[sdcc-devel] [ sdcc-Bugs-840148 ] unsafe interrupt handlers

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Bugs item #840148, was opened at 2003-11-11 12:14
Message generated for change (Comment added) made by epetrich
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Category: msc51(8051) target
>Group: fixed
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Stas Sergeev (stsp)
>Assigned to: Erik Petrich (epetrich)
Summary: unsafe interrupt handlers

Initial Comment:
Hi.

It seems sdcc has a bug and forgets to generate a
registers save/restore code for the interrupt handlers.
Looking in the sdcc sources, the logic looks simple:
save/restore the regs only if the inthandler calls
another function, otherwise save only the registers
it uses itself.
Unfortunately there is a miss somewhere, and if the
inthandler calls another function, the registers are
not being saved/restored:(
The example that demonstrates the problem, is
attached.
Here is how the generated asm look like:

---
;intr.c:9: void timer() interrupt 1
;	-----------------------------------------
;	 function timer
;	-----------------------------------------
_timer:
	push	acc
	push	b
	push	dpl
	push	dph
	push	ar2
	push	psw
	mov	psw,#0x00
;intr.c:11: timer_expired++;
[very few regs are saved]
[skip]
00107$:
;intr.c:13: test_func();
;     genCall
	lcall	_test_func
[function call that corrupts the rest of the regs]
00103$:
---

Adding a hack to gen.c to work-around that problem
was easy, but that yelded a great success! All the
random crashes I had are gone and some programs are
finally, for the first time I am trying sdcc, are
running properly (not all of them yet, but getting
there).
You have a very nice compiller guys, and you are
doing a great work, keep it that way!
(just my 2 pences:)

----------------------------------------------------------------------

>Comment By: Erik Petrich (epetrich)
Date: 2003-11-12 02:44

Message:
Logged In: YES 
user_id=635249

It's already supposed to save _all_ the registers if any
function call is found. However, in certain circumstances
(the function call immediately preceeded a control flow
merge point) a bug caused the function call to be unnoticed.
Fixed in src/SDCCBBlock.c 1.31

----------------------------------------------------------------------

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