[sdcc-devel]CVS from april 16th does not produce reliable 8051 code

[Michael S. <msc...@ba...>]

Hi sdcc fellows,

after a being busy with my broken thumb for a couple of weeks i am back
on the list again.

i was lucky able to compile sdcc again with the sources from april
16th.  my last build was Jan. 29

1. good thing. the lastest build is very fast in execution. dramatically
faster !!! yes ...
2. bad news

it seems that there are a couple of strange problems with the resulting
code. compiling it with version jan29 the code works fine. but with the
current it does not. the projekt is too big to post it here and too much
hw dependend, lots of ints ... statemachines ...

i would like to help to find out what the problem with the current cvs
version is. but i think i need a bit of advice what information i can
give to you all.

i compile the whole projekt with 
--stack-after-data  --model-small --iram-size 256 --xram-loc 0xF400
--int-long-reent --compile-only
also tried out the large model but no difference.

strange behavior in both versions is, that it is getting more worse if i
put the variables used in interrupts in idata except xdata.

second, the following code does not wotk properly when using signed und
unsigned

xdata unsigned char ReceiveDataChar[8];
#define KonfigurationMinTemperatur	-10
#define KonfigurationMaxTemperatur	+60

if(
     ((signed char)ReceiveDataChar[0] <  (signed
char)ReceiveDataChar[1]) // This line does not work if negative values
are used
&&
     ((signed char)ReceiveDataChar[0] >= (signed
char)KonfigurationMinTemperatur) // This line works
&&
     ((signed char)ReceiveDataChar[1] <= (signed
char)KonfigurationMaxTemperatur) // This line works too
  )

the problem here is that ReceiveDataChar[0] can be negative (-5) and
ReceiveDataChar[1] positive (+50) and in this case the first line
((signed char)ReceiveDataChar[0] <  (signed char)ReceiveDataChar[1])
guesse 0xFB(=-5) < 0x32(=+50) is false. even when using typecasting.
this is the fact for all sdcc builds i have here. 



-- 
Dipl.-Ing. (FH) Michael Schmitt
Baumer Ident GmbH
Entwicklung / Development Department
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