[Bug middle-end/105400] g++-11 regression produces -Warray-bounds false positive warning with -O2

[laurent.pinchart at ideasonboard dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105400

--- Comment #3 from Laurent Pinchart <laurent.pinchart at ideasonboard dot com> ---
Created attachment 52911
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52911&action=edit
Original preprocessed sources

Here's the full preprocessed source, corresponding to
https://git.libcamera.org/libcamera/libcamera.git/tree/src/libcamera/base/object.cpp,
generated with

$ g++-11.2.1 -v -save-temps -Isrc/libcamera/base/libcamera-base.so.0.0.0.p
-Isrc/libcamera/base -I../../src/libcamera/base -Iinclude -I../../include
-fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch
-Wnon-virtual-dtor -Wextra -Werror -std=c++17 -O3 -Wshadow -include config.h
-fPIC -pthread -DLIBCAMERA_BASE_PRIVATE -MD -MQ
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o -MF
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o.d -o
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o -c
../../src/libcamera/base/object.cpp
Using built-in specs.
COLLECT_GCC=g++-11.2.1
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-11.2.1_p20220115/work/gcc-11-20220115/configure
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/11.2.1
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/11.2.1
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/11.2.1/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/11.2.1/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include/g++-v11
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/11.2.1/python
--enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt
--disable-werror --with-system-zlib --enable-nls --without-included-gettext
--disable-libunwind-exceptions --enable-checking=yes
--with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo
11.2.1_p20220115 p4' --disable-esp --enable-libstdcxx-time
--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 --disable-cet
--disable-systemtap --disable-valgrind-annotations --disable-vtable-verify
--disable-libvtv --without-zstd --enable-lto --with-isl
--disable-isl-version-check --enable-default-pie --enable-default-ssp
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 11.2.1 20220115 (Gentoo 11.2.1_p20220115 p4) 
COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-v' '-save-temps' '-I'
'src/libcamera/base/libcamera-base.so.0.0.0.p' '-I' 'src/libcamera/base' '-I'
'../../src/libcamera/base' '-I' 'include' '-I' '../../include' '-D'
'_FILE_OFFSET_BITS=64' '-Wall' '-Winvalid-pch' '-Wnon-virtual-dtor' '-Wextra'
'-Werror' '-std=c++17' '-O3' '-Wshadow' '-include' 'config.h' '-fPIC'
'-pthread' '-D' 'LIBCAMERA_BASE_PRIVATE' '-MD' '-MQ'
'src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o' '-MF'
'src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o.d' '-o'
'src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64' '-dumpdir'
'src/libcamera/base/libcamera-base.so.0.0.0.p/'
 /usr/libexec/gcc/x86_64-pc-linux-gnu/11.2.1/cc1plus -E -quiet -v -I
src/libcamera/base/libcamera-base.so.0.0.0.p -I src/libcamera/base -I
../../src/libcamera/base -I include -I ../../include -MD
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.d -MF
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o.d -MQ
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o -D_GNU_SOURCE
-D_REENTRANT -D _FILE_OFFSET_BITS=64 -D LIBCAMERA_BASE_PRIVATE -include
config.h ../../src/libcamera/base/object.cpp -mtune=generic -march=x86-64
-std=c++17 -Wall -Winvalid-pch -Wnon-virtual-dtor -Wextra -Werror -Wshadow
-fdiagnostics-color=always -fPIC -O3 -fpch-preprocess -o
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.ii
ignoring nonexistent directory
"/usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/../../../../x86_64-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 src/libcamera/base/libcamera-base.so.0.0.0.p
 src/libcamera/base
 ../../src/libcamera/base
 include
 ../../include
 /usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include/g++-v11
 /usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include/g++-v11/x86_64-pc-linux-gnu
 /usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include/g++-v11/backward
 /usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include
 /usr/local/include
 /usr/lib/gcc/x86_64-pc-linux-gnu/11.2.1/include-fixed
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-v' '-save-temps' '-I'
'src/libcamera/base/libcamera-base.so.0.0.0.p' '-I' 'src/libcamera/base' '-I'
'../../src/libcamera/base' '-I' 'include' '-I' '../../include' '-D'
'_FILE_OFFSET_BITS=64' '-Wall' '-Winvalid-pch' '-Wnon-virtual-dtor' '-Wextra'
'-Werror' '-std=c++17' '-O3' '-Wshadow' '-include' 'config.h' '-fPIC'
'-pthread' '-D' 'LIBCAMERA_BASE_PRIVATE' '-MD' '-MQ'
'src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o' '-MF'
'src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o.d' '-o'
'src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.o' '-c'
'-shared-libgcc' '-mtune=generic' '-march=x86-64' '-dumpdir'
'src/libcamera/base/libcamera-base.so.0.0.0.p/'
 /usr/libexec/gcc/x86_64-pc-linux-gnu/11.2.1/cc1plus -fpreprocessed
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.ii -quiet -dumpdir
src/libcamera/base/libcamera-base.so.0.0.0.p/ -dumpbase object.cpp.cpp
-dumpbase-ext .cpp -mtune=generic -march=x86-64 -O3 -Wall -Winvalid-pch
-Wnon-virtual-dtor -Wextra -Werror -Wshadow -std=c++17 -version
-fdiagnostics-color=always -fPIC -o
src/libcamera/base/libcamera-base.so.0.0.0.p/object.cpp.s
GNU C++17 (Gentoo 11.2.1_p20220115 p4) version 11.2.1 20220115
(x86_64-pc-linux-gnu)
        compiled by GNU C version 11.2.1 20220115, GMP version 6.2.1, MPFR
version 4.1.0-p13, MPC version 1.2.1, isl version isl-0.24-GMP

GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU C++17 (Gentoo 11.2.1_p20220115 p4) version 11.2.1 20220115
(x86_64-pc-linux-gnu)
        compiled by GNU C version 11.2.1 20220115, GMP version 6.2.1, MPFR
version 4.1.0-p13, MPC version 1.2.1, isl version isl-0.24-GMP

GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: 8c115abe653dbf0f6d87498ebb5d37f4
In file included from ../../src/libcamera/base/object.cpp:13:
../../include/libcamera/base/message.h: In member function ‘void
libcamera::Object::notifyThreadMove()’:
../../include/libcamera/base/message.h:58:47: error: array subscript ‘const
libcamera::InvokeMessage[0]’ is partly outside array bounds of
‘libcamera::Message [1]’ [-Werror=array-bounds]
   58 |         Semaphore *semaphore() const { return semaphore_; }
      |                                               ^~~~~~~~~~
../../src/libcamera/base/object.cpp:280:17: note: while referencing ‘msg’
  280 |         Message msg(Message::ThreadMoveMessage);
      |                 ^~~
cc1plus: all warnings being treated as errors