[libcxx-commits] [libcxx] [libc++][chrono] Fix streaming for unsigned durations. (PR #97889)

[Mark de Wever via libcxx-commits]

https://github.com/mordante created https://github.com/llvm/llvm-project/pull/97889

This fixes formatting for durations using the unsigned types unsigned short, unsigned, unsigned long, and unsigned long long. It does not allow the unsigned char type. Since the formatting function uses ostream::operator<< this type probably does not what it should do.

Note that based on the standard all artithemetic types are allowed, including bool, char, wchar_t. These types are not implemented either. Allowing them seems like a defect in the Standard.

No effort is done to support user-defined types; the wording in the Standard is unclear regarding the constrains for these types.

Fixes https://github.com/llvm/llvm-project/issues/96820

>From b0a380193230f0cb935102b6e2702d98bd795d72 Mon Sep 17 00:00:00 2001
From: Mark de Wever <koraq at xs4all.nl>
Date: Sat, 6 Jul 2024 13:11:27 +0200
Subject: [PATCH] [libc++][chrono] Fix streaming for unsigned durations.

This fixes formatting for durations using the unsigned types
unsigned short, unsigned, unsigned long, and unsigned long long. It does
not allow the unsigned char type. Since the formatting function uses
ostream::operator<< this type probably does not what it should do.

Note that based on the standard all artithemetic types are allowed,
including bool, char, wchar_t. These types are not implemented either.
Allowing them seems like a defect in the Standard.

No effort is done to support user-defined types; the wording in the
Standard is unclear regarding the constrains for these types.

Fixes https://github.com/llvm/llvm-project/issues/96820
---
 libcxx/include/__chrono/formatter.h           | 12 ++++++---
 .../time.duration.nonmember/ostream.pass.cpp  | 25 +++++++++++++++++++
 .../time/time.syn/formatter.duration.pass.cpp | 12 +++++++++
 3 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/libcxx/include/__chrono/formatter.h b/libcxx/include/__chrono/formatter.h
index e9b81c3de8a70..22694eb3bd083 100644
--- a/libcxx/include/__chrono/formatter.h
+++ b/libcxx/include/__chrono/formatter.h
@@ -46,6 +46,7 @@
 #include <__memory/addressof.h>
 #include <cmath>
 #include <ctime>
+#include <limits>
 #include <sstream>
 #include <string_view>
 
@@ -589,9 +590,14 @@ __format_chrono(const _Tp& __value,
     __sstr << __value;
   else {
     if constexpr (chrono::__is_duration<_Tp>::value) {
-      if (__value < __value.zero())
-        __sstr << _CharT('-');
-      __formatter::__format_chrono_using_chrono_specs(__sstr, chrono::abs(__value), __chrono_specs);
+      if constexpr (numeric_limits<typename _Tp::rep>::is_signed) {
+        if (__value < __value.zero()) {
+          __sstr << _CharT('-');
+          __formatter::__format_chrono_using_chrono_specs(__sstr, -__value, __chrono_specs);
+        } else
+          __formatter::__format_chrono_using_chrono_specs(__sstr, __value, __chrono_specs);
+      } else
+        __formatter::__format_chrono_using_chrono_specs(__sstr, __value, __chrono_specs);
       // TODO FMT When keeping the precision it will truncate the string.
       // Note that the behaviour what the precision does isn't specified.
       __specs.__precision_ = -1;
diff --git a/libcxx/test/std/time/time.duration/time.duration.nonmember/ostream.pass.cpp b/libcxx/test/std/time/time.duration/time.duration.nonmember/ostream.pass.cpp
index e5d11ab4672bd..aecb96b58719e 100644
--- a/libcxx/test/std/time/time.duration/time.duration.nonmember/ostream.pass.cpp
+++ b/libcxx/test/std/time/time.duration/time.duration.nonmember/ostream.pass.cpp
@@ -216,10 +216,35 @@ static void test_units() {
   assert(stream_ja_JP_locale<CharT>(std::chrono::duration<int, std::ratio<11, 9>>(0)) == SV("0[11/9]s"));
 }
 
+template <class CharT>
+static void test_unsigned_types() {
+  // Reported in https://github.com/llvm/llvm-project/issues/96820
+  using namespace std::literals::chrono_literals;
+
+  // C locale
+  assert(stream_c_locale<CharT>(std::chrono::duration<unsigned short, std::atto>(0)) == SV("0as"));
+  assert(stream_c_locale<CharT>(std::chrono::duration<unsigned, std::femto>(0)) == SV("0fs"));
+  assert(stream_c_locale<CharT>(std::chrono::duration<unsigned long, std::pico>(0)) == SV("0ps"));
+  assert(stream_c_locale<CharT>(std::chrono::duration<unsigned long long, std::nano>(0)) == SV("0ns"));
+
+  // fr_FR locale
+  assert(stream_fr_FR_locale<CharT>(std::chrono::duration<unsigned short, std::atto>(0)) == SV("0as"));
+  assert(stream_fr_FR_locale<CharT>(std::chrono::duration<unsigned, std::femto>(0)) == SV("0fs"));
+  assert(stream_fr_FR_locale<CharT>(std::chrono::duration<unsigned long, std::pico>(0)) == SV("0ps"));
+  assert(stream_fr_FR_locale<CharT>(std::chrono::duration<unsigned long long, std::nano>(0)) == SV("0ns"));
+
+  // ja_JP locale
+  assert(stream_ja_JP_locale<CharT>(std::chrono::duration<unsigned short, std::atto>(0)) == SV("0as"));
+  assert(stream_ja_JP_locale<CharT>(std::chrono::duration<unsigned, std::femto>(0)) == SV("0fs"));
+  assert(stream_ja_JP_locale<CharT>(std::chrono::duration<unsigned long, std::pico>(0)) == SV("0ps"));
+  assert(stream_ja_JP_locale<CharT>(std::chrono::duration<unsigned long long, std::nano>(0)) == SV("0ns"));
+}
+
 template <class CharT>
 static void test() {
   test_values<CharT>();
   test_units<CharT>();
+  test_unsigned_types<CharT>();
 }
 
 int main(int, char**) {
diff --git a/libcxx/test/std/time/time.syn/formatter.duration.pass.cpp b/libcxx/test/std/time/time.syn/formatter.duration.pass.cpp
index dbf373a19ba80..b503d8ecc2817 100644
--- a/libcxx/test/std/time/time.syn/formatter.duration.pass.cpp
+++ b/libcxx/test/std/time/time.syn/formatter.duration.pass.cpp
@@ -1157,12 +1157,24 @@ static void test_pr62082() {
   check(SV("00.111111"), SV("{:%S}"), std::chrono::duration<long double, std::ratio<1, 9>>{1});
 }
 
+template <class CharT>
+static void test_unsigned_duration() {
+  // Reported in https://github.com/llvm/llvm-project/issues/96820
+  using namespace std::literals::chrono_literals;
+
+  check(SV("1as"), SV("{}"), std::chrono::duration<unsigned short, std::atto>(500));
+  check(SV("1fs"), SV("{}"), std::chrono::duration<unsigned, std::femto>(1));
+  check(SV("1ps"), SV("{}"), std::chrono::duration<unsigned long, std::pico>(1));
+  check(SV("1ns"), SV("{}"), std::chrono::duration<unsigned long long, std::nano>(1));
+}
+
 template <class CharT>
 static void test() {
   using namespace std::literals::chrono_literals;
 
   test_no_chrono_specs<CharT>();
   test_valid_values<CharT>();
+  test_unsigned_duration<CharT>();
   test_pr62082<CharT>();
 
   check_invalid_types<CharT>(