[Scummvm-tracker] [ScummVM :: Bugs] #13416: MOHAWK: Riven: Cannot create a Switch command from data

[ScummVM :: Bugs]

#13416: MOHAWK: Riven: Cannot create a Switch command from data
------------------------+-----------------------------
Reporter:  marcvinyals  |       Owner:  (none)
    Type:  defect       |      Status:  new
Priority:  normal       |   Component:  Engine: Mohawk
 Version:               |  Resolution:
Keywords:               |        Game:  Riven
------------------------+-----------------------------
Comment (by marcvinyals):

 I was able to find (what I believe to be) the source of the problem using
 valgrind, this is what I get:

 {{{
 ==639379== Conditional jump or move depends on uninitialised value(s)
 ==639379==    at 0x40336E:
 Mohawk::RivenScriptManager::createScriptFromData(unsigned int, ...)
 (riven_scripts.cpp:162)
 ==639379==    by 0x412E15:
 Mohawk::RivenStacks::JSpit::xvga1300_carriage(Common::Array<unsigned
 short> const&) (jspit.cpp:309)
 ==639379==    by 0x4143D4: Common::Functor1Mem<Common::Array<unsigned
 short> const&, void,
 Mohawk::RivenStacks::JSpit>::operator()(Common::Array<unsigned short>
 const&) const (func.h:460)
 ==639379==    by 0x408822: Mohawk::RivenStack::runCommand(unsigned short,
 Common::Array<unsigned short> const&) (riven_stack.cpp:186)
 ==639379==    by 0x402367:
 Mohawk::RivenSimpleCommand::runExternalCommand(unsigned short,
 Common::Array<unsigned short> const&) (riven_scripts.cpp:616)
 ==639379==    by 0x4016DD: Mohawk::RivenSimpleCommand::execute()
 (riven_scripts.cpp:826)
 ==639379==    by 0x400D77:
 Mohawk::RivenScript::run(Mohawk::RivenScriptManager*)
 (riven_scripts.cpp:226)
 ==639379==    by 0x400DE2: Mohawk::RivenScriptManager::runQueuedScripts()
 (riven_scripts.cpp:141)
 ==639379==    by 0x3EF383: Mohawk::MohawkEngine_Riven::doFrame()
 (riven.cpp:227)
 ==639379==    by 0x3EFBED: Mohawk::MohawkEngine_Riven::run()
 (riven.cpp:202)
 ==639379==    by 0x3D2544: runGame(Plugin const*, Plugin const*, OSystem&,
 Common::String const&) (main.cpp:318)
 ==639379==    by 0x3D52C2: scummvm_main (main.cpp:627)
 }}}

 Looking around I noticed that in line 170 variable commandCount is used as
 the end condition for the loop, but it would make more sense to use
 variable argumentCount instead. So I tried that and now valgrind is happy
 and I do not hit the bug anymore. I submitted a pull request as
 https://github.com/scummvm/scummvm/pull/3811.

 There is only one other call to createScriptFromData() where commandCount
 is different from argumentCount, namely
 engines/mohawk/riven_stacks/aspit.cpp:377, so it is not that surprising
 that this is the only place where the problem occurs.

 By the way, there is some commented out code in
 engines/mohawk/riven_stacks/jspit.cpp:312 that perhaps would work after
 the fix.
-- 
Ticket URL: <https://bugs.scummvm.org/ticket/13416#comment:7>
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