Merge branch 'fix-mktime' into 'master'

fix: mktime: stop using tm_gmtoff, use system timezone per POSIX

See merge request redox-os/relibc!1435

src/header/time/mod.rs

@@ -23,7 +23,7 @@ use crate::{
 };
 use alloc::collections::BTreeSet;
 use chrono::{
-    DateTime, Datelike, FixedOffset, NaiveDate, NaiveDateTime, Offset, TimeZone, Timelike, Utc,
+    DateTime, Datelike, NaiveDate, NaiveDateTime, Offset, TimeZone, Timelike, Utc,
     offset::MappedLocalTime,
 };
 use chrono_tz::{OffsetComponents, OffsetName, Tz};
@@ -451,19 +451,22 @@ pub unsafe extern "C" fn mktime(timeptr: *mut tm) -> time_t {
         }
     };
 
-    let offset = get_offset(unsafe { (*timeptr).tm_gmtoff }).unwrap();
     let tz = time_zone();
-    // Create DateTime<FixedOffset>
-    let datetime = match offset.from_local_datetime(&naive_local) {
+    let isdst = unsafe { (*timeptr).tm_isdst };
+    let tz_datetime = match tz.from_local_datetime(&naive_local) {
         MappedLocalTime::Single(datetime) => datetime,
-        _ => {
+        MappedLocalTime::Ambiguous(early, late) => {
+            if isdst > 0 {
+                early
+            } else {
+                late
+            }
+        }
+        MappedLocalTime::None => {
             platform::ERRNO.set(EOVERFLOW);
             return -1;
         }
     };
-
-    // Convert to UTC and get timestamp
-    let tz_datetime = datetime.with_timezone(&tz);
     let timestamp = tz_datetime.timestamp();
 
     unsafe { ptr::write(timeptr, datetime_to_tm(&tz_datetime)) };
@@ -859,15 +862,6 @@ unsafe fn set_timezone(
     }
 }
 
-#[inline(always)]
-pub const fn get_offset(off: c_long) -> Option<FixedOffset> {
-    if off < 0 {
-        FixedOffset::west_opt(off as _)
-    } else {
-        FixedOffset::east_opt(off as _)
-    }
-}
-
 const fn blank_tm() -> tm {
     tm {
         tm_year: 0,

tests/expected/time/mktime.stdout

@@ -4,3 +4,4 @@
 -500 = -500
 0 = 0
 1531454950 = 1531454950
+gmtoff_ignored = 1

tests/time/mktime.c

@@ -57,4 +57,16 @@ int main(void) {
             printf("Comparison %ld == %ld failed. Time: %s", input, output, asctime(time));
         }
     }
+
+    // mktime must not panic on out-of-range tm_gmtoff
+    {
+        struct tm tg = { 0 };
+        tg.tm_year = 124;
+        tg.tm_mon = 0;
+        tg.tm_mday = 1;
+        tg.tm_hour = 12;
+        tg.tm_gmtoff = 100000;
+        time_t result = mktime(&tg);
+        printf("gmtoff_ignored = %d\n", result != (time_t)-1);
+    }
 }