[Bug libstdc++/116657] New: tzdata 2024b causing timezone parsing issues in std::chrono

[toolybird at tuta dot io via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116657

            Bug ID: 116657
           Summary: tzdata 2024b causing timezone parsing issues in
                    std::chrono
           Product: gcc
           Version: 14.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: toolybird at tuta dot io
  Target Milestone: ---

Hi, it seems latest tzdata-2024b is causing some apps to misbehave. This
reproducer (shamelessly borrowed from
https://github.com/llvm/llvm-project/issues/107779) demonstrates the issue:

#include <chrono>
#include <iostream>

int main() {
  std::cout << std::chrono::get_tzdb().current_zone()->name() << "\n";
  return 0;
}

$ g++ -std=c++20 foo.cpp -o foo

With tzdata-2024a it correctly prints the local timezone. With tzdata-2024b it
displays "Etc/UTC"

$ g++ --version
g++ (GCC) 14.2.1 20240805

Arch Linux x86_64

Note: AFAICT Arch is using the standard "main" format for the tzdata (not
"rearguard" or "vanguard").

Apologies for not testing latest GCC trunk! If it works there, it would be
awesome to have the patch applied to the gcc-14 branch. Thanks!