https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95349
Bug ID: 95349
Summary: Using std::launder(p) produces unexpected behavior
where (p) produces expected behavior
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: andrew2085 at gmail dot com
Target Milestone: ---
Created attachment 48609
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48609&action=edit
preprocessed ii file
All of these f1/f2/f3 functions should do the same thing, essentially the same
thing as std::start_lifetime_as. Since the return value of placement new is
used, std::launder is not necessary here, but using it anyway produces
unexpected behavior when it should do nothing at all. Every version of gcc and
every system I've tried has produced the same result.
Here's the original source for reference: https://godbolt.org/z/zdQsfV
gcc version: 10.1.0 (All other versions tested produce same behavior)
system: Arch Linux x86_64
compile command: g++ -save-temps -std=c++17 -O2 -fno-stack-protector
-fstrict-aliasing main.cpp && ./a.out
configure options: g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --with-isl
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id
--enable-lto --enable-multilib --enable-plugin --enable-shared
--enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-libunwind-exceptions --disable-werror
gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.1.0 (GCC)
