1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
/* Copyright (C) 1995,1996 Robert de Bath <rdebath@cix.compulink.co.uk>
* This file is part of the Linux-8086 C library and is distributed
* under the GNU Library General Public License.
*/
/* Alloca is a nice interesting function */
/* Needs change to BCC to work, as BCC doesn't use 'mov sp,bp:pop bp' */
/* The only other way to do it is to use malloc and the emacs alloca */
#if 0
THIS IS BROKEN!!!
#asm
export _alloca
.text
_alloca:
pop cx ! The program counter
pop ax ! The argument (>1 arg == snafu)
inc ax
and al,$FE ! Round up to even
test ax,ax
jz too_big ! Well _I_ think it means 64k ! :-) (ANSI too IIUC)
mov bx,sp
sub bx,ax ! Calc new SP
jb too_big ! SP wrapped, snafu!
mov ax,[brk_addr]
add ax,#64 ! Check if brk has allocated the memory first but
cmp bx,ax ! leave a little bit of space before we collide!
jb too_big
xchg bx,sp ! Put it in place, may need the old SP for other args
mov ax,sp ! The bottom of the area allocated
! This is needed if si/di popped before mov sp,bp
!push [bx+4] ! This copies the saved register vars and possibly a temp
!push [bx+2] ! value, beware snafu if called within complex expression!
!push [bx] !
push ax ! Anything really, it will be deallocated by the caller
jmp cx ! Return
too_big:
xor ax,ax ! Sorry not enough stack
push ax ! More junk
jmp cx ! Return
#endasm
#endif
|
