload-defaulted --without-cuda-driver --enable-checking=release
--build=aarch64-linux-gnu --host=aarch64-linux-gnu --target=aarch64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.2.0 (Ubuntu 14.2.0-4ubuntu2~24.04)
Running the executable with valgrind mentions an uninitialised value in the
constructor list?
valgrind --track-origins=yes --leak-check=full ./a.out
==476927== Memcheck, a memory error detector
==476927== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==476927== Using Valgrind-3.22.0 and LibVEX; rerun with -h for copyright info
==476927== Command: ./a.out
==476927==
==476927== Conditional jump or move depends on uninitialised value(s)
==476927== at 0x4B65D44: ??? (in /usr/lib/aarch64-linux-gnu/libgcc_s.so.1)
==476927== by 0x4B67697: _Unwind_RaiseException (in
/usr/lib/aarch64-linux-gnu/libgcc_s.so.1)
==476927== by 0x496A8FB: __cxa_throw (in
/usr/lib/aarch64-linux-gnu/libstdc++.so.6.0.33)
==476927== by 0x1096F3: Reader::Reader(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&, int) (test.cpp:43)
==476927== by 0x0: ???
==476927== Uninitialised value was created by a stack allocation
==476927== at 0x109638: Reader::Reader(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&, int) (test.cpp:39)
Removing the file open check from the constructor no longer causes a
segmentation fault...
if (!file.is_open()) {
throw 42;
}
