simplify strftime and fix integer overflows

use a long long value so that even with offsets, values cannot
overflow. instead of using different format strings for different
numeric formats, simply use a per-format width and %0*lld for all of
them.

this width specifier is not for use with strftime field widths; that
will be a separate step in the caller.

diff --git a/src/time/strftime.c b/src/time/strftime.c
index 880e41a1314872fd32d76259a6e1633e0bba3a10..19ffdbca3729ee0899cffebc7e2df0a0f332c9a5 100644 (file)
--- a/src/time/strftime.c
+++ b/src/time/strftime.c
@@ -6,8 +6,6 @@
 #include <limits.h>
 #include "libc.h"
 
-// FIXME: integer overflows
-
 const char *__nl_langinfo_l(nl_item, locale_t);
 
 static int is_leap(int y)
@@ -49,8 +47,9 @@ size_t __strftime_l(char *restrict, size_t, const char *restrict, const struct t
 const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *tm, locale_t loc)
 {
        nl_item item;
-       int val;
+       long long val;
        const char *fmt;
+       int width = 2;
 
        switch (f) {
        case 'a':
@@ -70,55 +69,45 @@ const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *
                item = D_T_FMT;
                goto nl_strftime;
        case 'C':
-               val = (1900+tm->tm_year) / 100;
-               fmt = "%02d";
+               val = (1900LL+tm->tm_year) / 100;
                goto number;
        case 'd':
                val = tm->tm_mday;
-               fmt = "%02d";
                goto number;
        case 'D':
                fmt = "%m/%d/%y";
                goto recu_strftime;
        case 'e':
                val = tm->tm_mday;
-               fmt = "%2d";
                goto number;
        case 'F':
                fmt = "%Y-%m-%d";
                goto recu_strftime;
        case 'g':
        case 'G':
-               fmt = "%04d";
-               val = tm->tm_year + 1900;
+               val = tm->tm_year + 1900LL;
                if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
                else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
-               if (f=='g') {
-                       fmt = "%02d";
-                       val %= 100;
-               }
+               if (f=='g') val %= 100;
+               else width = 4;
                goto number;
        case 'H':
                val = tm->tm_hour;
-               fmt = "%02d";
                goto number;
        case 'I':
                val = tm->tm_hour;
                if (!val) val = 12;
                else if (val > 12) val -= 12;
-               fmt = "%02d";
                goto number;
        case 'j':
                val = tm->tm_yday+1;
-               fmt = "%03d";
+               width = 3;
                goto number;
        case 'm':
                val = tm->tm_mon+1;
-               fmt = "%02d";
                goto number;
        case 'M':
                val = tm->tm_min;
-               fmt = "%02d";
                goto number;
        case 'n':
                *l = 1;
@@ -134,7 +123,6 @@ const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *
                goto recu_strftime;
        case 'S':
                val = tm->tm_sec;
-               fmt = "%02d";
                goto number;
        case 't':
                *l = 1;
@@ -144,23 +132,20 @@ const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *
                goto recu_strftime;
        case 'u':
                val = tm->tm_wday ? tm->tm_wday : 7;
-               fmt = "%d";
+               width = 1;
                goto number;
        case 'U':
                val = (tm->tm_yday + 7 - tm->tm_wday) / 7;
-               fmt = "%02d";
                goto number;
        case 'W':
                val = (tm->tm_yday + 7 - (tm->tm_wday+6)%7) / 7;
-               fmt = "%02d";
                goto number;
        case 'V':
                val = week_num(tm);
-               fmt = "%02d";
                goto number;
        case 'w':
                val = tm->tm_wday;
-               fmt = "%d";
+               width = 1;
                goto number;
        case 'x':
                item = D_FMT;
@@ -170,11 +155,10 @@ const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *
                goto nl_strftime;
        case 'y':
                val = tm->tm_year % 100;
-               fmt = "%02d";
                goto number;
        case 'Y':
-               val = tm->tm_year + 1900;
-               fmt = "%04d";
+               val = tm->tm_year + 1900LL;
+               width = 4;
                goto number;
        case 'z':
                val = -tm->__tm_gmtoff;
@@ -190,7 +174,7 @@ const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *
                return 0;
        }
 number:
-       *l = snprintf(*s, sizeof *s, fmt, val);
+       *l = snprintf(*s, sizeof *s, "%0*lld", width, val);
        return *s;
 nl_strcat:
        fmt = __nl_langinfo_l(item, loc);