https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121929
Bug ID: 121929
Summary: std::format prints a valid-looking date for invalid
2020y/January/Friday[10]
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
CC: tkaminsk at gcc dot gnu.org
Target Milestone: ---
#include <chrono>
#include <format>
#include <iostream>
int main() {
using namespace std::chrono;
auto d = 2020y/January/Friday[10];
std::cout << local_days(d) - local_days(2020y/January/0) << std::endl; //
"66d"
std::cout << std::format("{:%Y-%m-%d}", d) << std::endl;
// prints: "2020-01-06"
// should print: "2020-01-66"
}
Tomasz writes:
The value of month is fixed, and priting a valid date out of that seems just
wrong. We should turn !okweekoffset into !ok date. Which would not be more
expensive nor harder, just compute day using:
t._M_ldays - local_days(t._M_year/t._M_month/0)
Instead of:
year_month_day(t.Mldays).day()
