Index: head/multimedia/gstreamer1-libav/files/patch-gst-libs_ext_libav_configure
===================================================================
--- head/multimedia/gstreamer1-libav/files/patch-gst-libs_ext_libav_configure	(revision 484762)
+++ head/multimedia/gstreamer1-libav/files/patch-gst-libs_ext_libav_configure	(revision 484763)
@@ -1,26 +1,58 @@
 --- gst-libs/ext/libav/configure.orig	2018-09-16 15:30:22 UTC
 +++ gst-libs/ext/libav/configure
 @@ -3372,12 +3372,7 @@ target_os_default=$(tolower $(uname -s))
  host_os=$target_os_default
  
  # machine
 -if test "$target_os_default" = aix; then
 -    arch_default=$(uname -p)
 -    strip_default="strip -X32_64"
 -else
 -    arch_default=$(uname -m)
 -fi
 +arch_default=$(uname -p)
  cpu="generic"
  intrinsics="none"
  
-@@ -6492,6 +6487,9 @@ elif enabled llvm_gcc; then
- elif enabled clang; then
+@@ -6487,11 +6482,39 @@ elif enabled gcc; then
+     check_cflags -Wformat
+     check_cflags -fdiagnostics-color=auto
+     enabled extra_warnings || check_disable_warning -Wno-maybe-uninitialized
++    if enabled x86_32; then
++        case $target_os in
++        *bsd*)
++            # BSDs don't guarantee a 16 byte aligned stack, but we can
++            # request GCC to try to maintain 16 byte alignment throughout
++            # function calls. Library entry points that might call assembly
++            # functions align the stack. (The parameter means 2^4 bytes.)
++            check_cflags -mpreferred-stack-boundary=4
++            ;;
++        esac
++    fi
+ elif enabled llvm_gcc; then
      check_cflags -mllvm -stack-alignment=16
-     check_cflags -mstack-alignment=16
+ elif enabled clang; then
+-    check_cflags -mllvm -stack-alignment=16
+-    check_cflags -mstack-alignment=16
 +    if enabled x86_32; then
-+      check_cflags -mstackrealign
++        # Clang doesn't support maintaining alignment without assuming the
++        # same alignment in every function. If 16 byte alignment would be
++        # enabled, one would also have to either add attribute_align_arg on
++        # every single entry point into the libraries or enable -mstackrealign
++        # (doing stack realignment in every single function).
++        case $target_os in
++        mingw32|win32|*bsd*)
++            disable aligned_stack
++            ;;
++        *)
++            check_cflags -mllvm -stack-alignment=16
++            check_cflags -mstack-alignment=16
++            ;;
++        esac
++    else
++        check_cflags -mllvm -stack-alignment=16
++        check_cflags -mstack-alignment=16
 +    fi
      check_cflags -Qunused-arguments
      check_cflags -Werror=implicit-function-declaration
      check_cflags -Werror=missing-prototypes