Fix dhewm3 on 64bit Big Endian platforms like PPC64 BE #626
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
instead of whatever other compression was used there. Fixes crash on Big Endian systems (dhewm#625)
dhewm#625 (comment) confirms that it's broken for the fix, see ocornut/imgui#6732 (comment) ocornut/imgui#5190
to avoid unaligned reads from class members of idClass or its derived classes
All that code is kinda obfuscated, but the integer passing was plain wrong (if sizeof(int) != sizeof(intptr_t), esp. noticeable on Big Endian). data[i] is used by Callbacks.cpp, and for everything but floats it's passed directly as an argument (interpreted as either an integer or a pointer to idVec3 or whatever). So storing an int in there with `( *( int * )&data[ i ] ) = int(...)` only sets the first 4 bytes of that intptr_t, which is 8 bytes on 64bit machines. On Little Endian that just happens to work, on Big Endian it's the wrong 4 bytes.
idInterpreter::Push() is used only for int and (reinterpreted) float values, not pointers (as far as I can tell), so 32bit values on all relevant platforms. It stored its value as intptr_t at `&localstack[ localstackUsed ]` - on 64bit platforms intptr_t is 64bit. Unfortunately, all code reading from the stack just get got a pointer to `&localstack[ localstackUsed ]` in the type they want to read (like `int*` or `float*`) and read that. On Little Endian that happens to work, on 64bit Big Endian it reads the wrong 4 bytes of the intptr_t, so it doesn't work. fixes dhewm#625, dhewm#472
This was referenced Oct 31, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Didn't work, now it at least works better, maybe even as well as Little Endian platforms.