unalf: warn about all-zero ALF header dates.

6 files changed, 23 insertions, 5 deletions

diff --git a/src/alf.1 b/src/alf.1
index d645742..371f903 100644
--- a/src/alf.1
+++ b/src/alf.1
@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "ALF" 1 "2025-12-01" "0.3.0" "Urchlay's Atari 8-bit Tools"
+.TH "ALF" 1 "2025-12-02" "0.3.0" "Urchlay's Atari 8-bit Tools"
 .SH NAME
 alf \- create Atari 8-bit ALF archives
 .\" RST source for alf(1) man page. Convert with:
@@ -108,7 +108,8 @@ Use UTC for timestamps (default is local timezone).
 .INDENT 0.0
 .TP
 .B \fB\-tz\fP
-Use zero for timestamps (0 ??? 80  12:00a).
+Use zero for timestamps. \fBunalf\fP will display \fI<none>\fP for the
+date and midnight for the time.
 .UNINDENT
 .\" use zero timestamps.
 .
diff --git a/src/alf.rst b/src/alf.rst
index 75869ca..267f993 100644
--- a/src/alf.rst
+++ b/src/alf.rst
@@ -84,7 +84,8 @@ OPTIONS
 .. use UTC timestamps.
 
 **-tz**
-  Use zero for timestamps (0 ??? 80  12:00a).
+  Use zero for timestamps. **unalf** will display *<none>* for the
+  date and midnight for the time.
 
 .. use zero timestamps.
 
diff --git a/src/crunch.c b/src/crunch.c
index ada46e8..5f21223 100644
--- a/src/crunch.c
+++ b/src/crunch.c
@@ -121,6 +121,7 @@ void inc_output_len(void) {
 		fprintf(stderr, "%s: fatal: compressed file would be >16MB.\n", self);
 		exit(1);
 	}
+	output_buf[output_len] = 0;
 }
 
 void append_bit(int bit) {
diff --git a/src/extract.c b/src/extract.c
index b14b321..98523db 100644
--- a/src/extract.c
+++ b/src/extract.c
@@ -51,7 +51,10 @@ void set_datetime() {
 	t = dpeek(alf_hdr_time0);
 
 	/* don't set the date/time at all, if it's zero */
-	if(!t) return;
+	if(!t) {
+		fprintf(stderr, "%s: warning: date/time for %s is null, using current date/time\n", self, out_filename);
+		return;
+	}
 
 	d = dpeek(alf_hdr_date0);
 
diff --git a/src/unalf.1 b/src/unalf.1
index c1683a4..f7d4ff3 100644
--- a/src/unalf.1
+++ b/src/unalf.1
@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "UNALF" 1 "2025-12-01" "0.3.0" "Urchlay's Atari 8-bit Tools"
+.TH "UNALF" 1 "2025-12-02" "0.3.0" "Urchlay's Atari 8-bit Tools"
 .SH NAME
 unalf \- extract Atari 8-bit ALF archives
 .\" RST source for unalf(1) man page. Convert with:
@@ -345,6 +345,12 @@ your \fIALF\fP file actually contains another \fIALF\fP file, but that would
 be a pathological case. Most likely, you\(aqre trying to extract multiple
 \fIALF\fP files with one command, which doesn\(aqt work. Use one \fBunalf\fP
 command per file.
+.TP
+.B \fBdate/time for <file> is null, using current date/time\fP
+The date stored in the \fIALF\fP header for this file is all zeroes, which
+is an invalid date. \fBunalf \-v\fP shows this as \fI<none>\fP\&. The
+date on the extracted file can\(aqt be set, so it\(aqll have the current
+date and time instead.
 .UNINDENT
 .SH NOTES
 .sp
diff --git a/src/unalf.rst b/src/unalf.rst
index 3550a3b..146e056 100644
--- a/src/unalf.rst
+++ b/src/unalf.rst
@@ -300,6 +300,12 @@ Warnings
   *ALF* files with one command, which doesn't work. Use one **unalf**
   command per file.
 
+**date/time for <file> is null, using current date/time**
+  The date stored in the *ALF* header for this file is all zeroes, which
+  is an invalid date. **unalf -v** shows this as *<none>*. The
+  date on the extracted file can't be set, so it'll have the current
+  date and time instead.
+
 NOTES
 =====