From d6d50c69554ac25897fc988d671e8e39780bab92 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Sat, 8 Dec 2018 10:11:11 -0800
Subject: [PATCH] Fix stack alignment in 32-bit Windows builds

Resolves https://github.com/ebiggers/libdeflate/issues/35
---
 libdeflate.h | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/libdeflate.h b/libdeflate.h
index ba9e9b2..678f472 100644
--- a/libdeflate.h
+++ b/libdeflate.h
@@ -22,15 +22,30 @@ extern "C" {
  */
 #ifdef LIBDEFLATE_DLL
 #  ifdef BUILDING_LIBDEFLATE
-#    define LIBDEFLATEAPI LIBEXPORT
+#    define LIBDEFLATEAPI_SYM_VISIBILITY	LIBEXPORT
 #  elif defined(_WIN32) || defined(__CYGWIN__)
-#    define LIBDEFLATEAPI __declspec(dllimport)
+#    define LIBDEFLATEAPI_SYM_VISIBILITY	__declspec(dllimport)
 #  endif
 #endif
-#ifndef LIBDEFLATEAPI
-#  define LIBDEFLATEAPI
+#ifndef LIBDEFLATEAPI_SYM_VISIBILITY
+#  define LIBDEFLATEAPI_SYM_VISIBILITY
 #endif
 
+#if defined(BUILDING_LIBDEFLATE) && defined(__GNUC__) && \
+	defined(_WIN32) && defined(__i386__)
+    /*
+     * On 32-bit Windows, gcc assumes 16-byte stack alignment but MSVC only 4.
+     * Realign the stack when entering libdeflate to avoid crashing in SSE/AVX
+     * code when called from an MSVC-compiled application.
+     */
+#  define LIBDEFLATEAPI_STACKALIGN	__attribute__((force_align_arg_pointer))
+#endif
+#ifndef LIBDEFLATEAPI_STACKALIGN
+#  define LIBDEFLATEAPI_STACKALIGN
+#endif
+
+#define LIBDEFLATEAPI	LIBDEFLATEAPI_SYM_VISIBILITY LIBDEFLATEAPI_STACKALIGN
+
 /* ========================================================================== */
 /*                             Compression                                    */
 /* ========================================================================== */