Fix: decisions being made on uninitialised memory in the SDL video driver #9027
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I think this change should be two commits. One fixes something in SDL, the other fixes something for all video drivers. Also, your commit message is as vague as one can be ;) Maybe a bit more to the point helps a lot in understanding what your change is about to do, instead of having to read that in the code :D
or something? :) |
…tr to be potentially not set
… causing unstoppable fast forward
rubidium42
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TrueBrain
previously approved these changes
Apr 12, 2021
…_ptr to be potentially not set
TrueBrain
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LordAro
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Motivation / Problem
Valgrind:
==27199== Conditional jump or move depends on uninitialised value(s)
==27199== at 0x858DBD: VideoDriver::Tick() (video_driver.cpp:150)
==27199== by 0x85605C: VideoDriver_SDL_Base::LoopOnce() (sdl2_v.cpp:642)
==27199== by 0x85609C: VideoDriver_SDL_Base::MainLoop() (sdl2_v.cpp:660)
==27199== by 0xA44F07: openttd_main(int, char**) (openttd.cpp:837)
==27199== by 0x7A7BB7: main (unix.cpp:262)
==27199==
==27199== Conditional jump or move depends on uninitialised value(s)
==27199== at 0x85632F: VideoDriver_SDL_Base::LockVideoBuffer() (sdl2_v.cpp:721)
==27199== by 0x858E17: VideoDriver::Tick() (video_driver.cpp:160)
==27199== by 0x85605C: VideoDriver_SDL_Base::LoopOnce() (sdl2_v.cpp:642)
==27199== by 0x85609C: VideoDriver_SDL_Base::MainLoop() (sdl2_v.cpp:660)
==27199== by 0xA44F07: openttd_main(int, char**) (openttd.cpp:837)
==27199== by 0x7A7BB7: main (unix.cpp:262)
Description
The issue in VideoDriver::Tick might trigger fast forward if unlucky, since the fast forward booleans could be non-false due to the uninitialised memory. Especially fast_forward_key_pressed is tricky as that only gets set for _DEBUG builds.
The VideoDriver_SDL_Base::LockVideoBuffer might cause locking not to happen when it should, if initialised incorrectly.
Limitations
None
Checklist for review
Some things are not automated, and forgotten often. This list is a reminder for the reviewers.