From 8eb18cdb65e3fd6111fc50ac5a69d3f7094dd54c Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Mon, 4 Nov 2024 11:53:18 -0500
Subject: diag: New bfs_unreachable() and bfs_assume() macros

---
 src/diag.h | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/src/diag.h b/src/diag.h
index 3bea9b2..bc741cf 100644
--- a/src/diag.h
+++ b/src/diag.h
@@ -12,6 +12,7 @@
 #include "bfstd.h"
 
 #include <stdarg.h>
+#include <stddef.h>
 
 /**
  * A source code location.
@@ -126,6 +127,37 @@ void bfs_abortf(const struct bfs_loc *loc, const char *format, ...);
 #  define bfs_eassert bfs_everify
 #endif
 
+/** @internal Wrapper for unreachable(). */
+#ifdef unreachable
+#  define bfs_unreachable_ unreachable
+#elif __has_builtin(__builtin_unreachable)
+#  define bfs_unreachable_ __builtin_unreachable
+#else
+_noreturn
+static inline void bfs_unreachable_(void) {
+}
+#endif
+
+/**
+ * Abort in debug builds; unreachable in release builds.
+ */
+#ifdef NDEBUG
+#  define bfs_unreachable(...) bfs_unreachable_()
+#else
+#  define bfs_unreachable bfs_abort
+#endif
+
+/**
+ * Assert in debug builds; assume in release builds.
+ */
+#ifdef NDEBUG
+#  define bfs_assume(...) bfs_assume_(__VA_ARGS__, )
+#  define bfs_assume_(cond, ...) \
+	((cond) ? (void)0 : bfs_unreachable_())
+#else
+#  define bfs_assume bfs_assert
+#endif
+
 struct bfs_ctx;
 struct bfs_expr;
 
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