From e7a2c0af762e19c336447e2034ee7ed81f111009 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Fri, 22 Apr 2022 11:24:39 -0700
Subject: Define FUNCTION_CAST in a common header

---
 examples/common/alhelpers.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'examples/common')

diff --git a/examples/common/alhelpers.h b/examples/common/alhelpers.h
index 3752d218..34f73864 100644
--- a/examples/common/alhelpers.h
+++ b/examples/common/alhelpers.h
@@ -18,6 +18,19 @@ void CloseAL(void);
 int altime_get(void);
 void al_nssleep(unsigned long nsec);
 
+/* C doesn't allow casting between function and non-function pointer types, so
+ * with C99 we need to use a union to reinterpret the pointer type. Pre-C99
+ * still needs to use a normal cast and live with the warning (C++ is fine with
+ * a regular reinterpret_cast).
+ */
+#if __STDC_VERSION__ >= 199901L
+#define FUNCTION_CAST(T, ptr) (union{void *p; T f;}){ptr}.f
+#elif defined(__cplusplus)
+#define FUNCTION_CAST(T, ptr) reinterpret_cast<T>(ptr)
+#else
+#define FUNCTION_CAST(T, ptr) (T)(ptr)
+#endif
+
 #ifdef __cplusplus
 } // extern "C"
 #endif
-- 
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