From a97980ef596c8093f64515fe4a8a2f13351cedc5 Mon Sep 17 00:00:00 2001
From: Neil <neil@sdf.org>
Date: Thu, 31 Mar 2022 23:09:02 -0700
Subject: [PATCH] 2011 C anonymous unions

---
 src/interpret.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/interpret.c b/src/interpret.c
index c0a7137..036ac97 100644
--- a/src/interpret.c
+++ b/src/interpret.c
@@ -1,3 +1,5 @@
+/** @std GNU C11 */
+
 #include "lex.h"
 #include <unistd.h> /* chdir (POSIX) */
 #include <sys/types.h> /* mode_t (POSIX) */
@@ -6,6 +8,7 @@
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h>
 
 #if INT_MAX >= 100000000000
 #error int_to_string requires truncation on this compiler.
@@ -64,11 +67,16 @@ static int leap(int y) {
 	if(!(y % 4)) return 1;
 	return 0;
 }
-/** Not defined for some implementations. */
-struct date32 { unsigned year : 23, month : 4, day : 5; };
+/** Not defined for some implementations. (I think the standard also doesn't
+ say which order they should be, that's a problem.) */
+union date32 {
+	uint32_t i32;
+	struct { unsigned year : 23, month : 4, day : 5; };
+	/* This is unsetting. Obv. it should be `struct anonymous {};`. */
+};
 /** Convert or narrower type or return zero. */
-static struct date32 date_to_32(const int y, const int m, const int d) {
-	struct date32 d32 = { 0, 0, 0 };
+static union date32 date_to_32(const int y, const int m, const int d) {
+	union date32 d32 = { 0 };
 	/* Leap year calculations only work at y>=1 and Gregorian Calendar and max
 	 23 bits. */
 	if(y < 1582 || y > 8388607 || m < 1 || m > 12 || d < 1 || d > 31)
@@ -84,7 +92,7 @@ static struct date32 date_to_32(const int y, const int m, const int d) {
 }
 
 /** Tomohiko Sakamoto comp.lang.c 1993-04-10. */
-static unsigned weekday(struct date32 d) {
+static unsigned weekday(union date32 d) {
 	d.year -= d.month < 3;
 	return (d.year + d.year / 4 - d.year / 100 + d.year / 400
 		+ "-bed=pen+mad."[d.month] + d.day) % 7;
@@ -94,7 +102,7 @@ static unsigned weekday(struct date32 d) {
 #define ARRAY_TYPE struct lex
 #include "array.h"
 struct page {
-	struct date32 date;
+	union date32 date;
 	struct char_array entry;
 	struct lex_array lexx;
 };
@@ -127,6 +135,7 @@ int main(int argc, char **argv) {
 		*p = year;
 	}
 	closedir(dir), dir = 0;
+	/* Sort the years for sensible ordering of parsing. */
 	qsort(years.data, years.size, sizeof *years.data, &void_int_cmp);
 	fprintf(stderr, "Files in %s: %s.\n", argv[1], int_array_to_string(&years));