From a69f4fb067ec22b95741e37efe355fb1106fefd2 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Mon, 7 Jul 2025 08:44:05 -0400
Subject: prelude: Move countof() here from bfs.h

countof() will likely be in the C2Y standard.

Link: https://www.open-std.org/JTC1/SC22/WG14/www/docs/n3469.htm
Link: https://thephd.dev/c2y-hitting-the-ground-running
---
 src/bfs.h     | 5 -----
 src/prelude.h | 9 +++++++++
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/bfs.h b/src/bfs.h
index 70a7282..ab96bf5 100644
--- a/src/bfs.h
+++ b/src/bfs.h
@@ -58,11 +58,6 @@ extern const char bfs_ldlibs[];
 
 // Fundamental utilities
 
-/**
- * Get the length of an array.
- */
-#define countof(...) (sizeof(__VA_ARGS__) / sizeof(0[__VA_ARGS__]))
-
 /**
  * False sharing/destructive interference/largest cache line size.
  */
diff --git a/src/prelude.h b/src/prelude.h
index 3b1c4e5..1663af6 100644
--- a/src/prelude.h
+++ b/src/prelude.h
@@ -88,6 +88,15 @@
 
 #endif // !C23
 
+// Future C standard backports
+
+/**
+ * Get the length of an array.
+ *
+ * https://www.open-std.org/JTC1/SC22/WG14/www/docs/n3469.htm
+ */
+#define countof(...) (sizeof(__VA_ARGS__) / sizeof(0[__VA_ARGS__]))
+
 // Feature detection
 
 // https://clang.llvm.org/docs/LanguageExtensions.html#has-attribute
-- 
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