Change -v so that variences in units of days or less are sensitive to

DST.  Explain in more detail what date -v does when mixed with DST.

Previous code suggested broken by: wollman

1 files changed, 52 insertions, 64 deletions

diff --git a/bin/date/vary.c b/bin/date/vary.c
index 9063d38..4e46d1b2 100644
--- a/bin/date/vary.c
+++ b/bin/date/vary.c
@@ -53,25 +53,16 @@ static struct trans trans_wday[] = {
 };
 
 static char digits[] = "0123456789";
-static int adjhour(struct tm *, char, int);
+static int adjhour(struct tm *, char, int, int);
 
 static int
 domktime(struct tm *t, char type)
 {
-  int ret;
-
-  /*
-   * Don't let mktime have a specific tm_isdst value.  If we do,
-   * it gets confused when we ``vary'' in and out of Summer time
-   */
-  t->tm_isdst = -1;
-  if ((ret = mktime(t)) == -1 && t->tm_year > 68 && t->tm_year < 138)
-    /*
-     * If mktime() fails, adjust by an hour.  If we're actually
-     * bridging a savings of several hours, we'll recurse several
-     * times.
-     */
-    ret = adjhour(t, type == '-' ? type : '+', 1);
+  time_t ret;
+
+  while ((ret = mktime(t)) == -1 && t->tm_year > 68 && t->tm_year < 138)
+    /* While mktime() fails, adjust by an hour */
+    adjhour(t, type == '-' ? type : '+', 1, 0);
 
   return ret;
 }
@@ -134,7 +125,7 @@ daysinmonth(const struct tm *t)
 
 
 static int
-adjyear(struct tm *t, char type, int val)
+adjyear(struct tm *t, char type, int val, int mk)
 {
   switch (type) {
     case '+':
@@ -151,11 +142,11 @@ adjyear(struct tm *t, char type, int val)
         t->tm_year -= 1900;             /* struct tm holds years since 1900 */
       break;
   }
-  return domktime(t, type) != -1;
+  return !mk || domktime(t, type) != -1;
 }
 
 static int
-adjmon(struct tm *t, char type, int val, int istext)
+adjmon(struct tm *t, char type, int val, int istext, int mk)
 {
   if (val < 0)
     return 0;
@@ -169,7 +160,7 @@ adjmon(struct tm *t, char type, int val, int istext)
           val -= t->tm_mon + 1;		/* later this year */
       }
       if (val) {
-        if (!adjyear(t, '+', (t->tm_mon + val) / 12))
+        if (!adjyear(t, '+', (t->tm_mon + val) / 12, 0))
           return 0;
         val %= 12;
         t->tm_mon += val;
@@ -186,11 +177,11 @@ adjmon(struct tm *t, char type, int val, int istext)
           val = t->tm_mon - val + 1;	/* early this year */
       }
       if (val) {
-        if (!adjyear(t, '-', val / 12))
+        if (!adjyear(t, '-', val / 12, 0))
           return 0;
         val %= 12;
         if (val > t->tm_mon) {
-          if (!adjyear(t, '-', 1))
+          if (!adjyear(t, '-', 1, 0))
             return 0;
           val -= 12;
         }
@@ -204,11 +195,11 @@ adjmon(struct tm *t, char type, int val, int istext)
       t->tm_mon = --val;
   }
 
-  return domktime(t, type) != -1;
+  return !mk || domktime(t, type) != -1;
 }
 
 static int
-adjday(struct tm *t, char type, int val)
+adjday(struct tm *t, char type, int val, int mk)
 {
   int mdays;
 
@@ -219,7 +210,7 @@ adjday(struct tm *t, char type, int val)
         if (val > mdays - t->tm_mday) {
           val -= mdays - t->tm_mday + 1;
           t->tm_mday = 1;
-          if (!adjmon(t, '+', 1, 0))
+          if (!adjmon(t, '+', 1, 0, 0))
             return 0;
         } else {
           t->tm_mday += val;
@@ -232,7 +223,7 @@ adjday(struct tm *t, char type, int val)
         if (val >= t->tm_mday) {
           val -= t->tm_mday;
           t->tm_mday = 1;
-          if (!adjmon(t, '-', 1, 0))
+          if (!adjmon(t, '-', 1, 0, 0))
             return 0;
           t->tm_mday = daysinmonth(t);
         } else {
@@ -248,11 +239,11 @@ adjday(struct tm *t, char type, int val)
       break;
   }
 
-  return domktime(t, type) != -1;
+  return !mk || domktime(t, type) != -1;
 }
 
 static int
-adjwday(struct tm *t, char type, int val, int istext)
+adjwday(struct tm *t, char type, int val, int istext, int mk)
 {
   if (val < 0)
     return 0;
@@ -266,7 +257,7 @@ adjwday(struct tm *t, char type, int val, int istext)
           val -= t->tm_wday;           /* later this week */
       else
         val *= 7;                      /* "-v+5w" == "5 weeks in the future" */
-      return !val || adjday(t, '+', val);
+      return !val || adjday(t, '+', val, 0);
     case '-':
       if (istext) {
         if (val > t->tm_wday)
@@ -275,31 +266,21 @@ adjwday(struct tm *t, char type, int val, int istext)
           val = t->tm_wday - val;      /* early this week */
       } else
         val *= 7;                      /* "-v-5w" == "5 weeks ago" */
-      return !val || adjday(t, '-', val);
+      return !val || adjday(t, '-', val, 0);
     default:
       if (val < t->tm_wday)
-        return adjday(t, '-', t->tm_wday - val);
+        return adjday(t, '-', t->tm_wday - val, 0);
       else if (val > 6)
         return 0;
       else if (val > t->tm_wday)
-        return adjday(t, '+', val - t->tm_wday);
+        return adjday(t, '+', val - t->tm_wday, 0);
   }
   return 1;
 }
 
 static int
-adjhour(struct tm *t, char type, int val)
+adjhour(struct tm *t, char type, int val, int mk)
 {
-  /*
-   * We've got to be careful here in case
-   *   domktime() calls
-   *   adjhour() calls
-   *   adjday() calls
-   *   domktime() calls
-   *   adjhour() and recurses forever.  It's vital that we've adjusted our
-   *   number of hours before calling adjday().
-   */
-
   if (val < 0)
     return 0;
 
@@ -312,7 +293,7 @@ adjhour(struct tm *t, char type, int val)
         val %= 24;
         t->tm_hour += val;
         t->tm_hour %= 24;
-        if (!adjday(t, '+', days))
+        if (!adjday(t, '+', days, 0))
           return 0;
       }
       break;
@@ -328,7 +309,7 @@ adjhour(struct tm *t, char type, int val)
           val -= 24;
         }
         t->tm_hour -= val;
-        if (!adjday(t, '-', val / 24))
+        if (!adjday(t, '-', days, 0))
           return 0;
       }
       break;
@@ -339,11 +320,11 @@ adjhour(struct tm *t, char type, int val)
       t->tm_hour = val;
   }
 
-  return domktime(t, type) != -1;
+  return !mk || domktime(t, type) != -1;
 }
 
 static int
-adjmin(struct tm *t, char type, int val)
+adjmin(struct tm *t, char type, int val, int mk)
 {
   if (val < 0)
     return 0;
@@ -351,7 +332,7 @@ adjmin(struct tm *t, char type, int val)
   switch (type) {
     case '+':
       if (val) {
-        if (!adjhour(t, '+', (t->tm_min + val) / 60))
+        if (!adjhour(t, '+', (t->tm_min + val) / 60, 0))
           return 0;
         val %= 60;
         t->tm_min += val;
@@ -362,11 +343,11 @@ adjmin(struct tm *t, char type, int val)
 
     case '-':
       if (val) {
-        if (!adjhour(t, '-', val / 60))
+        if (!adjhour(t, '-', val / 60, 0))
           return 0;
         val %= 60;
         if (val > t->tm_min) {
-          if (!adjhour(t, '-', 1))
+          if (!adjhour(t, '-', 1, 0))
             return 0;
           val -= 60;
         }
@@ -380,11 +361,11 @@ adjmin(struct tm *t, char type, int val)
       t->tm_min = val;
   }
 
-  return domktime(t, type) != -1;
+  return !mk || domktime(t, type) != -1;
 }
 
 static int
-adjsec(struct tm *t, char type, int val)
+adjsec(struct tm *t, char type, int val, int mk)
 {
   if (val < 0)
     return 0;
@@ -392,7 +373,7 @@ adjsec(struct tm *t, char type, int val)
   switch (type) {
     case '+':
       if (val) {
-        if (!adjmin(t, '+', (t->tm_sec + val) / 60))
+        if (!adjmin(t, '+', (t->tm_sec + val) / 60, 0))
           return 0;
         val %= 60;
         t->tm_sec += val;
@@ -403,11 +384,11 @@ adjsec(struct tm *t, char type, int val)
 
     case '-':
       if (val) {
-        if (!adjmin(t, '-', val / 60))
+        if (!adjmin(t, '-', val / 60, 0))
           return 0;
         val %= 60;
         if (val > t->tm_sec) {
-          if (!adjmin(t, '-', 1))
+          if (!adjmin(t, '-', 1, 0))
             return 0;
           val -= 60;
         }
@@ -421,7 +402,7 @@ adjsec(struct tm *t, char type, int val)
       t->tm_sec = val;
   }
 
-  return domktime(t, type) != -1;
+  return !mk || domktime(t, type) != -1;
 }
 
 const struct vary *
@@ -444,15 +425,18 @@ vary_apply(const struct vary *v, struct tm *t)
     if (len < 2)
       return v;
 
+    if (type == '\0')
+      t->tm_isdst = -1;
+
     if (strspn(arg, digits) != len-1) {
       val = trans(trans_wday, arg);
       if (val != -1) {
-          if (!adjwday(t, type, val, 1))
+          if (!adjwday(t, type, val, 1, 1))
             return v;
       } else {
         val = trans(trans_mon, arg);
         if (val != -1) {
-          if (!adjmon(t, type, val, 1))
+          if (!adjmon(t, type, val, 1, 1))
             return v;
         } else
           return v;
@@ -463,31 +447,35 @@ vary_apply(const struct vary *v, struct tm *t)
       
       switch (which) {
         case 'S':
-          if (!adjsec(t, type, val))
+          if (!adjsec(t, type, val, 1))
             return v;
           break;
         case 'M':
-          if (!adjmin(t, type, val))
+          if (!adjmin(t, type, val, 1))
             return v;
           break;
         case 'H':
-          if (!adjhour(t, type, val))
+          if (!adjhour(t, type, val, 1))
             return v;
           break;
         case 'd':
-          if (!adjday(t, type, val))
+          t->tm_isdst = -1;
+          if (!adjday(t, type, val, 1))
             return v;
           break;
         case 'w':
-          if (!adjwday(t, type, val, 0))
+          t->tm_isdst = -1;
+          if (!adjwday(t, type, val, 0, 1))
             return v;
           break;
         case 'm':
-          if (!adjmon(t, type, val, 0))
+          t->tm_isdst = -1;
+          if (!adjmon(t, type, val, 0, 1))
             return v;
           break;
         case 'y':
-          if (!adjyear(t, type, val))
+          t->tm_isdst = -1;
+          if (!adjyear(t, type, val, 1))
             return v;
           break;
         default: