Guard inclusion of emmintrin.h Guard inclusion of emmintrin.h with "#ifdef __SSE2__". The gcc version of this header, xmmintrin.h, and mmintrin.h check that the appropriate defines are set before defining anything (are internally guarded). However the clang versions of these includes are not internally guarded. As a result of this, externally guard the inclusion of these headers.
diff --git a/src/smooth/ftgrays.c b/src/smooth/ftgrays.c
index 7158cd2..5e04ff4 100644
--- a/src/smooth/ftgrays.c
+++ b/src/smooth/ftgrays.c
@@ -1009,7 +1009,9 @@ typedef ptrdiff_t FT_PtrDist;
#if BEZIER_USE_DDA
+#ifdef __SSE2__
#include <emmintrin.h>
+#endif
static void
gray_render_conic( RAS_ARG_ const FT_Vector* control,