[newlib-cygwin/main] Cygwin: strptime: make sure to fail on invalid input digits

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=343a2a558153318b37de5fa6afc2d656739f0eed

commit 343a2a558153318b37de5fa6afc2d656739f0eed
Author:     Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Wed Feb 21 19:39:37 2024 +0100
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Wed Feb 21 19:39:37 2024 +0100

    Cygwin: strptime: make sure to fail on invalid input digits
    
    conv_num returns NULL if the input is invalid, e. g., the
    numbers are out of range.  However, the code fails to test
    this in a lot of places.
    
    Rather than adding checks all over the place, rename conv_num
    to __conv_num and create a wrapper macro conv_num to perform
    the task of error checking.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/libc/strptime.cc | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/libc/strptime.cc b/winsup/cygwin/libc/strptime.cc
index dc557231012d..353b8008a1c9 100644
--- a/winsup/cygwin/libc/strptime.cc
+++ b/winsup/cygwin/libc/strptime.cc
@@ -301,10 +301,19 @@ first_day (int year)
   return ret;
 }
 
-/* This simplifies the calls to conv_num enormously. */
+/* This simplifies the calls to __conv_num enormously. */
 #define ALT_DIGITS	((alt_format & ALT_O) ? *alt_digits : NULL)
 
-static const unsigned char *conv_num(const unsigned char *, int *, uint, uint,
+#define conv_num(_b,_d,_l,_u,_a)	\
+		({							\
+		  const unsigned char *_ret;				\
+		  _ret = __conv_num((_b),(_d),(_l),(_u),(_a));		\
+		  if (!_ret)						\
+		    return NULL;					\
+		  _ret;							\
+		})
+
+static const unsigned char *__conv_num(const unsigned char *, int *, uint, uint,
 				     alt_digits_t *);
 static const unsigned char *find_string(const unsigned char *, int *,
 					const char * const *,
@@ -842,7 +851,7 @@ strptime (const char *__restrict buf, const char *__restrict fmt,
 }
 
 static const unsigned char *
-conv_num(const unsigned char *buf, int *dest, uint llim, uint ulim,
+__conv_num(const unsigned char *buf, int *dest, uint llim, uint ulim,
 	 alt_digits_t *alt_digits)
 {
 	uint result = 0;