*pragmapush list
                *pragma list
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; The error handler
;
; Enter with the error number in B. This routine will do some cleanup and handle any ON ERROR GOTO handler that
; may be active.
;
; Note the error message lookup does not need to be efficient which is why the lookup just runs through the list
; of error messages in sequence looking for NUL terminators. The specific handling of B (error number) below avoids
; issues if there happen to be error codes above 128.
ERROR           clr filenum                     ; reset display device to console
                jsr writecondnl                 ; do a newline if needed (will preserve B)
                bsr ERRORstr                    ; get the error message string
ERROR2          jsr writestrconduc              ; output error message
                ldu curline                     ; are we in immediate mode?
                beq ERROR3                      ; brif so
                ldx #inmsg                      ; point to " in "
                jsr writestrconduc              ; output " in "
                ldd 2,u                         ; get line number
                jsr print_uint16d               ; display the line number
ERROR3          lds freetop                     ; reset the stack pointer (error routine could be called anywhere)
                clr ,-s                         ; reset the call stack
                sts cstackptr
                jmp immediate                   ; go back to immediate mode
ERRORstr        ldx #errormsg                   ; point to error messages
                incb                            ; compensate for decb below
                bra ERRORstr1                   ; go find the right string
ERRORstr0       lda ,x+                         ; end of string?
                bne ERRORstr0                   ; brif not
ERRORstr1       decb                            ; at the correct message?
                bne ERRORstr0                   ; brif not - skip a message
                rts
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; Error messages
;
; Each error begins with a deferr macro invocation which will define a symbol err_slug with the next error number
;
;               deferr slug
;
; This is then followed by the error message defined with fcn.
;
; Real error numbers start at 1; 0 is used to indicate no error.
                *pragmapush list
                *pragma nolist
__errnum        set 0
deferr          macro noexpand
err_{1}         equ __errnum
__errnum        set __errnum+1
                endm
                *pragmapop list
errormsg        deferr none
                fcn 'No error'
                deferr nf
                fcn 'NEXT without FOR'
                deferr sn
                fcn 'Syntax error'
                deferr ul
                fcn 'Undefined line number'
                deferr rg
                fcn 'RETURN without GOSUB'
                deferr ov
                fcn 'Overflow'
                deferr tm
                fcn 'Type mismatch'
                deferr div0
                fcn 'Division by zero'
                deferr om
                fcn 'Out of memory'
                *pragmapop list