commit c6b7ba5d993d6f7240793c2fa9b55a99f6ee7d36
author Tomáš Pecka <tomas.pecka@cesnet.cz> Fri Apr 07 10:01:29 2023 +0200
committer Jan Kundrát <jan.kundrat@cesnet.cz> Tue Apr 11 11:13:08 2023 +0200
tree 16e5d77ffc2368ae5f5fa29963363025f4da43f4
parent f7ba1e8ada1edea5857af79b041c2efb8d7e4148

workaround gcc compiler bug

There is a regression in gcc since version 12.0 to at least 12.2.1 that
causes gcc to emit incorrect machine code.

Code like

  std::optional<int> o1;
  try {
    o1 = foo(); // foo can throw
  } catch(...) {
    process(o1);
  }

  std::optional<double> o2{o1};
  bar(o2);

may trigger -Wmaybe-uninitialized with -O2 optimization and the call
process(o1) results in the store for variable o1 removed which makes
the valgrind report uninitialized values (see [1]).

Interestingly, we can work around the bug by setting both std::optional
to contain the same type. I prefer altering our code a bit so our code
is compiled correctly by even by gcc versions that contain this
unfortunate regression.

Thanks Petr Gotthard for discovering the possible crash in our code.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109434

Bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109434
Change-Id: I29d73533b8a8550aeb7f6f0b92b5287021a4f193
Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz>