Print Page - Access Violation with a global variable inside WndProc

Title: Access Violation with a global variable inside WndProc
Post by: xandaz on December 19, 2016, 12:33:55 PM

Hi guys. Long time no see. I'm trying to get back on track. The problem is of the sort:

.data
hToolbar  HWND ?
...
.code
...
WndProc...
...
    mov hToolbar,eax ( this right after CreateWndowEx )

olly says access violation.
works with local variables.
thanks

Title: Re: Access Violation with a global variable inside WndProc
Post by: jj2007 on December 19, 2016, 07:23:52 PM

Aggressive linker settings?

Using /MERGE:.data=.text, this one works with polink but with M$ link it crashes:

include \masm32\include\masm32rt.inc

.data
global	dd ?

.code
start:
  mov global, eax
  print "ok"
  exit
end start

Title: Re: Access Violation with a global variable inside WndProc
Post by: BugCatcher on December 22, 2016, 02:16:53 AM

Doesn't uninitialized data (?) have to be in a unitialized data section .data?

Title: Re: Access Violation with a global variable inside WndProc
Post by: hutch-- on December 22, 2016, 04:48:11 AM

Try this.


.data?        ; <<<< UNinitialised data section.
hToolbar  HWND ?

Title: Re: Access Violation with a global variable inside WndProc
Post by: jj2007 on December 22, 2016, 06:19:14 AM

Quote from: BugCatcher on December 22, 2016, 02:16:53 AM
Doesn't uninitialized data (?) have to be in a unitialized data section .data?

In can be in data?, but it doesn't have to. You increase your exe size by 4 bytes, but that's the only disadvantage.

Title: Re: Access Violation with a global variable inside WndProc
Post by: xandaz on December 23, 2016, 10:41:26 AM

Really? I thought the question mark didn't matter... let me see. Thanks guys

Title: Re: Access Violation with a global variable inside WndProc
Post by: xandaz on December 23, 2016, 10:43:37 AM

Not working... this never happened. Could it be one of those stupid things? I have a lot of that. Skipping the obvious details is my speciallty. ty

Title: Re: Access Violation with a global variable inside WndProc
Post by: xandaz on December 23, 2016, 11:10:23 AM

Solved. Using WSTR instead of UCSTR. Forgot to mention it has been a problem before. ty

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