[Scummvm-tracker] [ScummVM :: Bugs] #16144: LASTEXPRESS: SIGBUS with packed 'struct Message'

[ScummVM :: Bugs]

#16144: LASTEXPRESS: SIGBUS with packed 'struct Message'
---------------------+---------------------------------
Reporter:  dwatteau  |      Owner:  (none)
    Type:  defect    |     Status:  new
Priority:  normal    |  Component:  Engine: LastExpress
 Version:            |   Keywords:
    Game:            |
---------------------+---------------------------------
 Trying to start the game on either a strict-alignment platform, or through
 UBSan on a more regular setup, shows the following problem

 {{{
 User picked target 'lastexpress' (engine ID 'lastexpress', game ID
 'lastexpress')...
 Running The Last Express (Interplay Release/English)
 CD1.HPF: 8c86db47304033fcff32c69fddd5a920, 525522944 bytes.
 CD2.HPF: 58aa26e782d10ec5d2231e539d2fe6a2, 669581312 bytes.
 CD3.HPF: 00554fbf78a2ad391d98578fbbbe1c48, 641128448 bytes.
 HD.HPF: bcc32d977f92bb52c060a0b4e8589cac, 30715904 bytes.

 engines/lastexpress/game/events.h:33:2: runtime error: constructor call on
 misaligned address 0x00012e00d414 for type 'LastExpress::ConsCallParam *',
 which requires 8 byte alignment
 0x00012e00d414: note: pointer points here
   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00
 00  00 00 00 00 00 00 00 00
               ^
 SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
 engines/lastexpress/game/events.h:33:2 in
 engines/lastexpress/game/events.h:33:2: runtime error: constructor call on
 misaligned address 0x00012e00d414 for type 'LastExpress::ConsCallParam *',
 which requires 8 byte alignment
 0x00012e00d414: note: pointer points here
   00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00
 00  00 00 00 00 00 00 00 00
               ^
 SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
 engines/lastexpress/game/events.h:33:2 in
 }}}

 (I'm also attaching a GDB backtrace below, on a device where the engine
 immediately crashes because of this.)

 If I remove the struct packing headers set around `struct Message` in
 `game/events.h`, then the engine appears to run fine, even on that picky
 old MIPS64 netbook of mine. (Not that this weird machine itself matters,
 but strict-alignment issues could cause errors on some ports such as PSP,
 3DS, or some other old ARM devices.)

 Questions are:

 * maybe the struct packing really is here for a good reason,
 * and I don't know if changing this can have an effect on save
 compatibilities, or stuff like that

 Hence this ticket for now ;)
-- 
Ticket URL: <https://bugs.scummvm.org/ticket/16144>
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