Describe the bug
On 64 bit platforms (compiling with GCC), there seems to be an aliasing issue within a union for the displaylist struct. The union in question is DynUnion. 2/3 of the union members are 64 bit types on 64 bit platforms (all pointers), but the third is a 32 bit signed integer. Somewhere, the compiler's optimizer or perhaps the code itself is taking a liberty with this size, only copying the first half of the word into the address. On little endian architectures, this is not a big deal, on big endian it means that you get the wrong half of the integer and when processing the display list, instead of getting a parameter for the alpha value, you get an invalid enum (0). This is a show stopping bug, as the game won't start, and gd_printf fails at this point as the entire GL context fails to draw the framebuffer after this (you only get to the title screen before the goddard intro). I had to patch the gd_printf() function to tell me where the code was actually hanging up by doing an addition vprintf() with the va_list.

Fixing this bug was just a matter of promoting the type in that union to a signed 64 bit integer.

Additionally I had to patch the makefile to not sure -march, as for some reason powerpc GCC still varies for these flags (probably dates back to Apple's contributions, but that's not a difficult thing to address).

To Reproduce
Steps to reproduce the behavior:
1.) Compile on powerpc64 (big endian) linux
2.) Launch game

Expected behavior
The game to launch

Desktop (please complete the following information):

• OS: Gentoo ppc64, using nouveau graphics

Additional context
There are still some endianness bugs hiding somewhere in this code. Some of this is due to endianness bugs directly in the nouveau stack (there's a byteswapping texture bug still there that I haven't found the root cause of yet). But, unlike with other games, GL_UNPACK_SWAP_BYTES=1 does not invert the issue, indicating that there's likely some other endianness bugs hiding in gfx_pc.c with regard to the type interpretation (somewhat funny, as the PNG textures are natively big endian, as were most of the assets originally in the game).

Here's the patch to make the game actually launch on powerpc64 linux:

diff --git a/src/goddard/gd_types.h b/src/goddard/gd_types.h
index 0857cc0..547923e 100644
--- a/src/goddard/gd_types.h
+++ b/src/goddard/gd_types.h
@@ -27,11 +27,11 @@ struct GdColour {
 union DynUnion {
     void *ptr;
     char *str;
-    s32 word;
+    s64 word;
 };