Introducing: Nintendo Coding!


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Main - NSMB2 hacking - Introducing: Nintendo Coding!

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shibboleet

Posted on 10-23-16 03:39 AM (rev. 5 of 10-23-16 01:21 PM)

Link | #79056

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I've presented "dumb assembly" code before, but turns out it actually had a use.

here, no. not even close. It sets up the stack and shit, which is pretty much any function. but what's in the function is what's stupid.

If moves 1 into r0. Okay, normal. But now, it compares r0 to 1. Then if it isn't equal, it makes it 1. If you're confused, here's the C++ code for it:

void StupidFunction1()
{
    r0 = 1;
    
    if (r0 != 1)
    {
        r0 = 1; // this is never ran
    }
}

And here's the actual function in assembly:

RAM:004573BC StupidFunction1                         ; CODE XREF: sub_47EB10+4p
RAM:004573BC                 STMFD   SP!, {R4,LR}
RAM:004573C0                 MOV     R0, #1
RAM:004573C4                 CMP     R0, #0
RAM:004573C8                 MOVNE   R0, #1
RAM:004573CC                 LDMFD   SP!, {R4,PC}
RAM:004573CC
RAM:004573CC ; End of function StupidFunction1

oh look, another one!

void someFunction(u32 shit)
{
	if (shit != 0)
	{
		shit = 1;
	}
}

RAM:0047EB10 StupidFunction2                         ; DATA XREF: RAM:00599590o
RAM:0047EB10                                         ; RAM:005A3C1Co
RAM:0047EB10                                         ; RAM:005A7600o
RAM:0047EB10                                         ; RAM:005C5ABCo
RAM:0047EB10                 STMFD   SP!, {R4,LR}
RAM:0047EB14                 BL      StupidFunction1
RAM:0047EB14
RAM:0047EB18                 CMP     R0, #0
RAM:0047EB1C                 MOVNE   R0, #1
RAM:0047EB20                 LDMFD   SP!, {R4,PC}
RAM:0047EB20
RAM:0047EB20 ; End of function StupidFunction2

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Arisotura

Posted on 10-23-16 12:32 PM (rev. 2 of 10-23-16 12:34 PM)

Link | #79067

Star Mario
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There are a ton of those examples in their code. We should collect them and put them up somewhere. It's like they don't know how to configure a compiler.

Anyway, the second example is wrong.

if (shit != 0) shit = 1;

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zafkflzdasd

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(post deleted)

#79068

Arisotura

Posted on 10-23-16 12:37 PM (rev. 2 of 10-23-16 12:38 PM)

Link | #79069

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~~Compiled code doesn't include function or variable names. Those names were entered in IDA.~~ -- line irrelevant because derpster deleted his post

Also, I didn't notice that StupidFunction2 calls StupidFunction1. A decent optimization pass would eliminate the call entirely and just return 1 directly. Less smart optimization would leave the call but atleast make StupidFunction1 return 1 directly. This is like they, uh, applied no optimization at all.

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MC708

Posted on 10-23-16 12:40 PM (rev. 3 of 10-23-16 12:44 PM)

Link | #79072

Cheep-cheep
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Wait, so if I'm correct, they changed a variable (or whatever it is after its compiled) to 1, and then checked if its 1? But it's guaranteed to be 1! What a waste of data...

Just like EnCryptiX.

Also I deleted the post because it was a stupid question, I realised that Nintendo wouldn't randomly call it stupid in their code.

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shibboleet

Posted on 10-23-16 01:23 PM (rev. 2 of 10-23-16 01:23 PM)

Link | #79074

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i literally explain it in the first post.

also, you don't get assigned "variables", just whatever the coder names it gets trashed. The only things that are kept through a compiler are symbols

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MC708

Posted on 10-23-16 01:24 PM

Link | #79075

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Posted by MrRean
i literally explain it in the first post.

I was just checking if I had correctly understood what you said in your first post, sorry

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RicBent

Posted on 10-23-16 03:56 PM

Link | #79079

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CMP        R0, #0
MOVEQ      R0, #0

yea, this surely does a lot.

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Main - NSMB2 hacking - Introducing: Nintendo Coding!

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