[committed] libstdc++: Fix how chrono::parse handles errors for time-of-day values

[Jonathan Wakely <jwakely@redhat.com>]

Tested x86_64-linux. Pushed to trunk.

-- >8 --

We fail to diagnose an error and extract an incorrect time for cases
like "25:59" >> parse("%H:%M", mins). The bad "25" hour value gets
ignored (on the basis that we might not care about it if trying to
extract something like a weekday or a month name), but then when we get
to the end of the function we think we have a valid time from "59" and
so the result is 00:59.

The problem is that the '__bad_h' value is used for "no hour value read
yet" as well as "bad hour value read". If we just set __h = __bad_h and
continue, we can't tell later that we read an invalid hour.

The fix is to set failbit early when we're trying to extract a
time-of-day (e.g. duration or time_point) and we encounter an invalid
hour, minute, or second value. We can still delay other error checking
to the end.

libstdc++-v3/ChangeLog:

	* include/bits/chrono_io.h (_Parser::operator()): Set failbit
	early if invalid values are read when _M_need & _TimeOfDay is
	non-zero.
	* testsuite/std/time/parse.cc: Check that "25:59" cannot be
	parsed for "%H:%M".
---
 libstdc++-v3/include/bits/chrono_io.h    | 53 +++++++++++++-----------
 libstdc++-v3/testsuite/std/time/parse.cc |  7 ++++
 2 files changed, 36 insertions(+), 24 deletions(-)

diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index f359571b4db..7352df095ff 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -3327,7 +3327,16 @@ namespace __detail
 			  __h = __bad_h;
 			}
 		      else if (__c == 'H' && __val >= 0 && __val <= 23)
-			__h = hours(__val);
+			{
+			  __h = hours(__val);
+			  __h12 = __bad_h;
+			}
+		      else
+			{
+			  if (_M_need & _ChronoParts::_TimeOfDay)
+			    __err |= ios_base::failbit;
+			  break;
+			}
 		    }
 		  __parts |= _ChronoParts::_TimeOfDay;
 		  break;
@@ -3392,9 +3401,8 @@ namespace __detail
 			__min = minutes(__val);
 		      else
 			{
-			  __h = __bad_h;
-			  __min = __bad_min;
-			  __s = __bad_sec;
+			  if (_M_need & _ChronoParts::_TimeOfDay)
+			    __err |= ios_base::failbit;
 			  break;
 			}
 		    }
@@ -3481,33 +3489,31 @@ namespace __detail
 		  else
 		    {
 		      auto __val = __read_unsigned(2);
-		      if (__val == -1 || __val > 23)
+		      if (__val == -1 || __val > 23) [[unlikely]]
 			{
-			  __h = __bad_h;
-			  __min = __bad_min;
-			  __s = __bad_sec;
-			  break;
-			}
-		      if (!__read_chr(':'))
-			{
-			  __err |= ios_base::failbit;
+			  if (_M_need & _ChronoParts::_TimeOfDay)
+			    __err |= ios_base::failbit;
 			  break;
 			}
+		      if (!__read_chr(':')) [[unlikely]]
+			break;
 		      __h = hours(__val);
 
 		      __val = __read_unsigned(2);
-		      if (__val == -1 || __val > 60)
+		      if (__val == -1 || __val > 60) [[unlikely]]
 			{
-			  __h = __bad_h;
-			  __min = __bad_min;
-			  __s = __bad_sec;
+			  if (_M_need & _ChronoParts::_TimeOfDay)
+			    __err |= ios_base::failbit;
 			  break;
 			}
 		      __min = minutes(__val);
 
-		      __parts |= _ChronoParts::_TimeOfDay;
-
-		      if (__c != 'T' || !__read_chr(':'))
+		      if (__c == 'R')
+			{
+			  __parts |= _ChronoParts::_TimeOfDay;
+			  break;
+			}
+		      else if (!__read_chr(':')) [[unlikely]]
 			break;
 		    }
 		  [[fallthrough]];
@@ -3527,13 +3533,12 @@ namespace __detail
 						   ratio<1>>)
 		    {
 		      auto __val = __read_unsigned(__num ? __num : 2);
-		      if (0 <= __val && __val <= 59)
+		      if (0 <= __val && __val <= 59) [[likely]]
 			__s = seconds(__val);
 		      else
 			{
-			  __h = __bad_h;
-			  __min = __bad_min;
-			  __s = __bad_sec;
+			  if (_M_need & _ChronoParts::_TimeOfDay)
+			    __err |= ios_base::failbit;
 			  break;
 			}
 		    }
diff --git a/libstdc++-v3/testsuite/std/time/parse.cc b/libstdc++-v3/testsuite/std/time/parse.cc
index 46eb7f28c85..86222d59596 100644
--- a/libstdc++-v3/testsuite/std/time/parse.cc
+++ b/libstdc++-v3/testsuite/std/time/parse.cc
@@ -252,6 +252,13 @@ test_errors()
   VERIFY( is.eof() && ! is.fail() );
   VERIFY( y == 2010y );
 
+  min = -1min;
+  is.clear();
+  is.str("25:59");
+  is >> parse("%H:%M", min); // 25h is out of range and needed
+  VERIFY( is.fail() );
+  VERIFY( min == -1min );
+
   is.clear();
   is.str("328 00");
   is >> parse("%3C %y", y); // 328 is out of range for %C (PR libstdc++/111162)
-- 
2.41.0