I've found that erratic behaviour of my program is caused by overlay of local data/bit variables from subroutines called from main and variables of subroutines called from interrupt service routines. I am using Rkit51 w. LX51 with default options.

I would expect that LX51 assumes that interrupt routine (and its subroutines) can be called from main (and its every subroutine) automatically.

Example:
SEGMENT BI_GROUP DT_GROUP ID_GROUP XD_GROUP
+--> CALLED SEGMENT START LENGTH START LENGTH START LENGTH START LENGTH
--------------------------------------------------------------------------------------

?PR?Ext0Int?MAIN?S?MAIN 0023H.0 0000H.1 0067H 0001H ------------- -----------------
+--> ?PR?_Burst_LUT_process?BURST

?PR?_Burst_LUT_process?BURST 0022H.4 0000H.1 003EH 0001H --------------- 87F1H 000EH
+--> ?PR?_idee_semilog_enc?BURST

?PR?_idee_semilog_enc?BURST --------------- 003FH 0005H --------------- ---------------

?PR?main?MAIN 0022H.1 0000H.1 0024H 0009H 001EH 0002H 872AH 0003H
+--> ?PR?_GetHSKa?ADC_UTILS

?PR?_GetHSKa?ADC_UTILS 0022H.2 0000H.2 0032H 0002H --------------- ---------------
+--> ?PR?_ReadADCint?ADC_UTILS

?PR?_ReadADCint?ADC_UTILS 0022H.4 0000H.4 003EH 0007H --------------- ---------------

Morover, I cannot add ?PR?Ext0Int?MAIN?S?MAIN to the LX51 OVERLAY directive to tell the linker there is a potential call.
LX51 returns error