https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109801
Bug ID: 109801
Summary: -Wmaybe-uninitialized warning with -O1 on move
constructor
Product: gcc
Version: 12.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: szhong at perforce dot com
Target Milestone: ---
Created attachment 55038
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55038&action=edit
preprocessed file
-O1 flag is causing the -Wmaybe-uninitialized warning on move constructor.
testcase:
#include <vector>
template <typename T>
class list
{
public:
list();
~list();
};
template <class T>
class table
{
public:
table()
: buckets_(64), size_(0) {}
table(table&& other) {
std::swap(buckets_, other.buckets_);
std::swap(size_, other.size_);
}
~table() {}
private:
std::vector<list<T> > buckets_;
int size_;
};
int main()
{
table<int> container(std::move(table<int>()));
return (0);
}
$ g++ -v -save-temps -O1 -Wmaybe-uninitialized -c table.cpp
Using built-in specs.
COLLECT_GCC=g++
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap
--enable-languages=c,c++,fortran,lto --prefix=/opt/rh/gcc-toolset-12/root/usr
--mandir=/opt/rh/gcc-toolset-12/root/usr/share/man
--infodir=/opt/rh/gcc-toolset-12/root/usr/share/info
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared
--enable-threads=posix --enable-checking=release --enable-multilib
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
--enable-gnu-unique-object --enable-linker-build-id
--with-gcc-major-version-only --enable-libstdcxx-backtrace
--with-linker-hash-style=gnu --enable-plugin --enable-initfini-array
--with-isl=/builddir/build/BUILD/gcc-12.1.1-20220628/obj-x86_64-redhat-linux/isl-install
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-offload-defaulted --enable-gnu-indirect-function --enable-cet
--with-tune=generic --with-arch_64=x86-64-v2 --with-arch_32=x86-64
--build=x86_64-redhat-linux --with-build-config=bootstrap-lto
--enable-link-serialization=1
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.1.1 20220628 (Red Hat 12.1.1-3) (GCC)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O1' '-Wmaybe-uninitialized' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64-v2'
/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/cc1plus -E
-quiet -v -D_GNU_SOURCE table.cpp -mtune=generic -march=x86-64-v2
-Wmaybe-uninitialized -O1 -fpch-preprocess -o table.ii
ignoring nonexistent directory
"/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/include-fixed"
ignoring nonexistent directory
"/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/../../../../x86_64-redhat-linux/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12
/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/x86_64-redhat-linux
/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/../../../../include/c++/12/backward
/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/include
/usr/local/include
/opt/rh/gcc-toolset-12/root/usr/include
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O1' '-Wmaybe-uninitialized' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64-v2'
/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/cc1plus
-fpreprocessed table.ii -quiet -dumpbase table.cpp -dumpbase-ext .cpp
-mtune=generic -march=x86-64-v2 -O1 -Wmaybe-uninitialized -version -o table.s
GNU C++17 (GCC) version 12.1.1 20220628 (Red Hat 12.1.1-3)
(x86_64-redhat-linux)
compiled by GNU C version 12.1.1 20220628 (Red Hat 12.1.1-3), GMP
version 6.2.0, MPFR version 4.1.0-p9, MPC version 1.2.1, isl version
isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C++17 (GCC) version 12.1.1 20220628 (Red Hat 12.1.1-3)
(x86_64-redhat-linux)
compiled by GNU C version 12.1.1 20220628 (Red Hat 12.1.1-3), GMP
version 6.2.0, MPFR version 4.1.0-p9, MPC version 1.2.1, isl version
isl-0.18-GMP
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 4fe953bdd6603241811586d9fd73a7cb
In file included from
/opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/stl_pair.h:61,
from
/opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/stl_algobase.h:64,
from /opt/rh/gcc-toolset-12/root/usr/include/c++/12/vector:60,
from table.cpp:1:
In function \u2018std::_Require<std::__not_<std::__is_tuple_like<_Tp> >,
std::is_move_constructible<_Tp>, std::is_move_assignable<_Tp> > std::swap(_Tp&,
_Tp&) [with _Tp = int]\u2019,
inlined from \u2018table<T>::table(table<T>&&) [with T = int]\u2019 at
table.cpp:19:18,
inlined from \u2018int main()\u2019 at table.cpp:29:49:
/opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/move.h:204:11: warning:
\u2018container.table<int>::size_\u2019 may be used uninitialized
[-Wmaybe-uninitialized]
204 | _Tp __tmp = _GLIBCXX_MOVE(__a);
| ^~~~~
table.cpp: In function \u2018int main()\u2019:
table.cpp:29:16: note: \u2018container\u2019 declared here
29 | table<int> container(std::move(table<int>()));
| ^~~~~~~~~
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O1' '-Wmaybe-uninitialized' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64-v2'
as -v --64 -o table.o table.s
GNU assembler version 2.38 (x86_64-redhat-linux) using BFD version version
2.38-16.el9
COMPILER_PATH=/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/:/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/:/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/:/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/:/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/
LIBRARY_PATH=/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/:/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/opt/rh/gcc-toolset-12/root/usr/lib/gcc/x86_64-redhat-linux/12/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-O1' '-Wmaybe-uninitialized' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64-v2'
$ cat /etc/os-release
NAME="Red Hat Enterprise Linux"
VERSION="9.1 (Plow)"
ID="rhel"
ID_LIKE="fedora"
VERSION_ID="9.1"
PLATFORM_ID="platform:el9"
PRETTY_NAME="Red Hat Enterprise Linux 9.1 (Plow)"
ANSI_COLOR="0;31"
LOGO="fedora-logo-icon"
CPE_NAME="cpe:/o:redhat:enterprise_linux:9::baseos"
HOME_URL="https://www.redhat.com/";
DOCUMENTATION_URL="https://access.redhat.com/documentation/red_hat_enterprise_linux/9/";
BUG_REPORT_URL="https://bugzilla.redhat.com/";
REDHAT_BUGZILLA_PRODUCT="Red Hat Enterprise Linux 9"
REDHAT_BUGZILLA_PRODUCT_VERSION=9.1
REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux"
REDHAT_SUPPORT_PRODUCT_VERSION="9.1"
