Check overflow errors in the parsing bytecode buffer.

Don't simply emit bad code on lines with too long bytecode.

Author: dmsc

src/actions.asm

@@ -41,7 +41,7 @@
         .import         alloc_laddr
         .importzp       prog_ptr, laddr_ptr, laddr_buf, var_ptr, label_ptr
         ; From parser.asm
-        .import         parser_error, parser_skipws
+        .import         parser_error, parser_skipws, parser_emit_byte
         .importzp       TOK_CSTRING
         ; From error.asm
         .importzp       ERR_LOOP
@@ -141,15 +141,10 @@ ok:     rts
 ;
 ; Emits 16bit AX into codep
 .proc   emit_AX
-        ldy     opos
-new_y:  sta     (prog_ptr),y
-        txa
-        iny
-        sta     (prog_ptr),y
-        iny
-        sty     opos
         clc
-        rts
+        jsr     parser_emit_byte
+        txa
+        jmp     parser_emit_byte
 .endproc
 
 ; Parser external subs
@@ -286,9 +281,7 @@ nloop:
         ; Store
 store:  inx
         inc     bpos
-        ldy     opos
-        sta     (prog_ptr),y
-        inc     opos
+        jsr     parser_emit_byte
         bne     nloop
 err:    ; Restore opos and exit
         lda     tmp1
@@ -379,9 +372,7 @@ exit:
 .proc   emit_varn
         ; Store VARN
         txa
-        ldy     opos
-        sta     (prog_ptr),y
-        inc     opos
+        jsr     parser_emit_byte
         ; Fall through
 .endproc
         ; Advances variable name in source pointer

src/errors.asm

@@ -34,7 +34,8 @@ error_msg_list:
         .endrepeat
         .byte   .strat(msg, .strlen(msg)-1) ^ $80
 .endmacro
-        def_error ERR_LOOP,     "bad loop error"
+        def_error ERR_TOO_LONG, "too long"
+        def_error ERR_LOOP,     "bad loop"
         def_error ERR_PARSE,    "parse error"
         def_error ERR_NO_ELOOP, "no end loop/proc/if"
         def_error ERR_LABEL,    "undef label"

src/parse.asm

@@ -19,7 +19,7 @@
 ; Parser state machine interpreter
 ; --------------------------------
 
-        .export         parser_start, parser_error, parser_skipws
+        .export         parser_start, parser_error, parser_skipws, parser_emit_byte
         ; Parser state
         .exportzp       bptr, bpos, bmax, linenum, buf_ptr, end_ptr
         .exportzp       loop_sp
@@ -42,7 +42,7 @@
         .importzp       DEGFLAG, DEGFLAG_DEG, DEGFLAG_RAD
         ; From errors.asm
         .import         error_msg_list
-        .importzp       ERR_PARSE, ERR_NO_ELOOP, ERR_LABEL
+        .importzp       ERR_PARSE, ERR_NO_ELOOP, ERR_LABEL, ERR_TOO_LONG
 
         .zeropage
 buf_ptr:.res 2
@@ -96,6 +96,17 @@ SM_EMIT=        SM_EMIT_1
 ; Now, the rest of the code
         .code
 
+emit_sub:
+        jsr     parser_fetch
+emit_const:
+parser_emit_byte:
+        ldy     opos
+        sta     (prog_ptr),y
+        inc     opos
+        bne     rts1
+        lda     #ERR_TOO_LONG
+        ; Fall through
+
 .proc parser_error
         ; Prints error message
         tax
@@ -116,7 +127,7 @@ skip:   bpl     ploop
 ::restore_stack:
         ldx     #$ff
         txs
-        rts
+::rts1: rts
 .endproc
 saved_stack = restore_stack + 1
 
@@ -393,12 +404,4 @@ set_parse_error:
         lda     #ERR_PARSE
         jmp     parser_error
 
-emit_sub:
-        jsr     parser_fetch
-emit_const:
-        ldy     opos
-        sta     (prog_ptr),y
-        inc     opos
-        rts
-
 ; vi:syntax=asm_ca65