This is a quick and dirty fix for this gcc-13 build failure on ppc64el with -O3 optimization level:
/usr/bin/g++-13 -DCPUSTRING=\"ppc64el\" -DUSE_DOOMCLASSIC -DUSE_EXCEPTIONS -DUSE_FFMPEG -DUSE_NEWER_JPEG -DUSE_OPENAL -D__DOOM__ -I/usr/include/imgui -I/usr/include/stb -I/<<PKGBUILDDIR>>/neo/. -I/<<PKGBUILDDIR>>/neo/idlib -isystem /usr/include/SDL2 -g -O3 -ffile-prefix-map=/<<PKGBUILDDIR>>=. -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -fno-stack-clash-protection -fdebug-prefix-map=/<<PKGBUILDDIR>>=/usr/src/rbdoom3bfg-1.4.0+dfsg-3ubuntu2 -Wdate-time -D_FORTIFY_SOURCE=3 -std=c++11 -pipe -Werror=format-security -Werror=format -Wno-pragmas -Wno-unused-variable -Wno-switch -Wno-unused-value -Winvalid-pch -Wno-multichar -fno-strict-aliasing -MD -MT CMakeFiles/rbdoom3bfg.dir/sys/Snapshot_Jobs.cpp.o -MF CMakeFiles/rbdoom3bfg.dir/sys/Snapshot_Jobs.cpp.o.d -o CMakeFiles/rbdoom3bfg.dir/sys/Snapshot_Jobs.cpp.o -c /<<PKGBUILDDIR>>/neo/sys/Snapshot_Jobs.cpp
In file included from /usr/include/string.h:548,
from /<<PKGBUILDDIR>>/neo/idlib/sys/sys_includes.h:141,
from /<<PKGBUILDDIR>>/neo/idlib/precompiled.h:34,
from /<<PKGBUILDDIR>>/neo/sys/PacketProcessor.cpp:29:
In function ‘memcpy’,
inlined from ‘idDataQueue<64, 8000>::Append(int, unsigned char const*, int, unsigned char const*, int)’ at /<<PKGBUILDDIR>>/neo/idlib/../idlib/DataQueue.h:112:8,
inlined from ‘idPacketProcessor::VerifyEmptyReliableQueue(unsigned char, unsigned char)’ at /<<PKGBUILDDIR>>/neo/sys/PacketProcessor.cpp:660:16:
/usr/include/powerpc64le-linux-gnu/bits/string_fortified.h:29:33: error: argument 2 null where non-null expected [-Werror=nonnull]
29 | return __builtin___memcpy_chk (__dest, __src, __len,
| ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
30 | __glibc_objsize0 (__dest));
| ~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/powerpc64le-linux-gnu/bits/string_fortified.h:29:33: note: in a call to built-in function ‘__memcpy_chk’
cc1plus: some warnings being treated as errors
