From 377b427491bcbf00e97fe02f69ef253e5ea3a53b Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Wed, 29 May 2024 11:51:10 -0400
Subject: bit: Use <stdbit.h> if it exists, even without -std=c23

glibc added an implementation in 2.39.
---
 src/bit.h     | 6 +++---
 src/prelude.h | 4 ++++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/bit.h b/src/bit.h
index 880ccd6..c494130 100644
--- a/src/bit.h
+++ b/src/bit.h
@@ -12,7 +12,7 @@
 #include <limits.h>
 #include <stdint.h>
 
-#if __STDC_VERSION__ >= C23
+#if BFS_HAS_STDBIT_H
 #  include <stdbit.h>
 #endif
 
@@ -226,7 +226,7 @@ static inline uint8_t bswap_u8(uint8_t n) {
 
 // C23 polyfill: bit utilities
 
-#if __STDC_VERSION__ >= C23
+#if __STDC_VERSION_STDBIT_H__ >= C23
 #  define count_ones stdc_count_ones
 #  define count_zeros stdc_count_zeros
 #  define leading_zeros stdc_leading_zeros
@@ -374,7 +374,7 @@ UINT_OVERLOADS(BIT_CEIL)
 #define bit_floor(n) UINT_SELECT(n, bit_floor)(n)
 #define bit_ceil(n) UINT_SELECT(n, bit_ceil)(n)
 
-#endif // __STDC_VERSION__ < C23
+#endif // __STDC_VERSION_STDBIT_H__ < C23
 
 #define ROTATE_LEFT(type, suffix, width) \
 	static inline type rotate_left##suffix(type n, int c) { \
diff --git a/src/prelude.h b/src/prelude.h
index 3521fe8..c4edcb2 100644
--- a/src/prelude.h
+++ b/src/prelude.h
@@ -50,6 +50,9 @@ extern const char bfs_version[];
 #if __has_include(<paths.h>)
 #  define BFS_HAS_PATHS_H true
 #endif
+#if __has_include(<stdbit.h>)
+#  define BFS_HAS_STDBIT_H true
+#endif
 #if __has_include(<sys/extattr.h>)
 #  define BFS_HAS_SYS_EXTATTR_H true
 #endif
@@ -76,6 +79,7 @@ extern const char bfs_version[];
 
 #define BFS_HAS_MNTENT_H __GLIBC__
 #define BFS_HAS_PATHS_H true
+#define BFS_HAS_STDBIT_H (__STDC_VERSION__ >= C23)
 #define BFS_HAS_SYS_EXTATTR_H __FreeBSD__
 #define BFS_HAS_SYS_MKDEV_H false
 #define BFS_HAS_SYS_PARAM_H true
-- 
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