From 8bdaa529df668d0f868d82be39ddbffe9626f5e7 Mon Sep 17 00:00:00 2001
From: Andrei Alexeyev <akari@taisei-project.org>
Date: Tue, 24 Sep 2019 22:58:05 +0300
Subject: [PATCH] fix for platforms where alignof(max_align_t) < 16

i686 windows in particular
---
 meson.build       |  2 +-
 src/list.h        |  6 +++++-
 src/util/compat.h | 23 ++++++++++-------------
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/meson.build b/meson.build
index e2ceb96f..7b057457 100644
--- a/meson.build
+++ b/meson.build
@@ -188,7 +188,7 @@ config.set('TAISEI_BUILDCONF_HAVE_TIMESPEC', have_timespec)
 config.set('TAISEI_BUILDCONF_HAVE_INT128', cc.sizeof('__int128') == 16)
 config.set('TAISEI_BUILDCONF_HAVE_LONG_DOUBLE', cc.sizeof('long double') > 8)
 config.set('TAISEI_BUILDCONF_HAVE_POSIX', have_posix)
-config.set('TAISEI_BUILDCONF_HAVE_MAX_ALIGN_T', cc.compiles('#include <stddef.h>\nmax_align_t i;', name : 'max_align_t test'))
+config.set('TAISEI_BUILDCONF_MALLOC_ALIGNMENT', cc.alignment('max_align_t', prefix : '#include <stddef.h>\n'))
 
 prefer_relpath_systems = [
     'windows',
diff --git a/src/list.h b/src/list.h
index c825566e..e68cf4b4 100644
--- a/src/list.h
+++ b/src/list.h
@@ -11,7 +11,11 @@
 
 #include "taisei.h"
 
-#define LIST_ALIGN alignas(16)
+#if TAISEI_BUILDCONF_MALLOC_ALIGNMENT < 16
+	#define LIST_ALIGN alignas(TAISEI_BUILDCONF_MALLOC_ALIGNMENT)
+#else
+	#define LIST_ALIGN alignas(16)
+#endif
 
 typedef struct ListInterface ListInterface;
 typedef struct List List;
diff --git a/src/util/compat.h b/src/util/compat.h
index 4cf1673c..e55c2d83 100644
--- a/src/util/compat.h
+++ b/src/util/compat.h
@@ -155,8 +155,12 @@ typedef _Complex double complex;
 // `CMPLX` like ((double complex){ x, y })
 #undef CMPLX
 
-#ifndef TAISEI_BUILDCONF_HAVE_MAX_ALIGN_T
-typedef complex max_align_t;
+// FIXME this is likely incorrect!
+#if TAISEI_BUILDCONF_MALLOC_ALIGNMENT < 0
+	#warning max_align_t not supported
+	#undef TAISEI_BUILDCONF_MALLOC_ALIGNMENT
+	#define TAISEI_BUILDCONF_MALLOC_ALIGNMENT 8
+	typedef struct { alignas(TAISEI_BUILDCONF_MALLOC_ALIGNMENT) long double a; } max_align_t;
 #endif
 
 // In case the C11 CMPLX macro is not present, try our best to provide a substitute
@@ -264,19 +268,12 @@ typedef complex max_align_t;
 
 #define INLINE static inline attr_must_inline __attribute__((gnu_inline, artificial))
 
-#ifdef NDEBUG
-	#define _ensure_aligned(ptr, alignment) (ptr)
-#else
-	INLINE void *_ensure_aligned(void *ptr, size_t alignment) {
-		assert(((uintptr_t)ptr & (alignment - 1)) == 0);
-		return ptr;
-	}
-#endif
-
 #ifdef USE_GNU_EXTENSIONS
 	#define ASSUME_ALIGNED(expr, alignment) (__extension__ ({ \
-		assert(__builtin_constant_p(alignment)); \
-		__builtin_assume_aligned(_ensure_aligned((expr), (alignment)), (alignment)); \
+		static_assert(__builtin_constant_p(alignment), ""); \
+		__auto_type _assume_aligned_ptr = (expr); \
+		assert(((uintptr_t)_assume_aligned_ptr & ((alignment) - 1)) == 0); \
+		__builtin_assume_aligned(_assume_aligned_ptr, (alignment)); \
 	}))
 #else
 	#define ASSUME_ALIGNED(expr, alignment) (expr)