https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109180
Bug ID: 109180
Summary: Explicit template instantiation doesn't work for
constexpr destructors on arm32 when optimizations are
enabled
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: idhameed at protonmail dot com
Target Milestone: ---
Example (compile with "g++ -std=c++20 -O -c"):
===========================================
template <typename t>
struct record {
constexpr ~record() { }
};
inline record<char>
return_record() { return {}; }
template record<char>::~record();
===========================================
Compiler Explorer: https://godbolt.org/z/j37rvr961
GCC 10+ targeting 32-bit ARM won't emit any symbols for record<char>::~record
when using most -O levels (-O, -O2, -O3, -Ofast, -Og). Using -fno-inline--or
placing the explicit instantiation of record<char>::~record above the
definition of return_record--works around this bug and causes a symbol for
record<char>::~record to be emitted, as I'd expect. x86-64 GCC doesn't have
this problem.
The original, non-minimized problem I encountered: GCC 12.2.0 as a
cross-compiler on an x86-64 host targeting arm-linux-gnueabihf can't be used to
compile and link LLVM 15's libc++, because libc++'s implementation of
std::basic_string has code that fits the aformentioned pattern--there's an
overload of `std::__1::literals::string_literals::operator "" s` that returns a
basic_string<char>. I tried the release/15.x branch of llvm-project at commit
92e7ef99303f8f367f279ccfa2393e4b96db915a.
