Category : C++ Source Code
Archive   : VCCRT2.ZIP
Filename : XCHKSTK0.ASM

page ,132
title chkstk - C stack checking routine
;***
;chkstk.asm - C stack checking routine
;
; Copyright (c) 1985-1992 Microsoft Corporation, All Rights Reserved
;
;Purpose:
; Provides support for automatic stack checking in C procedures
; when stack checking is enabled.
;
;*******************************************************************************

.xlist
?PLM=0
?WIN=0

ifdef MI_NEAR
memS equ 1 ; near version
_chkstk equ <_aNchkstk>
ifdef mem_m ; if the default memory model is
USE_EXTERNS equ 1 ; medium or large, then use externs
endif ; in this module
ifdef mem_l
USE_EXTERNS equ 1
endif

elseifdef MI_FAR
memM equ 1 ; far version
_chkstk equ <_aFchkstk>
ifdef mem_s ; if the default memory model is
USE_EXTERNS equ 1 ; small or compact, then use externs
endif ; in this module
ifdef mem_c
USE_EXTERNS equ 1
endif

else
include version.inc ; default version
endif

include cmacros.inc
include msdos.inc

.list

sBegin data
assumes ds,data


extrn __end:word ; stack bottom

ifdef USE_EXTERNS

if sizeC
externCP _aaltstkovr ; alternate stack overflow
endif

extrn _STKHQQ:word

else ;not USE_EXTERNS
if sizeC
globalCP _aaltstkovr,-1 ; alternate stack overflow
endif

public _STKHQQ ; used by parasitic heap
_STKHQQ dw dataoffset __end+STACKSLOP ; initial value
endif ;not USE_EXTERNS

sEnd data


sBegin code
assumes ds,data
assumes cs,code

externNP _amsg_exit ; write error and die

page
;***
;_chkstk - check stack upon procedure entry
;
;Purpose:
; Provide stack checking on procedure entry.
;
;Entry:
; AX = size of local frame
;
;Exit:
; SP = new stackframe if successful
;
;Uses:
; AX, BX, CX, DX
;
;Exceptions:
; Gives out of memory error and aborts if there is not enough
; stack space for the routine.
; MTHREAD version also gives that error if the Thread ID is out of range
;
;*******************************************************************************

% labelP

if sizeC
pop cx ; get return offset
pop dx ; get return segment
else
pop cx ; get return offset
endif

mov bx,sp

ifdef _LOAD_DGROUP
push ds
push DGROUP
pop ds
endif ;_LOAD_DGROUP

sub bx,ax ; new position
jc OMerr ; error - out of memory

cmp bx,[_STKHQQ] ; SP - AX : _STKHQQ (for heap/stack)
jb OMerr ; error - out of memory

mov sp,bx ; set new stack pointer


ifdef _LOAD_DGROUP
mov bx, es ; restore ds Note: If an error occurs it
mov ds, bx ; is assumed that ds does not have to be
endif ;_LOAD_DGROUP ; restored since the program ends.


if sizeC
push dx ; push segment
push cx ; push offset
chkproc proc far
ret ; far return to dx:cx
chkproc endp
else
jmp cx ; return to cx
endif

OMerr:
if sizeC
push dx ; user segment
endif
push cx ; user offset

if sizeC
mov ax,word ptr [_aaltstkovr]
inc ax
jnz altstkovr
endif
xor ax,ax
jmp _amsg_exit ; give stack overflow and die

if sizeC
altstkovr:
jmp [_aaltstkovr] ; Pascal/FORTRAN stack overflow
endif

sEnd code

end