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https://github.com/cc65/cc65.git
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0ee9b2e446
So far the INIT segment was run from the later heap+stack. Now the INIT segment is run from the later BSS. The background is that so far the INIT segment was pretty small (from $80 to $180 bytes). But upcoming changes will increase the INIT segment in certain scenarios up to ~ $1000 bytes. So programs with very limited heap+stack might just not been able to move the INIT segment to its run location. But moving the INIT segment to the later BSS allows it to occupy the later BSS+heap+stack. In order to allow that the constructors are _NOT_ allowed anymore to access the BSS. Rather they must use the DATA segment or the new INITBSS segment. The latter isn't cleared at any point so the constructors may use it to expose values to the main program. However they must make sure to always write the values as they are not pre-initialized.
107 lines
2.4 KiB
ArmAsm
107 lines
2.4 KiB
ArmAsm
;
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; Startup code for cc65 (PET version)
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;
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.export _exit
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.export __STARTUP__ : absolute = 1 ; Mark as startup
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.import initlib, donelib
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.import zerobss, push0
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.import callmain
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.import CLRCH, BSOUT
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.importzp ST
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.include "zeropage.inc"
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.include "pet.inc"
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.include "../cbm/cbm.inc"
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; ------------------------------------------------------------------------
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; Startup code
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.segment "STARTUP"
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Start:
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; Save the zero-page locations that we need.
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ldx #zpspace-1
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L1: lda sp,x
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sta zpsave,x
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dex
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bpl L1
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; Switch to the second charset. The routine that is called by BSOUT to switch the
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; character set will use FNLEN as temporary storage -- YUCK! Since the
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; initmainargs routine, which parses the command line for arguments, needs that
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; information, we need to save and restore it here.
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; Thanks to Stefan Haubenthal for this information!
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lda FNLEN
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pha ; Save FNLEN
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lda #14
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; sta $E84C ; See PET FAQ
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jsr BSOUT
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pla
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sta FNLEN ; Restore FNLEN
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; Clear the BSS data.
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jsr zerobss
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; Save some system stuff; and, set up the stack.
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tsx
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stx spsave ; Save the system stack ptr
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lda MEMSIZE
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sta sp
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lda MEMSIZE+1
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sta sp+1 ; Set argument stack ptr
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; Call the module constructors.
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jsr initlib
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; Push the command-line arguments; and, call main().
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jsr callmain
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; Call the module destructors. This is also the exit() entry.
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_exit: pha ; Save the return code on stack
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jsr donelib
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; Copy back the zero-page stuff.
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ldx #zpspace-1
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L2: lda zpsave,x
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sta sp,x
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dex
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bpl L2
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; Store the program return code into BASIC's status variable.
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pla
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sta ST
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; Restore the stack pointer.
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ldx spsave
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txs ; Restore stack pointer
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; Back to BASIC.
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rts
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; ------------------------------------------------------------------------
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.segment "INITBSS"
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zpsave: .res zpspace
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; ------------------------------------------------------------------------
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.bss
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spsave: .res 1
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mmusave:.res 1
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