BUG: Attempt Y2038 fix, and restrict local timezone parsing to 1970 and later, because of Win32

On MS Windows, dates earlier than 1970 cause mktime to error. This patch
also applies to parsing the same Y2038 hack that was done for printing.

1 files changed, 77 insertions, 37 deletions

diff --git a/numpy/core/src/multiarray/datetime_strings.c b/numpy/core/src/multiarray/datetime_strings.c
index a3964c000..97d170230 100644
--- a/numpy/core/src/multiarray/datetime_strings.c
+++ b/numpy/core/src/multiarray/datetime_strings.c
@@ -185,6 +185,81 @@ convert_datetimestruct_utc_to_local(npy_datetimestruct *out_dts_local,
 }
 
 /*
+ * Converts a datetimestruct in local time to a datetimestruct in UTC.
+ *
+ * Returns 0 on success, -1 on failure.
+ */
+static int
+convert_datetimestruct_local_to_utc(npy_datetimestruct *out_dts_utc,
+                const npy_datetimestruct *dts_local)
+{
+    npy_int64 year_correction = 0;
+
+    /* Make a copy of the input 'dts' to modify */
+    *out_dts_utc = *dts_local;
+
+    /* HACK: Use a year < 2038 for later years for small time_t */
+    if (sizeof(NPY_TIME_T) == 4 && out_dts_utc->year >= 2038) {
+        if (is_leapyear(out_dts_utc->year)) {
+            /* 2036 is a leap year */
+            year_correction = out_dts_utc->year - 2036;
+            out_dts_utc->year -= year_correction;
+        }
+        else {
+            /* 2037 is not a leap year */
+            year_correction = out_dts_utc->year - 2037;
+            out_dts_utc->year -= year_correction;
+        }
+    }
+
+    /*
+     * ISO 8601 states to treat date-times without a timezone offset
+     * or 'Z' for UTC as local time. The C standard libary functions
+     * mktime and gmtime allow us to do this conversion.
+     *
+     * Only do this timezone adjustment for recent and future years.
+     * In this case, "recent" is defined to be 1970 and later, because
+     * on MS Windows, mktime raises an error when given an earlier date.
+     */
+    if (out_dts_utc->year >= 1970) {
+        NPY_TIME_T rawtime = 0;
+        struct tm tm_;
+
+        tm_.tm_sec = out_dts_utc->sec;
+        tm_.tm_min = out_dts_utc->min;
+        tm_.tm_hour = out_dts_utc->hour;
+        tm_.tm_mday = out_dts_utc->day;
+        tm_.tm_mon = out_dts_utc->month - 1;
+        tm_.tm_year = out_dts_utc->year - 1900;
+        tm_.tm_isdst = -1;
+
+        /* mktime converts a local 'struct tm' into a time_t */
+        rawtime = mktime(&tm_);
+        if (rawtime == -1) {
+            PyErr_SetString(PyExc_OSError, "Failed to use mktime to "
+                                        "convert local time to UTC");
+            return -1;
+        }
+
+        /* gmtime converts a 'time_t' into a UTC 'struct tm' */
+        if (get_gmtime(&rawtime, &tm_) < 0) {
+            return -1;
+        }
+        out_dts_utc->sec = tm_.tm_sec;
+        out_dts_utc->min = tm_.tm_min;
+        out_dts_utc->hour = tm_.tm_hour;
+        out_dts_utc->day = tm_.tm_mday;
+        out_dts_utc->month = tm_.tm_mon + 1;
+        out_dts_utc->year = tm_.tm_year + 1900;
+    }
+
+    /* Reapply the year 2038 year correction HACK */
+    out_dts_utc->year += year_correction;
+
+    return 0;
+}
+
+/*
  * Parses (almost) standard ISO 8601 date strings. The differences are:
  *
  * + The date "20100312" is parsed as the year 20100312, not as
@@ -653,43 +728,8 @@ parse_iso_8601_datetime(char *str, int len,
 
 parse_timezone:
     if (sublen == 0) {
-        /*
-         * ISO 8601 states to treat date-times without a timezone offset
-         * or 'Z' for UTC as local time. The C standard libary functions
-         * mktime and gmtime allow us to do this conversion.
-         *
-         * Only do this timezone adjustment for recent and future years.
-         */
-        if (out->year > 1900 && out->year < 10000) {
-            NPY_TIME_T rawtime = 0;
-            struct tm tm_;
-
-            tm_.tm_sec = out->sec;
-            tm_.tm_min = out->min;
-            tm_.tm_hour = out->hour;
-            tm_.tm_mday = out->day;
-            tm_.tm_mon = out->month - 1;
-            tm_.tm_year = out->year - 1900;
-            tm_.tm_isdst = -1;
-
-            /* mktime converts a local 'struct tm' into a time_t */
-            rawtime = mktime(&tm_);
-            if (rawtime == -1) {
-                PyErr_SetString(PyExc_OSError, "Failed to use mktime to "
-                                            "convert local time to UTC");
-                goto error;
-            }
-
-            /* gmtime converts a 'time_t' into a UTC 'struct tm' */
-            if (get_gmtime(&rawtime, &tm_) < 0) {
-                goto error;
-            }
-            out->sec = tm_.tm_sec;
-            out->min = tm_.tm_min;
-            out->hour = tm_.tm_hour;
-            out->day = tm_.tm_mday;
-            out->month = tm_.tm_mon + 1;
-            out->year = tm_.tm_year + 1900;
+        if (convert_datetimestruct_local_to_utc(out, out) < 0) {
+            goto error;
         }
 
         /* Since neither "Z" nor a time-zone was specified, it's local */