https://github.com/g-truc/glm/commit/06ce42e72324b32b1f4c37c646e99950c2bd5f6b.patch
https://bugs.gentoo.org/673972

Not yet applied upstream because <endian.h> is not available on non-Linux platforms.

From 06ce42e72324b32b1f4c37c646e99950c2bd5f6b Mon Sep 17 00:00:00 2001
From: Max Rees <maxcrees@me.com>
Date: Sun, 15 Mar 2020 15:13:27 -0400
Subject: [PATCH] Fix test suite on big endian platforms

---
 glm/gtc/packing.inl      | 55 ++++++++++++++++++++++++++++++++++++++++
 test/gtc/gtc_packing.cpp |  3 ++-
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/glm/gtc/packing.inl b/glm/gtc/packing.inl
index 8c906e16c..b1c99a507 100644
--- a/glm/gtc/packing.inl
+++ b/glm/gtc/packing.inl
@@ -9,6 +9,9 @@
 #include "../detail/type_half.hpp"
 #include <cstring>
 #include <limits>
+extern "C" {
+#include <endian.h>
+}
 
 namespace glm{
 namespace detail
@@ -183,9 +186,15 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			uint x : 3;
 			uint y : 3;
 			uint z : 2;
+#else
+			uint z : 2;
+			uint y : 3;
+			uint x : 3;
+#endif
 		} data;
 		uint8 pack;
 	};
@@ -194,8 +203,13 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			uint x : 4;
 			uint y : 4;
+#else
+			uint y : 4;
+			uint x : 4;
+#endif
 		} data;
 		uint8 pack;
 	};
@@ -204,10 +218,17 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			uint x : 4;
 			uint y : 4;
 			uint z : 4;
 			uint w : 4;
+#else
+			uint w : 4;
+			uint z : 4;
+			uint y : 4;
+			uint x : 4;
+#endif
 		} data;
 		uint16 pack;
 	};
@@ -216,9 +237,15 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			uint x : 5;
 			uint y : 6;
 			uint z : 5;
+#else
+			uint z : 5;
+			uint y : 6;
+			uint x : 5;
+#endif
 		} data;
 		uint16 pack;
 	};
@@ -227,10 +254,17 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			uint x : 5;
 			uint y : 5;
 			uint z : 5;
 			uint w : 1;
+#else
+			uint w : 1;
+			uint z : 5;
+			uint y : 5;
+			uint x : 5;
+#endif
 		} data;
 		uint16 pack;
 	};
@@ -239,10 +273,17 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			uint x : 10;
 			uint y : 10;
 			uint z : 10;
 			uint w : 2;
+#else
+			uint w : 2;
+			uint z : 10;
+			uint y : 10;
+			uint x : 10;
+#endif
 		} data;
 		uint32 pack;
 	};
@@ -251,10 +292,17 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			int x : 10;
 			int y : 10;
 			int z : 10;
 			int w : 2;
+#else
+			int w : 2;
+			int z : 10;
+			int y : 10;
+			int x : 10;
+#endif
 		} data;
 		uint32 pack;
 	};
@@ -263,10 +311,17 @@ namespace detail
 	{
 		struct
 		{
+#if BYTE_ORDER == LITTLE_ENDIAN
 			uint x : 9;
 			uint y : 9;
 			uint z : 9;
 			uint w : 5;
+#else
+			uint w : 5;
+			uint z : 9;
+			uint y : 9;
+			uint x : 9;
+#endif
 		} data;
 		uint32 pack;
 	};
diff --git a/test/gtc/gtc_packing.cpp b/test/gtc/gtc_packing.cpp
index df5b3bb1a..fbaaa5bcc 100644
--- a/test/gtc/gtc_packing.cpp
+++ b/test/gtc/gtc_packing.cpp
@@ -4,6 +4,7 @@
 #include <glm/ext/vector_relational.hpp>
 #include <cstdio>
 #include <vector>
+#include <arpa/inet.h>
 
 void print_bits(float const& s)
 {
@@ -156,7 +157,7 @@ int test_U3x10_1x2()
 
 	glm::u8vec4 const v0(0xff, 0x77, 0x0, 0x33);
 	glm::uint32 const p0 = *reinterpret_cast<glm::uint32 const*>(&v0[0]);
-	glm::uint32 const r0 = 0x330077ff;
+	glm::uint32 const r0 = htonl(0xff770033);
 
 	Error += p0 == r0 ? 0 : 1;