[Bug libstdc++/110968] New: format out of bounds read on format("{:05L}",-1.f)

[gcc at pauldreik dot se via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110968

            Bug ID: 110968
           Summary: format out of bounds read on format("{:05L}",-1.f)
           Product: gcc
           Version: 13.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at pauldreik dot se
  Target Milestone: ---

The following program:

#include <cstdio>
#include <format>

int main() {
    float v = -1;
    std::puts(std::vformat("{:05L}", std::make_format_args(v)).c_str());
}

generates an out of bounds read when compiled with gcc 13.2 (and current trunk,
as of 2023-08-10).

Link to reproducer: https://godbolt.org/z/PjeTsK89E