Path: utzoo!utgpu!attcan!uunet!husc6!mailrus!cornell!uw-beaver!fluke!ssc-vax!uvicctr!tholm
From: tholm@uvicctr.UUCP (Terrence W. Holm)
Newsgroups: comp.os.minix
Subject: alloca(3) for MINIX-ST
Message-ID: <547@uvicctr.UUCP>
Date: 8 Nov 88 22:39:51 GMT
Reply-To: tholm@uvicctr.UUCP (Terrence W. Holm)
Organization: University of Victoria, Victoria B.C. Canada
Lines: 130

EFTH MINIX report #57  - November 1988 -  alloca(3) for MINIX-ST


There follows an implementation of alloca(3) for MINIX-ST.
The code is directly derived from Peter S. Housel's
alloca(3) for MINIX-XT.

"man" pages are included.


----------------------------------------------------------
echo x - alloca.3
gres '^X' '' > alloca.3 << '/'
XSUBROUTINES
X    alloca(3)		- allocate space on the stack
X
XINVOCATION
X    char *alloca( size )
X      unsigned size;
X
XEXPLANATION
X    Alloca(3) allocates <size> bytes on the stack. Blocks
X    allocated within a stack frame are released on exit
X    from the current subroutine.
X
XRESULTS
X    o/w  : Pointer to allocated memory.
X    NULL : No room for block.
X
XREFERENCES
X    chmem(1), malloc(3)
/
echo x - free.3
gres '^X' '' > free.3 << '/'
XSUBROUTINES
X    free(3)		- release allocated memory
X
XINVOCATION
X    free( p )
X      char *p;
X
XEXPLANATION
X    Free(3) releases a block previously allocated by malloc(3),
X    realloc(3) or calloc(3).
X
XREFERENCES
X    malloc(3)
/
echo x - malloc.3
gres '^X' '' > malloc.3 << '/'
XSUBROUTINES
X    malloc(3)		- memory allocation routines
X
XINVOCATION
X    char *malloc( size )
X      unsigned size;
X
X    char *realloc( old, size )
X      char *old;
X      unsigned size;
X
X    char *calloc( n, size )
X      unsigned n;
X      unsigned size;
X
XEXPLANATION
X    These routines allocate blocks of memory above the
X    process' bss section. Malloc(3) requests <size> bytes.
X    Realloc(3) requests a change in an <old> block's
X    allocation to <size>. Calloc(3) allocates <n> times
X    <size> bytes, and then clears the memory before returning.
X
XRESULTS
X    o/w  : Pointer to allocated memory.
X    NULL : No room for block. For realloc(3), <old> is not
X           released.
X
XREFERENCES
X    chmem(1), brk(2), alloca(3), free(3)
/
echo x - alloca.s
gres '^X' '' > alloca.s << '/'
X	.define	_alloca
X	.sect	text
X!
X! alloca() for Minix
X! by Peter S. Housel 8/15/88 - in the public domain
X!
X! Changed for 68000 - Terrence W. Holm  &
X!		    - Frans Meulenbroeks  - Nov. 1988
X!
X! Stack frame:
X!    on entry			on return
X!    |	...	 |		| ...	    |
X!    |-----------| <=caller sp	|-----------|
X!    | size arg  |		|	    |
X!    |-----------|		|alloca data|
X!    | ret addr  |		| ...	    |
X!    |-----------| <=sp		|-----------| <= return value in d0
X!				| dummy word|
X!				|-----------| <= sp
X!
X	.globl _alloca
X	.globl _brksize
X_alloca:
X	move.l	(a7),a0		! save return address
X	move.l	a7,d0
X	add.l	#6,d0		! d0 = sp from calling routine
X	clr.l	d1
X	move.w	4(a7),d1
X	sub.l	d1,d0		! d0 = beginning of alloca block
X	and.b	#0xfc,d0	! round to long address
X	move.l	_brksize,d1
X	add.l	#40,d1		! ensure space below new sp
X	cmp.l	d1,d0
X	ble	fail
X	move.l	d0,a7		! set new sp
X	sub.l	#2,a7		! push a dummy value for caller to remove
X	jmp	(a0)		! jump back to caller
Xfail:
X	clr.l	d0		! return NULL pointer
X	rts
/
----------------------------------------------------------

		Frans Meulenbroeks
		  uunet!mcvax!philmds!prle!cst!meulenbr

		Terrence W. Holm
		  uw-beaver!uvicctr!tholm