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Old 01 December 2017, 23:03   #1
dalton
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Join Date: Jun 2006
Location: Gothenburg / Sweden
Posts: 71
vbcc bss clearing issue

I've been having some trouble with constant data included in my program being cleared already before my program starts running.

So I disassembled to linked executable of my program, and found this piece of code just 5 rows into the program. It is a loop which iterates 0x30 (48) times. Each time clearing one longword.
Code:
	MOVE.L	#$00000030,D0
	BEQ.S	LAB_0002
	LEA	__BSSBAS,A0
LAB_0001:
	CLR.L	(A0)+
	SUBQ.L	#1,D0
	BNE.S	LAB_0001
LAB_0002:
Further down the source is the __BSSBAS declaration:

Code:
	SECTION S_2,DATA

SECSTRT_2:
	DC.L	$00220063,$41000000
__BSSBAS:
	DS.L	1
_SysBase:
	DS.L	1
_DOSBase:
	DS.L	1
_WBenchMsg:
	DS.L	1
__WBenchMsg:
	DS.L	1
__stdin:
	DS.L	1
__stdout:
	DS.L	1
__stderr:
	DS.L	1
_errno:
	DS.L	1
___stack_usage:
	DS.L	1
___stackLower:
	DS.L	1
___stackPtr:
	DS.L	1


	SECTION S_3,DATA

SECSTRT_3:
	DS.L	1
_GfxBase:
	DS.L	1
There are 12 longwords from __BSSBAS to the end of the section, ie 48 (0x30) bytes.

The clearing loop in the beginning of the program appears to be clearing 4 times the data it should. So it basically goes on to clear some constant data I have included in my program.

Very strange! Is it a bug in vbcc?

VBCC 0.9e
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