bryce@hoser.berkeley.edu (Bryce Nesbitt) (12/29/87)
/*
----------------------------------------------------------------------------
Technical Note #4
Stack, how to determine size at run time
SUMMARY
$ 4/0 Stack, how to determine size at run time
$ release
$ 26-Dec-87 Bryce Nesbitt / BDI
$ stack, Workbench, CLI, process, startup
It should be straightforward to determine the size of the stack your
program is running on. Sadly it is not. This note should clear the
confusion.
----------------------------------------------------------------------------
If your program needs more than the 4000 byte default stack, it has
some work to do. It will need to check if the stack is large enough
for it's needs and take one of two actions if it is not:
1. Abort with an error requester.
2. Allocate enough space and (using assembly language) point the stack
pointer to it.
LANGUAGES
Some languages will provide a global that you can look at to
determine the size of the current stack. This is cleanest option, if
it is available to you.
If there is any chance at all that user input may cause your
program to use more stack than normal, leave the stack checking option
of your compiler enabled. Recursive functions are particularly
notorious stack blowers.
WORKBENCH
When stared from the Workbench tool, your stack size might have
come from one of three places:
1. The stack field of a Project icon.
2. The stack field in your Tool's icon.
3. The Workbench's default stack size.
The icon that started you tool decides the stack size. If the
stack field is blank, then the default of ~4000 bytes is used. The
size is recorded in the normal task structures.
If the user sets the stack size to an odd number then the Workbench
tool will crash, so don't worry about that situation.
CLI
When your code is started up it does NOT get a new process
invocation; as "CLI 3" your code is literally the same process that
runs CLI task 3.
When the CLI starts up a program it allocates a brand new stack.
This is *not* the same stack the CLI itself uses. The size of this
stack is *not* recorded in the normal "task" structure; it must be
extracted from the top of the stack at startup or from the
"cli_DefaultStack" field.
;-------------- ASSEMBLY EXAMPLE -----------
;
; 25-Jan-87 Bryce Nesbitt
;
; A complete startup module for assembly language programs. Works from
; Workbench or CLI.
;
NOLIST
INCLUDE "exec/types.i"
INCLUDE "libraries/dosextens.i"
LIST
jsrlib MACRO
xref _LVO\1
jsr _LVO\1(a6)
ENDM
;
; On startup (A7) contains a return address,
; 4(A7) contains the size of the stack in bytes
;
move.l 4(a7),d7 ;--Get CLI stack size--
move.l 4,a6 ;Get exec library pointer
suba.l a1,a1 ;Put zero in A1
jsrlib FindTask ;Find this task
move.l d0,a5
moveq #0,d0 ;Set zero for later
move.l pr_CLI(a5),d1 ;Check CLI/Workbench flag
bne.s fromCLI
move.l pr_StackSize(a5),d7 ;--Get Workbench stack size--
lea.l pr_MsgPort(a5),a0 ;Wait for the message
jsrlib WaitPort ; the Workbench will send
lea.l pr_MsgPort(a5),a0
jsrlib GetMsg
fromCLI move.l d0,-(a7) ;Save the message, or zero
****************************************** A5-This task D7-Stack size
;...your code here...
****************************************** D7-MUST contain result code
ExitToDOS: move.l (a7)+,d2
beq.s notWorkbench
jsrlib Forbid ;Required so we won't be unloaded by
move.l d2,a1 ; the Workbench too soon.
jsrlib ReplyMsg ;Reply to the Workbench message
notWorkbench move.l d7,d0 ;Return result code:
rts ; 0 = ok 10 = error
END ; 5 = warning 20 = severe failure
----------------- C EXAMPLE ----------------
*/
/*
* stack_test.c 27-Oct-87. Bryce Nesbitt
*
*/
#include "exec/types.h"
#include "exec/tasks.h"
#include "libraries/dosextens.h"
#include "stdio.h"
struct Process *FindTask();
void main()
{
register struct Process *Process;
register FILE *Handle;
struct CommandLineInterface *CLI;
if (!(Handle=fopen("con:0/11/250/128/Stack Window","a")))
exit(20); /* "a" is used so the window won't flicker */
Process=FindTask(0L);
if (CLI=(struct CommandLineInterface *)(Process->pr_CLI<<2))
{
if (CLI->cli_Background)
fprintf(Handle,"Background");
else
fprintf(Handle,"Foreground");
fprintf(Handle," CLI #%ld\n",Process->pr_TaskNum);
fprintf(Handle,"Actual stack is: %ld\n\n",
CLI->cli_DefaultStack<<2);
}
else
{
fprintf(Handle,"This is not a CLI process\n");
fprintf(Handle,"Actual stack is %ld\n\n",Process->pr_StackSize);
}
/* Other useless information (we already know the stack size) */
fprintf(Handle,"pr_StackSize %ld\n",Process->pr_StackSize);
fprintf(Handle,"pr_StackBase $%lx\n\n",Process->pr_StackBase<<2);
fprintf(Handle,"tc_SPLower $%lx\n",Process->pr_Task.tc_SPLower);
fprintf(Handle,"tc_SPUpper $%lx\n",Process->pr_Task.tc_SPUpper);
fprintf(Handle,"Upper-Lower %ld\n\n",
(long)Process->pr_Task.tc_SPUpper-
(long)Process->pr_Task.tc_SPLower);
fprintf(Handle,"tc_SPReg $%lx\n",Process->pr_Task.tc_SPReg);
Delay(80L); /* Be quick :-). BTW: *Never* Delay(0L);! */
fprintf(Handle,"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n");
/* Dramatic exit :-) */
fclose(Handle);
}
|\ /| . Ack! (NAK, SOH, EOT)
{o O} . bryce@hoser.berkeley.EDU -or- ucbvax!hoser!bryce (or try "cogsci")
(")
U "Your theory is crazy... but not crazy enought to be true." -Niels Bohrclaudio@forty2.UUCP (Claudio Nieder) (01/12/88)
In article <22330@ucbvax.BERKELEY.EDU> bryce@hoser.berkeley.edu (Bryce Nesbitt) writes: > The icon that started you tool decides the stack size. If the > stack field is blank, then the default of ~4000 bytes is used. The > size is recorded in the normal task structures. I suggest the following improvment for 1.3: Instead of takeing the stack size from the icon that was double-clicked, the largest stacksize of all icons should be taken. claudio