[tz] [PROPOSED PATCH] Fix zdump problem with abbrevs like '-05'

[Paul Eggert]

* zdump.c (is_digit): New macro, copied from private.h.
(abbrok): Use it.  Allow abbreviations that (when quoted) conform
to POSIX.1-2001 or later.
* NEWS: Document this.
---
 NEWS    |  3 ++-
 zdump.c | 28 +++++++++++-----------------
 2 files changed, 13 insertions(+), 18 deletions(-)

diff --git a/NEWS b/NEWS
index 498e77b..101a1e5 100644
--- a/NEWS
+++ b/NEWS
@@ -21,7 +21,8 @@ Unreleased, experimental changes
 
   Changes affecting code
 
-    zic no longer warns about valid time zone abbreviations like '-05'.
+    zdump and zic no longer warn about valid time zone abbreviations
+    like '-05'.
 
 
 Release 2015e - 2015-06-13 10:56:02 -0700
diff --git a/zdump.c b/zdump.c
index adb806c..64ff6ce 100644
--- a/zdump.c
+++ b/zdump.c
@@ -269,6 +269,9 @@ static void show(timezone_t, char *, time_t, bool);
 static const char *tformat(void);
 static time_t yeartot(intmax_t) ATTRIBUTE_PURE;
 
+/* Unlike <ctype.h>'s isdigit, this also works if c < 0 | c > UCHAR_MAX. */
+#define is_digit(c) ((unsigned)(c) - '0' <= 9)
+
 /* Is A an alphabetic character in the C locale?  */
 static bool
 is_alpha(char a)
@@ -485,25 +488,16 @@ abbrok(const char *const abbrp, const char *const zone)
 	if (warned)
 		return;
 	cp = abbrp;
-	wp = NULL;
-	while (is_alpha(*cp))
+	while (is_alpha(*cp) || is_digit(*cp) || *cp == '-' || *cp == '+')
 		++cp;
-	if (cp - abbrp == 0)
-		wp = _("lacks alphabetic at start");
-	else if (cp - abbrp < 3)
-		wp = _("has fewer than 3 alphabetics");
+	if (cp - abbrp < 3)
+	  wp = _("has fewer than 3 characters");
 	else if (cp - abbrp > 6)
-		wp = _("has more than 6 alphabetics");
-	if (wp == NULL && (*cp == '+' || *cp == '-')) {
-		++cp;
-		if ('0' <= *cp && *cp <= '9')
-			if (*cp++ == '1' && '0' <= *cp && *cp <= '4')
-				cp++;
-		if (*cp != '\0')
-			wp = _("differs from POSIX standard");
-	}
-	if (wp == NULL)
-		return;
+	  wp = _("has more than 6 characters");
+	else if (*cp)
+	  wp = _("has characters other than ASCII alphanumerics, '-' or '+'");
+	else
+	  return;
 	fflush(stdout);
 	fprintf(stderr,
 		_("%s: warning: zone \"%s\" abbreviation \"%s\" %s\n"),
-- 
2.1.0