to_stream sets failbit if unable to format

*  If a formatting flag requests data that is not available in
   the Streamable object, or if the Streamable object answers !ok(),
   failbit is set.

include/date/date.h

@@ -4316,28 +4316,33 @@ operator<<(std::basic_ostream<CharT, Traits>& os, const local_time<Duration>& ut
 
 // to_stream
 
+constexpr year nanyear{-32768};
+
 template <class Duration>
 struct fields
 {
-    year_month_day        ymd{year{0}/0/0};
+    year_month_day        ymd{nanyear/0/0};
     weekday               wd{7u};
     time_of_day<Duration> tod{};
+    bool                  has_tod = false;
 
     fields() = default;
 
     fields(year_month_day ymd_) : ymd(ymd_) {}
     fields(weekday wd_) : wd(wd_) {}
-    fields(time_of_day<Duration> tod_) : tod(tod_) {}
+    fields(time_of_day<Duration> tod_) : tod(tod_), has_tod(true) {}
 
     fields(year_month_day ymd_, weekday wd_) : ymd(ymd_), wd(wd_) {}
-    fields(year_month_day ymd_, time_of_day<Duration> tod_) : ymd(ymd_), tod(tod_) {}
+    fields(year_month_day ymd_, time_of_day<Duration> tod_) : ymd(ymd_), tod(tod_),
+                                                              has_tod(true) {}
 
-    fields(weekday wd_, time_of_day<Duration> tod_) : wd(wd_), tod(tod_) {}
+    fields(weekday wd_, time_of_day<Duration> tod_) : wd(wd_), tod(tod_), has_tod(true) {}
 
     fields(year_month_day ymd_, weekday wd_, time_of_day<Duration> tod_)
         : ymd(ymd_)
         , wd(wd_)
         , tod(tod_)
+        , has_tod(true)
         {}
 };
 
@@ -4654,7 +4659,12 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                     os << CharT{'%'} << modified << *fmt;
                 else
                 {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
+                    if (*fmt == 'c' && !fds.has_tod)
+                        os.setstate(std::ios::failbit);
 #if !ONLY_C_LOCALE
+                    if (*fmt == 'c')
                     tm = std::tm{};
                     auto const& ymd = fds.ymd;
                     auto ld = local_days(ymd);
@@ -4713,11 +4723,15 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'C':
             if (command)
             {
+                if (modified == CharT{'O'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.year().ok())
+                        os.setstate(std::ios::failbit);
                     auto y = static_cast<int>(fds.ymd.year());
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'O'})
 #endif
                     {
                         save_stream<CharT, Traits> _(os);
@@ -4743,9 +4757,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 command = nullptr;
                 modified = CharT{};
@@ -4757,11 +4768,15 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'e':
             if (command)
             {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.day().ok())
+                        os.setstate(std::ios::failbit);
                     auto d = static_cast<int>(static_cast<unsigned>(fds.ymd.day()));
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         save_stream<CharT, Traits> _(os);
@@ -4781,9 +4796,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 command = nullptr;
                 modified = CharT{};
@@ -4796,6 +4808,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
                     auto const& ymd = fds.ymd;
                     save_stream<CharT, Traits> _(os);
                     os.fill('0');
@@ -4822,6 +4836,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
                     auto const& ymd = fds.ymd;
                     save_stream<CharT, Traits> _(os);
                     os.fill('0');
@@ -4849,6 +4865,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
                     auto ld = local_days(fds.ymd);
                     auto y = year_month_day{ld + days{3}}.year();
                     auto start = local_days((y - years{1})/date::dec/thu[last]) + (mon-thu);
@@ -4879,11 +4897,15 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'I':
             if (command)
             {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
                     auto hms = fds.tod;
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         if (*fmt == CharT{'I'})
@@ -4900,9 +4922,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -4915,6 +4934,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
                     auto ld = local_days(fds.ymd);
                     auto y = fds.ymd.year();
                     auto doy = ld - local_days(y/jan/1) + days{1};
@@ -4937,11 +4958,15 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'm':
             if (command)
             {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.month().ok())
+                        os.setstate(std::ios::failbit);
                     auto m = static_cast<unsigned>(fds.ymd.month());
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         if (m < 10)
@@ -4956,9 +4981,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -4969,10 +4991,14 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'M':
             if (command)
             {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         if (fds.tod.minutes() < minutes{10})
@@ -4987,9 +5013,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -5017,6 +5040,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
 #if !ONLY_C_LOCALE
                     const CharT f[] = {'%', *fmt};
                     tm.tm_hour = static_cast<int>(fds.tod.hours().count());
@@ -5043,6 +5068,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
 #if !ONLY_C_LOCALE
                     const CharT f[] = {'%', *fmt};
                     tm.tm_hour = static_cast<int>(fds.tod.hours().count());
@@ -5082,6 +5109,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
                     if (fds.tod.hours() < hours{10})
                         os << CharT{'0'};
                     os << fds.tod.hours().count() << CharT{':'};
@@ -5102,10 +5131,14 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'S':
             if (command)
             {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         os << fds.tod.s_;
@@ -5118,9 +5151,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -5148,6 +5178,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             {
                 if (modified == CharT{})
                 {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
                     os << fds.tod;
                 }
                 else
@@ -5162,14 +5194,14 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             break;
         case 'u':
             if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
                 {
                     auto wd = extract_weekday(os, fds);
-                if (os.fail())
-                    return os;
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         os << (wd != 0 ? wd : 7u);
@@ -5182,9 +5214,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -5194,13 +5223,17 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             break;
         case 'U':
             if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
                 {
                     auto const& ymd = fds.ymd;
+                    if (!ymd.ok())
+                        os.setstate(std::ios::failbit);
                     auto ld = local_days(ymd);
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         auto st = local_days(sun[1]/jan/ymd.year());
@@ -5226,9 +5259,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -5239,11 +5269,15 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'V':
             if (command)
             {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.ok())
+                        os.setstate(std::ios::failbit);
                     auto ld = local_days(fds.ymd);
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         auto y = year_month_day{ld + days{3}}.year();
@@ -5271,9 +5305,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -5315,13 +5346,17 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
             break;
         case 'W':
             if (command)
+            {
+                if (modified == CharT{'E'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
                 {
                     auto const& ymd = fds.ymd;
+                    if (!ymd.ok())
+                        os.setstate(std::ios::failbit);
                     auto ld = local_days(ymd);
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'E'})
 #endif
                     {
                         auto st = local_days(mon[1]/jan/ymd.year());
@@ -5347,9 +5382,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -5364,6 +5396,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                     os << CharT{'%'} << modified << *fmt;
                 else
                 {
+                    if (!fds.has_tod)
+                        os.setstate(std::ios::failbit);
 #if !ONLY_C_LOCALE
                     tm = std::tm{};
                     tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
@@ -5388,6 +5422,8 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'y':
             if (command)
             {
+                if (!fds.ymd.year().ok())
+                    os.setstate(std::ios::failbit);
                 auto y = static_cast<int>(fds.ymd.year());
 #if !ONLY_C_LOCALE
                 if (modified == CharT{})
@@ -5415,11 +5451,15 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
         case 'Y':
             if (command)
             {
+                if (modified == CharT{'O'})
+                    os << CharT{'%'} << modified << *fmt;
+                else
+                {
+                    if (!fds.ymd.year().ok())
+                        os.setstate(std::ios::failbit);
                     auto y = fds.ymd.year();
 #if !ONLY_C_LOCALE
                     if (modified == CharT{})
-#else
-                if (modified != CharT{'O'})
 #endif
                     {
                         os << y;
@@ -5432,9 +5472,6 @@ to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt,
                         facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                     }
 #endif
-                else
-                {
-                    os << CharT{'%'} << modified << *fmt;
                 }
                 modified = CharT{};
                 command = nullptr;
@@ -5572,7 +5609,7 @@ std::basic_ostream<CharT, Traits>&
 to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const month& m)
 {
     using CT = std::chrono::seconds;
-    fields<CT> fds{m/0/0};
+    fields<CT> fds{m/0/nanyear};
     return to_stream(os, fmt, fds);
 }
 
@@ -5582,7 +5619,7 @@ std::basic_ostream<CharT, Traits>&
 to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const day& d)
 {
     using CT = std::chrono::seconds;
-    fields<CT> fds{d/0/0};
+    fields<CT> fds{d/0/nanyear};
     return to_stream(os, fmt, fds);
 }
 
@@ -5612,7 +5649,7 @@ std::basic_ostream<CharT, Traits>&
 to_stream(std::basic_ostream<CharT, Traits>& os, const CharT* fmt, const month_day& md)
 {
     using CT = std::chrono::seconds;
-    fields<CT> fds{md/0};
+    fields<CT> fds{md/nanyear};
     return to_stream(os, fmt, fds);
 }
 

test/date_test/format/range.pass.cpp

@@ -69,10 +69,10 @@ main()
     assert(os.str() == "32767-12-31 00:00:01.2096");
     os.str("");
 
-    os << format("%F %T", jan/1/year::min());
+    os << format("%F", jan/1/year::min());
-    assert(os.str() == "-32767-01-01 00:00:00");
+    assert(os.str() == "-32767-01-01");
     os.str("");
-    os << format("%F %T", dec/last/year::max());
+    os << format("%F", dec/last/year::max());
-    assert(os.str() == "32767-12-31 00:00:00");
+    assert(os.str() == "32767-12-31");
     os.str("");
 }