Auto Assembler:TRY EXCEPT - Revision history

Gusito: Added note about position

2022-10-14T17:35:52Z

Added note about position

Csimbi: Added remark on {$try} being a label

2019-07-25T16:58:07Z

Added remark on {$try} being a label

Dark Byte: cleaner

2018-12-09T09:54:39Z

cleaner

Csimbi at 21:35, 17 November 2018

2018-11-17T21:35:42Z

Csimbi at 21:29, 17 November 2018

2018-11-17T21:29:09Z

Csimbi at 21:28, 17 November 2018

2018-11-17T21:28:49Z

Csimbi: First draft

2018-11-17T21:27:34Z

First draft

New page

CE 6.8 added {$try}/{$except} to auto assembler scripts.

Essentially, any code included in the {$try}/{$except} block will jump to the {$EXCEPT} part when any kind of exception happens within the block.

This means, you will want to put the code likely to result in an error between {$try} and {$except}.

Next, at the end of {$try} you will want to force a jump to a location indicating success; if you do not, then the code after {$except} will be executed.

Also note that the exception may break from any line, so make sure that you exception code can handle unexpected register values.

In this example, if any error occurs - for example, ecx is zero or ecx+10 is unreadable -, eax will be set to zero:

{$try}

mov eax,[ecx+10]

jmp short @f

{$except}

xor eax,eax

@@:

@@ Line 32: / Line 32: @@
 Remarks:
 {$try} is actually a label.
 Meaning, you should not use anonymous labels (i.e. @@) with forward (@f) and backwards (@b) that are supposed to jump over the {$try}/{$except} block because the @f and @b will jump to the {$try} label rather your intended anonymous label.

← Older revision		Revision as of 16:58, 25 July 2019
Line 29:		Line 29:

	- There should be hardly any performance hit as long as no exception happens.		- There should be hardly any performance hit as long as no exception happens.
		+
		+
		+	Remarks:
		+	{$try} is actually a label.
		+	Meaning, you should not use anonymous labels (i.e. @@) with forward (@f) and backwards (@b) that are supposed to jump over the {$try}/{$except} block because the @f and @b will jump to the {$try} label rather your intended anonymous label.

@@ Line 18: / Line 18: @@
 mov eax,[ecx+10]
-jmp short @f
+jmp short noerror
 {$except}
@@ Line 24: / Line 24: @@
 xor eax,eax
-@@:
+noerror:
 Benefits:
 - There should be hardly any performance hit as long as no exception happens.

← Older revision		Revision as of 21:35, 17 November 2018
Line 9:		Line 9:
	Also note that the exception may break from any line in the {$try}/{$except} block, so make sure that your exception code can handle unexpected register values.		Also note that the exception may break from any line in the {$try}/{$except} block, so make sure that your exception code can handle unexpected register values.

		+	How does it work? It works by assembling an exception handler in the game and then register it using addvectoredexception handler. Then, it adds a list of eip/rip ranges and where to jump to on exception. So, when an exception happens it checks if it's in the list, and if so, change eip/rip to the exception address.


Line 24:		Line 25:

	@@:		@@:
		+
		+	Benefits:
		+
		+	- There should be hardly any performance hit as long as no exception happens.

← Older revision		Revision as of 21:29, 17 November 2018
Line 7:		Line 7:
	Next, at the end of {$try} you will want to force a jump to a location indicating success; if you do not, then the code after {$except} will be executed.		Next, at the end of {$try} you will want to force a jump to a location indicating success; if you do not, then the code after {$except} will be executed.

−	Also note that the exception may break from any line in the {$try}/{$except} block, so make sure that ~~you~~ exception code can handle unexpected register values.	+	Also note that the exception may break from any line in the {$try}/{$except} block, so make sure that your exception code can handle unexpected register values.

← Older revision		Revision as of 21:28, 17 November 2018
Line 7:		Line 7:
	Next, at the end of {$try} you will want to force a jump to a location indicating success; if you do not, then the code after {$except} will be executed.		Next, at the end of {$try} you will want to force a jump to a location indicating success; if you do not, then the code after {$except} will be executed.

−	Also note that the exception may break from any line, so make sure that you exception code can handle unexpected register values.	+	Also note that the exception may break from any line in the {$try}/{$except} block, so make sure that you exception code can handle unexpected register values.