diff --git a/ThunkLibs/libEGL/libEGL_interface.cpp b/ThunkLibs/libEGL/libEGL_interface.cpp
index 7d681948e..c9bb2d1cc 100644
--- a/ThunkLibs/libEGL/libEGL_interface.cpp
+++ b/ThunkLibs/libEGL/libEGL_interface.cpp
@@ -7,6 +7,10 @@ struct fex_gen_config {
     unsigned version = 1;
 };
 
+// Function, parameter index, parameter type [optional]
+template<auto, int, typename = void>
+struct fex_gen_param {};
+
 template<> struct fex_gen_config<eglBindAPI> {};
 template<> struct fex_gen_config<eglChooseConfig> {};
 template<> struct fex_gen_config<eglDestroyContext> {};
@@ -23,4 +27,7 @@ template<> struct fex_gen_config<eglCreateWindowSurface> {};
 template<> struct fex_gen_config<eglGetCurrentContext> {};
 template<> struct fex_gen_config<eglGetCurrentDisplay> {};
 template<> struct fex_gen_config<eglGetCurrentSurface> {};
+
+// EGLNativeDisplayType is a pointer to opaque data (wl_display/(X)Display/...)
 template<> struct fex_gen_config<eglGetDisplay> {};
+template<> struct fex_gen_param<eglGetDisplay, 0, EGLNativeDisplayType> : fexgen::assume_compatible_data_layout {};
diff --git a/ThunkLibs/libGL/libGL_interface.cpp b/ThunkLibs/libGL/libGL_interface.cpp
index e292b2e05..d05c0cbab 100644
--- a/ThunkLibs/libGL/libGL_interface.cpp
+++ b/ThunkLibs/libGL/libGL_interface.cpp
@@ -11,6 +11,8 @@
 #undef GL_ARB_viewport_array
 #include "glcorearb.h"
 
+#include <type_traits>
+
 template<auto>
 struct fex_gen_config {
     unsigned version = 1;
@@ -18,6 +20,25 @@ struct fex_gen_config {
 
 template<> struct fex_gen_config<glXGetProcAddress> : fexgen::custom_guest_entrypoint, fexgen::returns_guest_pointer {};
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<std::remove_pointer_t<GLXContext>> : fexgen::opaque_type {};
+template<> struct fex_gen_type<std::remove_pointer_t<GLXFBConfig>> : fexgen::opaque_type {};
+template<> struct fex_gen_type<std::remove_pointer_t<GLsync>> : fexgen::opaque_type {};
+
+// NOTE: These should be opaque, but actually aren't because the respective libraries aren't thunked
+template<> struct fex_gen_type<_cl_context> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_cl_event> : fexgen::opaque_type {};
+
+// Opaque for the purpose of libGL
+template<> struct fex_gen_type<_XDisplay> : fexgen::opaque_type {};
+
+#ifndef IS_32BIT_THUNK
+// TODO: These are largely compatible, *but* contain function pointer members that need adjustment!
+template<> struct fex_gen_type<XExtData> : fexgen::assume_compatible_data_layout {};
+#endif
+
 // Symbols queryable through glXGetProcAddr
 namespace internal {
 template<auto>
diff --git a/ThunkLibs/libX11/libX11_Guest.cpp b/ThunkLibs/libX11/libX11_Guest.cpp
index b32ad9228..3a2547a76 100644
--- a/ThunkLibs/libX11/libX11_Guest.cpp
+++ b/ThunkLibs/libX11/libX11_Guest.cpp
@@ -14,6 +14,8 @@ extern "C" {
 #include <X11/Xproto.h>
 #include <X11/XKBlib.h>
 
+#include <X11/extensions/extutil.h>
+
 // Include Xlibint.h and undefine some of its macros that clash with the standard library
 #include <X11/Xlibint.h>
 #undef min
diff --git a/ThunkLibs/libX11/libX11_Host.cpp b/ThunkLibs/libX11/libX11_Host.cpp
index c73d7a6ea..568543a70 100644
--- a/ThunkLibs/libX11/libX11_Host.cpp
+++ b/ThunkLibs/libX11/libX11_Host.cpp
@@ -20,12 +20,20 @@ extern "C" {
 #undef min
 #undef max
 
+#define XTRANS_SEND_FDS 1
+#include <X11/Xtrans/Xtransint.h>
+
 #include <X11/Xutil.h>
+#include <X11/Xregion.h>
 #include <X11/Xresource.h>
 
 #include <X11/Xproto.h>
 
+#include <X11/extensions/extutil.h>
 #include <X11/extensions/XKBstr.h>
+#include <X11/extensions/XKBgeom.h>
+
+#include <X11/Xtrans/Xtransint.h>
 }
 
 #include "common/Host.h"
diff --git a/ThunkLibs/libX11/libX11_interface.cpp b/ThunkLibs/libX11/libX11_interface.cpp
index 188826056..15675e4fc 100644
--- a/ThunkLibs/libX11/libX11_interface.cpp
+++ b/ThunkLibs/libX11/libX11_interface.cpp
@@ -10,11 +10,15 @@ extern "C" {
 
 #include <X11/ImUtil.h>
 
+#include <X11/extensions/extutil.h>
 #include <X11/extensions/Xext.h>
+#include <X11/extensions/XKBgeom.h>
 
 #include <X11/Xlibint.h>
 #include <X11/XKBlib.h>
 
+#include <X11/Xtrans/Xtransint.h>
+
 #include <X11/Xutil.h>
 }
 
@@ -28,6 +32,10 @@ struct fex_gen_config {
 template<typename>
 struct fex_gen_type {};
 
+// Function, parameter index, parameter type [optional]
+template<auto, int, typename = void>
+struct fex_gen_param {};
+
 template<> struct fex_gen_type<XID(Display*)> {}; // XDisplay::resource_alloc
 
 // NOTE: only indirect calls to this are allowed
@@ -54,6 +62,61 @@ template<> struct fex_gen_type<unsigned long(XImage*, int, int)> {};      // XIm
 template<> struct fex_gen_type<int(XImage*, int, int, unsigned long)> {}; // XImage::f.put_pixel
 template<> struct fex_gen_type<int(XImage*, long)> {};                    // XImage::f.add_pixel
 
+template<> struct fex_gen_type<std::remove_pointer_t<XIC>> : fexgen::opaque_type {};
+template<> struct fex_gen_type<std::remove_pointer_t<XIM>> : fexgen::opaque_type {};
+template<> struct fex_gen_type<std::remove_pointer_t<XOC>> : fexgen::opaque_type {};
+template<> struct fex_gen_type<std::remove_pointer_t<XOM>> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XrmHashBucketRec> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XkbInfoRec> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XContextDB> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XDisplayAtoms> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XLockInfo> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XIMFilter> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XErrorThreadInfo> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XKeytrans> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_X11XCBPrivate> : fexgen::opaque_type {};
+
+
+#ifndef IS_32BIT_THUNK
+// This has a public definition but is used as an opaque type in most APIs
+template<> struct fex_gen_type<std::remove_pointer_t<Region>> : fexgen::assume_compatible_data_layout {};
+
+// Union types
+template<> struct fex_gen_type<XEvent> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<xEvent> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<XkbDoodadRec> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<xReply> : fexgen::assume_compatible_data_layout {};
+
+// Union type of all sorts of different X objects... Further, XEHeadOfExtensionList casts this to XExtData**.
+// This is likely highly unsafe to assume compatible.
+template<> struct fex_gen_type<XEDataObject> : fexgen::assume_compatible_data_layout {};
+
+// Linked-list types
+template<> struct fex_gen_type<_XtransConnFd> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XkbDeviceLedChanges> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XQEvent> : fexgen::assume_compatible_data_layout {};
+
+// Contains nontrivial circular pointer relationships
+template<> struct fex_gen_type<XkbOverlayRec> : fexgen::assume_compatible_data_layout {};
+
+// TODO: These are largely compatible, *but* contain function pointer members that need adjustment!
+template<> struct fex_gen_type<_XConnWatchInfo> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<XExtData> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XLockPtrs> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XFreeFuncRec> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XExtension> : fexgen::assume_compatible_data_layout {}; // Also contains linked-list pointers
+template<> struct fex_gen_type<_XConnectionInfo> : fexgen::assume_compatible_data_layout {}; // Also contains linked-list pointers
+template<> struct fex_gen_type<_XInternalAsync> : fexgen::assume_compatible_data_layout {}; // Also contains linked-list pointers
+template<> struct fex_gen_type<_XDisplay> : fexgen::assume_compatible_data_layout {};
+
+// TODO: This contains a nested struct type of function pointer members
+template<> struct fex_gen_type<XImage> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<XExtensionHooks> : fexgen::assume_compatible_data_layout {};
+#endif
+
+// Union type (each member is defined in terms of char members)
+template<> struct fex_gen_type<XkbAction> : fexgen::assume_compatible_data_layout {};
+
 // Xlibint
 template<> struct fex_gen_config<_XGetRequest> {};
 template<> struct fex_gen_config<_XFlushGCCache> {};
diff --git a/ThunkLibs/libXext/libXext_Guest.cpp b/ThunkLibs/libXext/libXext_Guest.cpp
index 0db7e4dab..e8684b83f 100644
--- a/ThunkLibs/libXext/libXext_Guest.cpp
+++ b/ThunkLibs/libXext/libXext_Guest.cpp
@@ -35,6 +35,8 @@ extern "C" {
 #include <X11/extensions/syncconst.h>
 #include <X11/extensions/syncproto.h>
 //#include <X11/extensions/XTest.h>
+#undef min
+#undef max
 
 
 #include "common/Guest.h"
diff --git a/ThunkLibs/libXext/libXext_Host.cpp b/ThunkLibs/libXext/libXext_Host.cpp
index 94caa6be0..076087b80 100644
--- a/ThunkLibs/libXext/libXext_Host.cpp
+++ b/ThunkLibs/libXext/libXext_Host.cpp
@@ -8,6 +8,7 @@ $end_info$
 
 #include <X11/Xlib.h>
 #include <X11/Xlibint.h>
+#include <X11/Xregion.h>
 #include <X11/Xutil.h>
 #include <X11/Xproto.h>
 #include <X11/extensions/Xext.h>
@@ -38,6 +39,12 @@ extern "C" {
 #include <X11/extensions/syncproto.h>
 //#include <X11/extensions/XTest.h>
 
+#define XTRANS_SEND_FDS 1
+#include <X11/Xtrans/Xtransint.h>
+
+#undef min
+#undef max
+
 #include "common/Host.h"
 #include <dlfcn.h>
 
diff --git a/ThunkLibs/libXext/libXext_interface.cpp b/ThunkLibs/libXext/libXext_interface.cpp
index 87b0666bb..18f6ccf1e 100644
--- a/ThunkLibs/libXext/libXext_interface.cpp
+++ b/ThunkLibs/libXext/libXext_interface.cpp
@@ -2,6 +2,7 @@
 
 #include <X11/Xlib.h>
 #include <X11/Xlibint.h>
+#include <X11/Xregion.h>
 #include <X11/extensions/Xext.h>
 #include <X11/extensions/dpms.h>
 #include <X11/extensions/XEVI.h>
@@ -16,12 +17,52 @@
 extern "C" {
 #include <X11/extensions/extutil.h>
 }
+#include <X11/Xtrans/Xtransint.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 6;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<_X11XCBPrivate> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XContextDB> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XDisplayAtoms> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XErrorThreadInfo> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XIMFilter> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XkbInfoRec> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XKeytrans> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XLockInfo> : fexgen::opaque_type {};
+template<> struct fex_gen_type<_XrmHashBucketRec> : fexgen::opaque_type {};
+
+#ifndef IS_32BIT_THUNK
+// Union types
+template<> struct fex_gen_type<XEvent> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<xEvent> : fexgen::assume_compatible_data_layout {};
+
+// Linked-list types
+template<> struct fex_gen_type<_XtransConnFd> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XQEvent> : fexgen::assume_compatible_data_layout {};
+
+// TODO: These are largely compatible, *but* contain function pointer members that need adjustment!
+template<> struct fex_gen_type<_XConnectionInfo> : fexgen::assume_compatible_data_layout {}; // Also contains linked-list pointers
+template<> struct fex_gen_type<_XConnWatchInfo> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XDisplay> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<XExtData> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<XExtDisplayInfo> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XExtension> : fexgen::assume_compatible_data_layout {}; // Also contains linked-list pointers
+template<> struct fex_gen_type<_XInternalAsync> : fexgen::assume_compatible_data_layout {}; // Also contains linked-list pointers
+
+// Contains nontrivial circular pointer relationships
+template<> struct fex_gen_type<Screen> : fexgen::assume_compatible_data_layout {};
+
+// TODO: This contains a nested struct type of function pointer members
+template<> struct fex_gen_type<XImage> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<XExtensionHooks> : fexgen::assume_compatible_data_layout {};
+#endif
+
 template<> struct fex_gen_config<DPMSCapable> {};
 template<> struct fex_gen_config<DPMSDisable> {};
 template<> struct fex_gen_config<DPMSEnable> {};
diff --git a/ThunkLibs/libXfixes/libXfixes_Host.cpp b/ThunkLibs/libXfixes/libXfixes_Host.cpp
index b6a0a5ca9..0712fb90a 100644
--- a/ThunkLibs/libXfixes/libXfixes_Host.cpp
+++ b/ThunkLibs/libXfixes/libXfixes_Host.cpp
@@ -6,9 +6,14 @@ $end_info$
 
 #include <stdio.h>
 
+extern "C" {
 #include <X11/Xlib.h>
+#include <X11/Xlibint.h>
 #include <X11/Xutil.h>
 #include <X11/extensions/Xfixes.h>
+}
+#undef min
+#undef max
 
 #include "common/Host.h"
 #include <dlfcn.h>
diff --git a/ThunkLibs/libXfixes/libXfixes_interface.cpp b/ThunkLibs/libXfixes/libXfixes_interface.cpp
index 1bd6df682..24c2227a4 100644
--- a/ThunkLibs/libXfixes/libXfixes_interface.cpp
+++ b/ThunkLibs/libXfixes/libXfixes_interface.cpp
@@ -1,12 +1,24 @@
 #include <common/GeneratorInterface.h>
 
+extern "C" {
 #include <X11/extensions/Xfixes.h>
+#include <X11/Xlibint.h>
+}
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 3;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+#ifndef IS_32BIT_THUNK
+// TODO: These are largely compatible, *but* contain function pointer members that need adjustment!
+template<> struct fex_gen_type<XExtData> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XDisplay> : fexgen::assume_compatible_data_layout {};
+#endif
+
 template<> struct fex_gen_config<XFixesGetCursorName> {};
 template<> struct fex_gen_config<XFixesQueryExtension> {};
 template<> struct fex_gen_config<XFixesQueryVersion> {};
diff --git a/ThunkLibs/libXrender/libXrender_Host.cpp b/ThunkLibs/libXrender/libXrender_Host.cpp
index 49d01d88c..04dbb4a77 100644
--- a/ThunkLibs/libXrender/libXrender_Host.cpp
+++ b/ThunkLibs/libXrender/libXrender_Host.cpp
@@ -6,9 +6,15 @@ $end_info$
 
 #include <stdio.h>
 
+extern "C" {
 #include <X11/Xlib.h>
+#include <X11/Xlibint.h>
+#include <X11/Xregion.h>
 #include <X11/Xutil.h>
 #include <X11/extensions/Xrender.h>
+}
+#undef min
+#undef max
 
 #include "common/Host.h"
 #include <dlfcn.h>
diff --git a/ThunkLibs/libXrender/libXrender_interface.cpp b/ThunkLibs/libXrender/libXrender_interface.cpp
index e884c286e..12424de42 100644
--- a/ThunkLibs/libXrender/libXrender_interface.cpp
+++ b/ThunkLibs/libXrender/libXrender_interface.cpp
@@ -2,11 +2,28 @@
 
 #include <X11/extensions/Xrender.h>
 
+#include <type_traits>
+
 template<auto>
 struct fex_gen_config {
     unsigned version = 1;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+// Struct with multi-dimensional array member. Compatible data layout across all architectures
+template<> struct fex_gen_type<_XTransform> : fexgen::assume_compatible_data_layout {};
+
+#ifndef IS_32BIT_THUNK
+// This has a public definition but is used as an opaque type in most APIs
+template<> struct fex_gen_type<std::remove_pointer_t<Region>> : fexgen::assume_compatible_data_layout {};
+
+// TODO: These are largely compatible, *but* contain function pointer members that need adjustment!
+template<> struct fex_gen_type<XExtData> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<_XDisplay> : fexgen::assume_compatible_data_layout {};
+#endif
+
 template<> struct fex_gen_config<XRenderCreateAnimCursor> {};
 template<> struct fex_gen_config<XRenderCreateCursor> {};
 template<> struct fex_gen_config<XRenderCreateGlyphSet> {};
diff --git a/ThunkLibs/libasound/libasound_interface.cpp b/ThunkLibs/libasound/libasound_interface.cpp
index 7e34d5ce4..e7f101e3f 100644
--- a/ThunkLibs/libasound/libasound_interface.cpp
+++ b/ThunkLibs/libasound/libasound_interface.cpp
@@ -3,11 +3,99 @@
 #include <alsa/asoundlib.h>
 #include <alsa/version.h>
 
+#include <type_traits>
+
 template<auto>
 struct fex_gen_config {
     unsigned version = 2;
 };
 
+// Function, parameter index, parameter type [optional]
+template<auto, int, typename = void>
+struct fex_gen_param {};
+
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<snd_pcm_status_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_shm_area> : fexgen::opaque_type {};
+
+template<> struct fex_gen_type<snd_async_handler_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<std::remove_pointer_t<snd_config_iterator_t>> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_config_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_config_update_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_ctl_card_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_ctl_elem_id_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_ctl_elem_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_ctl_elem_list_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_ctl_elem_value_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_ctl_event_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_ctl_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_devname_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_hctl_elem_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_hctl_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_hwdep_dsp_image_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_hwdep_dsp_status_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_hwdep_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_hwdep_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_input_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_midi_event_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_mixer_class_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_mixer_elem_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_mixer_selem_id_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_mixer_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_output_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_access_mask_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_format_mask_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_hook_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_hw_params_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_scope_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_subformat_mask_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_sw_params_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_pcm_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_rawmidi_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_rawmidi_params_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_rawmidi_status_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_rawmidi_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_sctl_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_client_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_client_pool_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_ev_ext_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_port_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_port_subscribe_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_query_subscribe_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_queue_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_queue_status_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_queue_tempo_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_queue_timer_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_remove_events_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_system_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_seq_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_ginfo_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_gparams_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_gstatus_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_id_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_info_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_params_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_query_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_status_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timer_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<snd_timestamp_t> : fexgen::opaque_type {};
+
+template<> struct fex_gen_type<FILE> : fexgen::opaque_type {};
+
+// Union types with compatible data layout
+template<> struct fex_gen_type<snd_pcm_sync_id_t> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<snd_seq_timestamp> : fexgen::assume_compatible_data_layout {};
+// Has anonymous union member
+template<> struct fex_gen_type<snd_seq_event> : fexgen::assume_compatible_data_layout {};
+
+#ifndef IS_32BIT_THUNK
+// TODO: Convert vtable
+template<> struct fex_gen_type<snd_pcm_scope_ops_t> : fexgen::assume_compatible_data_layout {};
+#endif
+
 template<> struct fex_gen_config<snd_asoundlib_version> {};
 #if SND_LIB_VERSION < ((1 << 16) | (2 << 8) | (6))
 // Exists on 1.2.6
diff --git a/ThunkLibs/libdrm/libdrm_interface.cpp b/ThunkLibs/libdrm/libdrm_interface.cpp
index a8075531e..f64cc2204 100644
--- a/ThunkLibs/libdrm/libdrm_interface.cpp
+++ b/ThunkLibs/libdrm/libdrm_interface.cpp
@@ -7,6 +7,21 @@ struct fex_gen_config {
     unsigned version = 2;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+#ifndef IS_32BIT_THUNK
+// Union types with compatible data layout
+template<> struct fex_gen_type<drmDevice> : fexgen::assume_compatible_data_layout {};
+
+// Anonymous sub-structs
+template<> struct fex_gen_type<drmStatsT> : fexgen::assume_compatible_data_layout {};
+
+// TODO: Convert vtable
+template<> struct fex_gen_type<drmServerInfo> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<drmEventContext> : fexgen::assume_compatible_data_layout {};
+#endif
+
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
 
diff --git a/ThunkLibs/libvulkan/Guest.cpp b/ThunkLibs/libvulkan/Guest.cpp
index 066e1a6b4..cbad026a1 100644
--- a/ThunkLibs/libvulkan/Guest.cpp
+++ b/ThunkLibs/libvulkan/Guest.cpp
@@ -4,6 +4,8 @@ tags: thunklibs|Vulkan
 $end_info$
 */
 
+#define VK_USE_64_BIT_PTR_DEFINES 0
+
 #define VK_USE_PLATFORM_XLIB_XRANDR_EXT
 #define VK_USE_PLATFORM_XLIB_KHR
 #define VK_USE_PLATFORM_XCB_KHR
diff --git a/ThunkLibs/libvulkan/Host.cpp b/ThunkLibs/libvulkan/Host.cpp
index 8e5b333dc..b3f11a7ab 100644
--- a/ThunkLibs/libvulkan/Host.cpp
+++ b/ThunkLibs/libvulkan/Host.cpp
@@ -4,6 +4,8 @@ tags: thunklibs|Vulkan
 $end_info$
 */
 
+#define VK_USE_64_BIT_PTR_DEFINES 0
+
 #define VK_USE_PLATFORM_XLIB_XRANDR_EXT
 #define VK_USE_PLATFORM_XLIB_KHR
 #define VK_USE_PLATFORM_XCB_KHR
@@ -91,8 +93,8 @@ static void FEXFN_IMPL(vkFreeMemory)(VkDevice a_0, VkDeviceMemory a_1, const VkA
   LDR_PTR(vkFreeMemory)(a_0, a_1, nullptr);
 }
 
-static VkResult FEXFN_IMPL(vkCreateDebugReportCallbackEXT)(VkInstance a_0, const VkDebugReportCallbackCreateInfoEXT* a_1, const VkAllocationCallbacks* a_2, VkDebugReportCallbackEXT* a_3) {
-  VkDebugReportCallbackCreateInfoEXT overridden_callback = *a_1;
+static VkResult FEXFN_IMPL(vkCreateDebugReportCallbackEXT)(VkInstance a_0, guest_layout<const VkDebugReportCallbackCreateInfoEXT*> a_1, const VkAllocationCallbacks* a_2, VkDebugReportCallbackEXT* a_3) {
+  VkDebugReportCallbackCreateInfoEXT overridden_callback = *a_1.data;
   overridden_callback.pfnCallback = DummyVkDebugReportCallback;
   (void*&)LDR_PTR(vkCreateDebugReportCallbackEXT) = (void*)LDR_PTR(vkGetInstanceProcAddr)(a_0, "vkCreateDebugReportCallbackEXT");
   return LDR_PTR(vkCreateDebugReportCallbackEXT)(a_0, &overridden_callback, nullptr, a_3);
@@ -103,6 +105,21 @@ static void FEXFN_IMPL(vkDestroyDebugReportCallbackEXT)(VkInstance a_0, VkDebugR
   LDR_PTR(vkDestroyDebugReportCallbackEXT)(a_0, a_1, nullptr);
 }
 
+extern "C" VkBool32 DummyVkDebugUtilsMessengerCallback(
+    VkDebugUtilsMessageSeverityFlagBitsEXT, VkDebugUtilsMessageTypeFlagsEXT,
+    const VkDebugUtilsMessengerCallbackDataEXT*, void*) {
+  return VK_FALSE;
+}
+
+static VkResult FEXFN_IMPL(vkCreateDebugUtilsMessengerEXT)(
+    VkInstance_T* a_0, guest_layout<const VkDebugUtilsMessengerCreateInfoEXT*> a_1,
+    const VkAllocationCallbacks* a_2, VkDebugUtilsMessengerEXT* a_3) {
+  VkDebugUtilsMessengerCreateInfoEXT overridden_callback = *a_1.data;
+  overridden_callback.pfnUserCallback = DummyVkDebugUtilsMessengerCallback;
+  (void*&)LDR_PTR(vkCreateDebugUtilsMessengerEXT) = (void*)LDR_PTR(vkGetInstanceProcAddr)(a_0, "vkCreateDebugUtilsMessengerEXT");
+  return LDR_PTR(vkCreateDebugUtilsMessengerEXT)(a_0, &overridden_callback, nullptr, a_3);
+}
+
 static PFN_vkVoidFunction FEXFN_IMPL(vkGetDeviceProcAddr)(VkDevice a_0, const char* a_1) {
   // Just return the host facing function pointer
   // The guest will handle mapping if this exists
diff --git a/ThunkLibs/libvulkan/libvulkan_interface.cpp b/ThunkLibs/libvulkan/libvulkan_interface.cpp
index abc8d8b86..ba50a1842 100644
--- a/ThunkLibs/libvulkan/libvulkan_interface.cpp
+++ b/ThunkLibs/libvulkan/libvulkan_interface.cpp
@@ -1,10 +1,19 @@
 #include <common/GeneratorInterface.h>
 
+#include <type_traits>
+
 template<auto>
 struct fex_gen_config {
     unsigned version = 1;
 };
 
+// Some of Vulkan's handle types are so-called "non-dispatchable handles".
+// On 64-bit, these are defined as dedicated types by default, which makes
+// annotating these handle types unnecessarily complicated. Instead, setting
+// the following define will make the Vulkan headers alias all handle types
+// to uint64_t.
+#define VK_USE_64_BIT_PTR_DEFINES 0
+
 #define VK_USE_PLATFORM_XLIB_XRANDR_EXT
 #define VK_USE_PLATFORM_XLIB_KHR
 #define VK_USE_PLATFORM_XCB_KHR
@@ -14,6 +23,52 @@ struct fex_gen_config {
 template<> struct fex_gen_config<vkGetDeviceProcAddr> : fexgen::custom_host_impl, fexgen::custom_guest_entrypoint, fexgen::returns_guest_pointer {};
 template<> struct fex_gen_config<vkGetInstanceProcAddr> : fexgen::custom_host_impl, fexgen::custom_guest_entrypoint, fexgen::returns_guest_pointer {};
 
+template<typename>
+struct fex_gen_type {};
+
+// So-called "dispatchable" handles are represented as opaque pointers.
+// In addition to marking them as such, API functions that create these objects
+// need special care since they wrap these handles in another pointer, which
+// the thunk generator can't automatically handle.
+//
+// So-called "non-dispatchable" handles don't need this extra treatment, since
+// they are uint64_t IDs on both 32-bit and 64-bit systems.
+template<> struct fex_gen_type<VkCommandBuffer_T> : fexgen::opaque_type {};
+template<> struct fex_gen_type<VkDevice_T> : fexgen::opaque_type {};
+template<> struct fex_gen_type<VkInstance_T> : fexgen::opaque_type {};
+template<> struct fex_gen_type<VkPhysicalDevice_T> : fexgen::opaque_type {};
+template<> struct fex_gen_type<VkQueue_T> : fexgen::opaque_type {};
+
+// Mark union types with compatible layout as such
+// TODO: These may still have different alignment requirements!
+template<> struct fex_gen_type<VkClearValue> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<VkClearColorValue> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<VkPipelineExecutableStatisticValueKHR> : fexgen::assume_compatible_data_layout {};
+#ifndef IS_32BIT_THUNK
+template<> struct fex_gen_type<VkAccelerationStructureGeometryDataKHR> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<VkDescriptorDataEXT> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<VkDeviceOrHostAddressKHR> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<VkDeviceOrHostAddressConstKHR> : fexgen::assume_compatible_data_layout {};
+template<> struct fex_gen_type<VkPerformanceValueDataINTEL> : fexgen::assume_compatible_data_layout {};
+#endif
+
+#ifndef IS_32BIT_THUNK
+// The pNext member of this is a pointer to another VkBaseOutStructure, so data layout compatibility can't be inferred automatically
+template<> struct fex_gen_type<VkBaseOutStructure> : fexgen::assume_compatible_data_layout {};
+#endif
+
+
+// TODO: Should not be opaque, but it's usually NULL anyway. Supporting the contained function pointers will need more work.
+template<> struct fex_gen_type<VkAllocationCallbacks> : fexgen::opaque_type {};
+
+// X11 interop
+template<> struct fex_gen_type<Display> : fexgen::opaque_type {};
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
+// Wayland interop
+template<> struct fex_gen_type<wl_display> : fexgen::opaque_type {};
+template<> struct fex_gen_type<wl_surface> : fexgen::opaque_type {};
+
 namespace internal {
 
 // Function, parameter index, parameter type [optional]
@@ -31,6 +86,7 @@ template<> struct fex_gen_config<vkEnumeratePhysicalDevices> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceFeatures> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceFormatProperties> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceImageFormatProperties> {};
+// TODO: Output parameter must repack on exit!
 template<> struct fex_gen_config<vkGetPhysicalDeviceProperties> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceQueueFamilyProperties> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceMemoryProperties> {};
@@ -74,6 +130,7 @@ template<> struct fex_gen_config<vkResetEvent> {};
 template<> struct fex_gen_config<vkCreateQueryPool> {};
 template<> struct fex_gen_config<vkDestroyQueryPool> {};
 template<> struct fex_gen_config<vkGetQueryPoolResults> {};
+template<> struct fex_gen_param<vkGetQueryPoolResults, 5, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCreateBuffer> {};
 template<> struct fex_gen_config<vkDestroyBuffer> {};
 template<> struct fex_gen_config<vkCreateBufferView> {};
@@ -185,6 +242,7 @@ template<> struct fex_gen_config<vkDestroySamplerYcbcrConversion> {};
 template<> struct fex_gen_config<vkCreateDescriptorUpdateTemplate> {};
 template<> struct fex_gen_config<vkDestroyDescriptorUpdateTemplate> {};
 template<> struct fex_gen_config<vkUpdateDescriptorSetWithTemplate> {};
+template<> struct fex_gen_param<vkUpdateDescriptorSetWithTemplate, 3, const void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceExternalBufferProperties> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceExternalFenceProperties> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceExternalSemaphoreProperties> {};
@@ -296,9 +354,11 @@ template<> struct fex_gen_config<vkImportSemaphoreFdKHR> {};
 template<> struct fex_gen_config<vkGetSemaphoreFdKHR> {};
 template<> struct fex_gen_config<vkCmdPushDescriptorSetKHR> {};
 template<> struct fex_gen_config<vkCmdPushDescriptorSetWithTemplateKHR> {};
+template<> struct fex_gen_param<vkCmdPushDescriptorSetWithTemplateKHR, 4, const void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCreateDescriptorUpdateTemplateKHR> {};
 template<> struct fex_gen_config<vkDestroyDescriptorUpdateTemplateKHR> {};
 template<> struct fex_gen_config<vkUpdateDescriptorSetWithTemplateKHR> {};
+template<> struct fex_gen_param<vkUpdateDescriptorSetWithTemplateKHR, 3, const void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCreateRenderPass2KHR> {};
 template<> struct fex_gen_config<vkCmdBeginRenderPass2KHR> {};
 template<> struct fex_gen_config<vkCmdNextSubpass2KHR> {};
@@ -370,6 +430,7 @@ template<> struct fex_gen_config<vkGetDeviceImageSubresourceLayoutKHR> {};
 template<> struct fex_gen_config<vkGetImageSubresourceLayout2KHR> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceCooperativeMatrixPropertiesKHR> {};
 template<> struct fex_gen_config<vkCreateDebugReportCallbackEXT> : fexgen::custom_host_impl {};
+template<> struct fex_gen_param<vkCreateDebugReportCallbackEXT, 1, const VkDebugReportCallbackCreateInfoEXT*> : fexgen::ptr_passthrough {};
 template<> struct fex_gen_config<vkDestroyDebugReportCallbackEXT> : fexgen::custom_host_impl {};
 template<> struct fex_gen_config<vkDebugReportMessageEXT> {};
 template<> struct fex_gen_config<vkDebugMarkerSetObjectTagEXT> {};
@@ -393,6 +454,7 @@ template<> struct fex_gen_config<vkGetImageViewAddressNVX> {};
 template<> struct fex_gen_config<vkCmdDrawIndirectCountAMD> {};
 template<> struct fex_gen_config<vkCmdDrawIndexedIndirectCountAMD> {};
 template<> struct fex_gen_config<vkGetShaderInfoAMD> {};
+template<> struct fex_gen_param<vkGetShaderInfoAMD, 5, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceExternalImageFormatPropertiesNV> {};
 template<> struct fex_gen_config<vkCmdBeginConditionalRenderingEXT> {};
 template<> struct fex_gen_config<vkCmdEndConditionalRenderingEXT> {};
@@ -417,7 +479,8 @@ template<> struct fex_gen_config<vkQueueInsertDebugUtilsLabelEXT> {};
 template<> struct fex_gen_config<vkCmdBeginDebugUtilsLabelEXT> {};
 template<> struct fex_gen_config<vkCmdEndDebugUtilsLabelEXT> {};
 template<> struct fex_gen_config<vkCmdInsertDebugUtilsLabelEXT> {};
-template<> struct fex_gen_config<vkCreateDebugUtilsMessengerEXT> {};
+template<> struct fex_gen_config<vkCreateDebugUtilsMessengerEXT> : fexgen::custom_host_impl {};
+template<> struct fex_gen_param<vkCreateDebugUtilsMessengerEXT, 1, const VkDebugUtilsMessengerCreateInfoEXT*> : fexgen::ptr_passthrough {};
 template<> struct fex_gen_config<vkDestroyDebugUtilsMessengerEXT> {};
 template<> struct fex_gen_config<vkSubmitDebugUtilsMessageEXT> {};
 template<> struct fex_gen_config<vkCmdSetSampleLocationsEXT> {};
@@ -427,6 +490,7 @@ template<> struct fex_gen_config<vkCreateValidationCacheEXT> {};
 template<> struct fex_gen_config<vkDestroyValidationCacheEXT> {};
 template<> struct fex_gen_config<vkMergeValidationCachesEXT> {};
 template<> struct fex_gen_config<vkGetValidationCacheDataEXT> {};
+template<> struct fex_gen_param<vkGetValidationCacheDataEXT, 3, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCmdBindShadingRateImageNV> {};
 template<> struct fex_gen_config<vkCmdSetViewportShadingRatePaletteNV> {};
 template<> struct fex_gen_config<vkCmdSetCoarseSampleOrderNV> {};
@@ -439,11 +503,15 @@ template<> struct fex_gen_config<vkCmdCopyAccelerationStructureNV> {};
 template<> struct fex_gen_config<vkCmdTraceRaysNV> {};
 template<> struct fex_gen_config<vkCreateRayTracingPipelinesNV> {};
 template<> struct fex_gen_config<vkGetRayTracingShaderGroupHandlesKHR> {};
+template<> struct fex_gen_param<vkGetRayTracingShaderGroupHandlesKHR, 5, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkGetRayTracingShaderGroupHandlesNV> {};
+template<> struct fex_gen_param<vkGetRayTracingShaderGroupHandlesNV, 5, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkGetAccelerationStructureHandleNV> {};
+template<> struct fex_gen_param<vkGetAccelerationStructureHandleNV, 3, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCmdWriteAccelerationStructuresPropertiesNV> {};
 template<> struct fex_gen_config<vkCompileDeferredNV> {};
 template<> struct fex_gen_config<vkGetMemoryHostPointerPropertiesEXT> {};
+template<> struct fex_gen_param<vkGetMemoryHostPointerPropertiesEXT, 2, const void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCmdWriteBufferMarkerAMD> {};
 template<> struct fex_gen_config<vkGetPhysicalDeviceCalibrateableTimeDomainsEXT> {};
 template<> struct fex_gen_config<vkGetCalibratedTimestampsEXT> {};
@@ -453,6 +521,7 @@ template<> struct fex_gen_config<vkCmdDrawMeshTasksIndirectCountNV> {};
 template<> struct fex_gen_config<vkCmdSetExclusiveScissorEnableNV> {};
 template<> struct fex_gen_config<vkCmdSetExclusiveScissorNV> {};
 template<> struct fex_gen_config<vkCmdSetCheckpointNV> {};
+template<> struct fex_gen_param<vkCmdSetCheckpointNV, 1, const void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkGetQueueCheckpointDataNV> {};
 template<> struct fex_gen_config<vkInitializePerformanceApiINTEL> {};
 template<> struct fex_gen_config<vkUninitializePerformanceApiINTEL> {};
@@ -537,6 +606,7 @@ template<> struct fex_gen_config<vkCopyMicromapEXT> {};
 template<> struct fex_gen_config<vkCopyMicromapToMemoryEXT> {};
 template<> struct fex_gen_config<vkCopyMemoryToMicromapEXT> {};
 template<> struct fex_gen_config<vkWriteMicromapsPropertiesEXT> {};
+template<> struct fex_gen_param<vkWriteMicromapsPropertiesEXT, 5, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCmdCopyMicromapEXT> {};
 template<> struct fex_gen_config<vkCmdCopyMicromapToMemoryEXT> {};
 template<> struct fex_gen_config<vkCmdCopyMemoryToMicromapEXT> {};
@@ -609,6 +679,7 @@ template<> struct fex_gen_config<vkCopyAccelerationStructureKHR> {};
 template<> struct fex_gen_config<vkCopyAccelerationStructureToMemoryKHR> {};
 template<> struct fex_gen_config<vkCopyMemoryToAccelerationStructureKHR> {};
 template<> struct fex_gen_config<vkWriteAccelerationStructuresPropertiesKHR> {};
+template<> struct fex_gen_param<vkWriteAccelerationStructuresPropertiesKHR, 5, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCmdCopyAccelerationStructureKHR> {};
 template<> struct fex_gen_config<vkCmdCopyAccelerationStructureToMemoryKHR> {};
 template<> struct fex_gen_config<vkCmdCopyMemoryToAccelerationStructureKHR> {};
@@ -619,6 +690,7 @@ template<> struct fex_gen_config<vkGetAccelerationStructureBuildSizesKHR> {};
 template<> struct fex_gen_config<vkCmdTraceRaysKHR> {};
 template<> struct fex_gen_config<vkCreateRayTracingPipelinesKHR> {};
 template<> struct fex_gen_config<vkGetRayTracingCaptureReplayShaderGroupHandlesKHR> {};
+template<> struct fex_gen_param<vkGetRayTracingCaptureReplayShaderGroupHandlesKHR, 5, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<vkCmdTraceRaysIndirectKHR> {};
 template<> struct fex_gen_config<vkGetRayTracingShaderGroupStackSizeKHR> {};
 template<> struct fex_gen_config<vkCmdSetRayTracingPipelineStackSizeKHR> {};
diff --git a/ThunkLibs/libwayland-client/Host.cpp b/ThunkLibs/libwayland-client/Host.cpp
index 8cfcb4693..00a29ef5c 100644
--- a/ThunkLibs/libwayland-client/Host.cpp
+++ b/ThunkLibs/libwayland-client/Host.cpp
@@ -46,7 +46,7 @@ static void WaylandFinalizeHostTrampolineForGuestListener(void (*callback)()) {
 }
 
 extern "C" int fexfn_impl_libwayland_client_wl_proxy_add_listener(struct wl_proxy *proxy,
-      guest_layout<void (**)(void)> callback_raw, guest_layout<void*> data) {
+      guest_layout<void (**)(void)> callback_raw, void* data) {
   auto guest_interface = ((wl_proxy_private*)proxy)->interface;
 
   for (int i = 0; i < guest_interface->event_count; ++i) {
@@ -162,7 +162,7 @@ extern "C" int fexfn_impl_libwayland_client_wl_proxy_add_listener(struct wl_prox
   }
 
   // Pass the original function pointer table to the host wayland library. This ensures the table is valid until the listener is unregistered.
-  return fexldr_ptr_libwayland_client_wl_proxy_add_listener(proxy, callback_raw.data, data.data);
+  return fexldr_ptr_libwayland_client_wl_proxy_add_listener(proxy, callback_raw.data, data);
 }
 
 wl_interface* fexfn_impl_libwayland_client_fex_wl_exchange_interface_pointer(wl_interface* guest_interface, char const* name) {
diff --git a/ThunkLibs/libwayland-client/libwayland-client_interface.cpp b/ThunkLibs/libwayland-client/libwayland-client_interface.cpp
index 32fe6ba37..077e52c93 100644
--- a/ThunkLibs/libwayland-client/libwayland-client_interface.cpp
+++ b/ThunkLibs/libwayland-client/libwayland-client_interface.cpp
@@ -14,6 +14,15 @@ struct fex_gen_type {};
 template<auto, int, typename = void>
 struct fex_gen_param {};
 
+template<> struct fex_gen_type<wl_display> : fexgen::opaque_type {};
+template<> struct fex_gen_type<wl_proxy> : fexgen::opaque_type {};
+template<> struct fex_gen_type<wl_interface> : fexgen::opaque_type {};
+
+template<> struct fex_gen_type<wl_event_queue> : fexgen::opaque_type {};
+
+// Passed over Wayland's wire protocol for some functions
+template<> struct fex_gen_type<wl_array> {};
+
 
 template<> struct fex_gen_config<wl_proxy_destroy> : fexgen::custom_guest_entrypoint {};
 
@@ -36,8 +45,10 @@ template<> struct fex_gen_config<wl_display_get_fd> {};
 template<> struct fex_gen_config<wl_event_queue_destroy> {};
 
 template<> struct fex_gen_config<wl_proxy_add_listener> : fexgen::custom_host_impl, fexgen::custom_guest_entrypoint {};
+// Callback table
 template<> struct fex_gen_param<wl_proxy_add_listener, 1, void(**)()> : fexgen::ptr_passthrough {};
-template<> struct fex_gen_param<wl_proxy_add_listener, 2, void*> : fexgen::ptr_passthrough {};
+// User-provided data pointer (not used in caller-provided callback)
+template<> struct fex_gen_param<wl_proxy_add_listener, 2, void*> : fexgen::assume_compatible_data_layout {};
 template<> struct fex_gen_config<wl_proxy_create> {};
 template<> struct fex_gen_config<wl_proxy_create_wrapper> {};
 template<> struct fex_gen_config<wl_proxy_get_tag> {};
@@ -45,6 +56,7 @@ template<> struct fex_gen_config<wl_proxy_get_user_data> {};
 template<> struct fex_gen_config<wl_proxy_get_version> {};
 template<> struct fex_gen_config<wl_proxy_set_queue> {};
 template<> struct fex_gen_config<wl_proxy_set_tag> {};
+// TODO: This has a void* parameter. Why does 32-bit accept this without annotations?
 template<> struct fex_gen_config<wl_proxy_set_user_data> {};
 template<> struct fex_gen_config<wl_proxy_wrapper_destroy> {};
 
diff --git a/ThunkLibs/libxcb-dri2/libxcb-dri2_interface.cpp b/ThunkLibs/libxcb-dri2/libxcb-dri2_interface.cpp
index 07f93f48d..5a3349c55 100644
--- a/ThunkLibs/libxcb-dri2/libxcb-dri2_interface.cpp
+++ b/ThunkLibs/libxcb-dri2/libxcb-dri2_interface.cpp
@@ -1,12 +1,18 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/dri2.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 0;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
 void FEX_xcb_dri2_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb-dri3/libxcb-dri3_interface.cpp b/ThunkLibs/libxcb-dri3/libxcb-dri3_interface.cpp
index 0708baf23..07d20da64 100644
--- a/ThunkLibs/libxcb-dri3/libxcb-dri3_interface.cpp
+++ b/ThunkLibs/libxcb-dri3/libxcb-dri3_interface.cpp
@@ -1,12 +1,18 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/dri3.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 0;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
 void FEX_xcb_dri3_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb-glx/libxcb-glx_interface.cpp b/ThunkLibs/libxcb-glx/libxcb-glx_interface.cpp
index 28f76fcce..64160def5 100644
--- a/ThunkLibs/libxcb-glx/libxcb-glx_interface.cpp
+++ b/ThunkLibs/libxcb-glx/libxcb-glx_interface.cpp
@@ -1,12 +1,18 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/glx.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 0;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
 void FEX_xcb_glx_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb-present/libxcb-present_interface.cpp b/ThunkLibs/libxcb-present/libxcb-present_interface.cpp
index b1e32b755..69481998b 100644
--- a/ThunkLibs/libxcb-present/libxcb-present_interface.cpp
+++ b/ThunkLibs/libxcb-present/libxcb-present_interface.cpp
@@ -1,12 +1,18 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/present.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 0;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
 void FEX_xcb_present_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb-randr/libxcb-randr_interface.cpp b/ThunkLibs/libxcb-randr/libxcb-randr_interface.cpp
index 4f00b4713..f8eb585ce 100644
--- a/ThunkLibs/libxcb-randr/libxcb-randr_interface.cpp
+++ b/ThunkLibs/libxcb-randr/libxcb-randr_interface.cpp
@@ -1,12 +1,23 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/randr.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 0;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
+// Union type (includes pointers, so only compatible across 64-bit architectures)
+#ifndef IS_32BIT_THUNK
+template<> struct fex_gen_type<xcb_randr_notify_data_t> : fexgen::assume_compatible_data_layout {};
+#endif
+
 void FEX_xcb_randr_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb-shm/libxcb-shm_interface.cpp b/ThunkLibs/libxcb-shm/libxcb-shm_interface.cpp
index 246c0abee..9b61d0570 100644
--- a/ThunkLibs/libxcb-shm/libxcb-shm_interface.cpp
+++ b/ThunkLibs/libxcb-shm/libxcb-shm_interface.cpp
@@ -1,12 +1,18 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/shm.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 0;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
 void FEX_xcb_shm_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb-sync/libxcb-sync_interface.cpp b/ThunkLibs/libxcb-sync/libxcb-sync_interface.cpp
index e810ec019..5fe072f76 100644
--- a/ThunkLibs/libxcb-sync/libxcb-sync_interface.cpp
+++ b/ThunkLibs/libxcb-sync/libxcb-sync_interface.cpp
@@ -1,12 +1,18 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/sync.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 1;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
 void FEX_xcb_sync_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb-xfixes/libxcb-xfixes_interface.cpp b/ThunkLibs/libxcb-xfixes/libxcb-xfixes_interface.cpp
index 3f5c9c1fc..947da6c19 100644
--- a/ThunkLibs/libxcb-xfixes/libxcb-xfixes_interface.cpp
+++ b/ThunkLibs/libxcb-xfixes/libxcb-xfixes_interface.cpp
@@ -1,12 +1,18 @@
 #include <common/GeneratorInterface.h>
 
 #include <xcb/xfixes.h>
+#include <xcb/xcbext.h>
 
 template<auto>
 struct fex_gen_config {
     unsigned version = 0;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+
 void FEX_xcb_xfixes_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxcb/libxcb_interface.cpp b/ThunkLibs/libxcb/libxcb_interface.cpp
index feeff4940..ede74e44b 100644
--- a/ThunkLibs/libxcb/libxcb_interface.cpp
+++ b/ThunkLibs/libxcb/libxcb_interface.cpp
@@ -11,6 +11,15 @@ struct fex_gen_config {
     unsigned version = 1;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xcb_connection_t> : fexgen::opaque_type {};
+template<> struct fex_gen_type<xcb_special_event> : fexgen::opaque_type {};
+
+// Union type with consistent data layout across host/x86/x86-64
+template<> struct fex_gen_type<xcb_client_message_data_t> : fexgen::assume_compatible_data_layout {};
+
 void FEX_xcb_init_extension(xcb_connection_t*, xcb_extension_t*);
 size_t FEX_usable_size(void*);
 void FEX_free_on_host(void*);
diff --git a/ThunkLibs/libxshmfence/libxshmfence_interface.cpp b/ThunkLibs/libxshmfence/libxshmfence_interface.cpp
index cf396ef6d..5b2433da4 100644
--- a/ThunkLibs/libxshmfence/libxshmfence_interface.cpp
+++ b/ThunkLibs/libxshmfence/libxshmfence_interface.cpp
@@ -9,6 +9,11 @@ struct fex_gen_config {
     unsigned version = 1;
 };
 
+template<typename>
+struct fex_gen_type {};
+
+template<> struct fex_gen_type<xshmfence> : fexgen::opaque_type {};
+
 template<> struct fex_gen_config<xshmfence_trigger> {};
 template<> struct fex_gen_config<xshmfence_await> {};
 template<> struct fex_gen_config<xshmfence_query> {};