Conversation

Chetan Nayak (Brute Ratel C4 Author)

@NinjaParanoid

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Jan 26

Maybe you should read some msdn docs instead of arrogantly shouting what you dont understand

learn.microsoft.com

_chkstk Routine - Win32 apps

Called by the compiler when you have more than one page of local variables in your function.

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Chetan Nayak (Brute Ratel C4 Author)

@NinjaParanoid

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Jan 26

More RTFM for you "_chkstk() increases the stack when needed by committing some of the pages previously reserved for the stack. If there is no more physical memory available for committed pages, _chkstk fails"

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Chetan Nayak (Brute Ratel C4 Author)

@NinjaParanoid

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Jan 26

"When you enter a function (VC++ with the stack checking enabled), it will call the _chkstk located in CHKSTK.ASM. This function does a stack page probing and causes the necessary pages of memory to be allocated using the guard page scheme, if possible."

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namazso

@namazso

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Jan 26

Nowhere in these three quotes does it say it catches anything. "increases the stack", "causes the necessary pages of memory to be allocated". That is because it does not catch anything. It causes exceptions that are caught and memory allocated in place of the guard pages.

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namazso

@namazso

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Jan 26

So while your supposedly source materials are correct, you interpreted it wrong, and your statement ("This exception is usually caught by the _chkstk routine") is simply just wrong. Nothing in those links and quotes says anything equivalent to that.

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namazso

@namazso

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Jan 26

In case you're wondering where the magic *actually* happens, check nt!MiCheckForUserStackOverflow

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Chetan Nayak (Brute Ratel C4 Author)

@NinjaParanoid

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Jan 27

The doc literally says "_chkstk() increases the stack when needed by committing some of the pages previously reserved for the stack". How did you miss that?

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namazso

@namazso

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Jan 27

That is not what your article states. It states that _chkstk catches exceptions. Can you provide a source to that?

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Chetan Nayak (Brute Ratel C4 Author)

@NinjaParanoid

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Jan 27

I did provide a source in the other tweet reply, but here it is again. You will find a lot more in stackoverflow if you simply google it.

codeguru.com

Adventures with _chkstk | CodeGuru

_chkstk Routine is a helper routine for the C compiler. For x86 compilers, _chkstk Routine is called when the local variables exceed 4K bytes; for x64

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Chetan Nayak (Brute Ratel C4 Author)

@NinjaParanoid

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Jan 27

This, again!

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namazso

@namazso

That literally does not say _chkstk catches exceptions. At this point I feel like talking to a wall. You're reposting the same link that simply does not support what you're saying.

9:20 AM · Jan 27, 2023

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Chetan Nayak (Brute Ratel C4 Author)

@NinjaParanoid

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Jan 27

You are just being arrogant without reading anything. The _chkstk probes and allocates memory, The __chkstk just probes. You said it yourself _chkstk does not allocate memory. Go back and read your own tweets. PFA msdn git source code

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namazso

@namazso

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Jan 27

And this is related to your incorrect statement about catching exceptions how exactly?

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