[newlib-cygwin/main] Cygwin: strptime: fix am/pm handling

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=585855eef8639e6066bb7c12753deed33a6018b4

commit 585855eef8639e6066bb7c12753deed33a6018b4
Author:     Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Wed Feb 21 19:54:20 2024 +0100
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Wed Feb 21 19:54:20 2024 +0100

    Cygwin: strptime: fix am/pm handling
    
    The %p format specifier is handled immediately.  It requires
    that tm_hour is already set.  This falls flat in case the am/pm
    marker preceeds the time specification.  Locales with am/pm
    marker preceeding time spec by default exist (e. g. ko_KR).
    
    Also, the code expects that tm_hour might be set to an invalid
    value because the %p specifier is used in conjunction with %H.
    But this usage is invalid in itself and now catched as error
    condition after commit 343a2a558153 ("Cygwin: strptime: make
    sure to fail on invalid input digits").
    
    Change the %H/%I/%p handling according to GLibC, i. e.
    
    - fix tm_hour for pm only if the time value has been specified
      as 12 hour time %I, and
    
    - perform the fixup only after the entire input has been scanned.
      This decouples the fixup from the %p position relativ to %I.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/libc/strptime.cc | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/libc/strptime.cc b/winsup/cygwin/libc/strptime.cc
index 353b8008a1c9..dc6771fe5e23 100644
--- a/winsup/cygwin/libc/strptime.cc
+++ b/winsup/cygwin/libc/strptime.cc
@@ -335,6 +335,8 @@ __strptime(const char *buf, const char *fmt, struct tm *tm,
 	const char *new_fmt;
 	uint ulim;
 	int ymd = 0;
+	bool got_I = false;
+	bool got_pm = false;
 
 	bp = (const unsigned char *)buf;
 	const struct lc_time_T *_CurrentTimeLocale = __get_time_locale (locale);
@@ -537,6 +539,7 @@ literal:
 		case 'H':
 			LEGAL_ALT(ALT_O);
 			bp = conv_num(bp, &tm->tm_hour, 0, 23, ALT_DIGITS);
+			got_I = false;
 			continue;
 
 		case 'l':	/* The hour (12-hour clock representation). */
@@ -547,6 +550,7 @@ literal:
 			bp = conv_num(bp, &tm->tm_hour, 1, 12, ALT_DIGITS);
 			if (tm->tm_hour == 12)
 				tm->tm_hour = 0;
+			got_I = true;
 			continue;
 
 		case 'j':	/* The day of year. */
@@ -573,9 +577,7 @@ literal:
 		case 'p':	/* The locale's equivalent of AM/PM. */
 			bp = find_string(bp, &i, _ctloc(am_pm), NULL, 2,
 					 locale);
-			if (tm->tm_hour > 11)
-				return NULL;
-			tm->tm_hour += i * 12;
+			got_pm = (i == 1);
 			LEGAL_ALT(0);
 			continue;
 
@@ -751,8 +753,12 @@ literal:
 		default:	/* Unknown/unsupported conversion. */
 			return NULL;
 		}
+
 	}
 
+	if (got_I && got_pm)
+	  tm->tm_hour += 12;
+
 	if (bp && (era || got_eoff))
 	  {
 	    /* Default to current era. */