From 84ecc332421e4749ec5a35bddc656dd854ebe16e Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Sat, 19 Mar 2022 21:25:10 -0400
Subject: datetime: Sanity check parsing results

Previously, "0000 1970-01-01" was parsed as 00:00:19 70-01-01.

Fixes:

    not ok 614 - 0000 1970-01-01
    FAIL: tests/parse.sh 614 - 0000 1970-01-01
    #  Failed test '0000 1970-01-01'
    #          got: '-59958143981'
    #     expected: '0'
    ok 615 - 1970/01/01 0000
    PASS: tests/parse.sh 615 - 1970/01/01 0000
    not ok 616 - 0000 1970/01/01
    FAIL: tests/parse.sh 616 - 0000 1970/01/01
    #  Failed test '0000 1970/01/01'
    #          got: '-59958143981'
    #     expected: '0'
---
diff --git a/TODO b/TODO
index 65918f0..3be30d2 100644
--- a/TODO
+++ b/TODO
@@ -1,5 +1,4 @@
 spaces between specifiers in strptime() formats -- strftime()?
 test with other libc's (newlib? musl? fbsd? obsd?)
-formats beginning with HHMM are mis-parsed as years
 `./@ 7:00 PM` doesn't work with musl strptime()
 gettext?
diff --git a/src/datetime.c b/src/datetime.c
index 994d3fe..a3b4c58 100644
--- a/src/datetime.c
+++ b/src/datetime.c
@@ -192,6 +192,8 @@ datetime_parse(struct tm *now_tm, const char *input, time_t *arg_sec)
 	size_t     t;
 	char      *end;
 	struct tm  arg_tm;
+	time_t     sec;
+	bool       got;
 
 	date_fmt_len = strlen(DATETIME_DATE_FMTS_[0]);
 	time_fmt_len = strlen(DATETIME_TIME_FMTS_[0]);
@@ -202,14 +204,20 @@ datetime_parse(struct tm *now_tm, const char *input, time_t *arg_sec)
 		return -1;
 	}
 
+	sec = *arg_sec;  /* GCC is dumb. */
+	got = false;
 	for (t = 0; t < sizeof(DATETIME_TIME_FMTS_) /
 			sizeof(DATETIME_TIME_FMTS_[0]) ; ++t) {
 		_datetime_reset_tm(&arg_tm);
 		end = strptime(input, DATETIME_TIME_FMTS_[t], &arg_tm);
 		if (end != NULL && *end == '\0') {
-			free(fmt_buf);
 			_datetime_normalize(now_tm, &arg_tm, arg_sec);
-			return 0;
+			if (datetime_diff_epoch(*arg_sec) >= 0) {
+				free(fmt_buf);
+				return 0;
+			}
+			sec = *arg_sec;
+			got = true;
 		}
 	}
 	for (d = 0; d < sizeof(DATETIME_DATE_FMTS_) /
@@ -222,9 +230,13 @@ datetime_parse(struct tm *now_tm, const char *input, time_t *arg_sec)
 			_datetime_reset_tm(&arg_tm);
 			end = strptime(input, fmt_buf, &arg_tm);
 			if (end != NULL && *end == '\0') {
-				free(fmt_buf);
 				_datetime_normalize(now_tm, &arg_tm, arg_sec);
-				return 0;
+				if (datetime_diff_epoch(*arg_sec) >= 0) {
+					free(fmt_buf);
+					return 0;
+				}
+				sec = *arg_sec;
+				got = true;
 			}
 		}
 	}
@@ -238,9 +250,13 @@ datetime_parse(struct tm *now_tm, const char *input, time_t *arg_sec)
 			_datetime_reset_tm(&arg_tm);
 			end = strptime(input, fmt_buf, &arg_tm);
 			if (end != NULL && *end == '\0') {
-				free(fmt_buf);
 				_datetime_normalize(now_tm, &arg_tm, arg_sec);
-				return 0;
+				if (datetime_diff_epoch(*arg_sec) >= 0) {
+					free(fmt_buf);
+					return 0;
+				}
+				sec = *arg_sec;
+				got = true;
 			}
 		}
 	}
@@ -249,15 +265,25 @@ datetime_parse(struct tm *now_tm, const char *input, time_t *arg_sec)
 		_datetime_reset_tm(&arg_tm);
 		end = strptime(input, DATETIME_MISC_FMTS_[d], &arg_tm);
 		if (end != NULL && *end == '\0') {
-			free(fmt_buf);
 			_datetime_normalize(now_tm, &arg_tm, arg_sec);
-			return 0;
+			if (datetime_diff_epoch(*arg_sec) >= 0) {
+				free(fmt_buf);
+				return 0;
+			}
+			sec = *arg_sec;
+			got = true;
 		}
 	}
 
-	free(fmt_buf);
-	fputs("Unknown date format\n", stderr);
-	return -1;
+	if (got == true) {
+		*arg_sec = sec;
+		free(fmt_buf);
+		return 0;
+	} else {
+		fputs("Unknown date format\n", stderr);
+		free(fmt_buf);
+		return -1;
+	}
 }
 
 static void
--
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