improved error handling in BASIC

src/basic/basic_commands/cmd_run_goto.s

@@ -24,6 +24,7 @@ cmd_goto:
 	bcs !+
 
 	jsr fetch_line_number
+	bcs_16 do_SYNTAX_error
 	jsr find_line
 	bcc !+
 	// Line does not exist, so report error

src/basic/basic_commands/cmd_sys.s

@@ -41,7 +41,9 @@ cmd_sys_hack_not_needed:
 	// XXX End of hack
 	//
 
-	jsr fetch_line_number
+	lda #IDX__EV2_0B // 'SYNTAX ERROR'
+	jsr fetch_uint16
+	bcs_16 do_SYNTAX_error
 
 cmd_sys_setup_call:
 	lda #$4C // JMP opcode

src/basic/basic_commands_CC/helper_bload_fetch_address.s

@@ -12,7 +12,9 @@ helper_bload_fetch_address:
 	jsr injest_comma
 	bcs_16 do_SYNTAX_error
 
-	jsr fetch_line_number                        // XXX detect errors here
+	lda #IDX__EV2_0B // 'SYNTAX ERROR'
+	jsr fetch_uint16
+	bcs_16 do_SYNTAX_error
 
 	ldx LINNUM+0
 	ldy LINNUM+1

src/basic/engine/fetch_line_number.s

@@ -3,97 +3,19 @@
 // #LAYOUT# *   *       #IGNORE
 
 //
-// Fetches line number, stores it in LINNUM, sets Carry to indicate failure (not a number), prints SYNTAX ERROR if above 65535
+// Fetches line number, stores it in LINNUM, sets Carry to indicate failure (not a number)
 //
 // Preserves both .X and .Y
 //
 
 fetch_line_number:
 
-	// Fetch the first character (skip spaces), check if 0-9
-
-	jsr fetch_character
-	cmp #$20
-	beq fetch_line_number
-
-	jsr convert_PETSCII_to_digit
-	bcs fetch_line_number_rts
-
-	// First character seems to be correct - store it
-
-	sta LINNUM+0
-	lda #$00
-	sta LINNUM+1
-
-	// FALLTROUGH
-
-fetch_line_number_loop:
-
-	// Try to fetch another digit
-
-	jsr fetch_character
-	jsr convert_PETSCII_to_digit
-	bcs fetch_line_number_end
-
-	// We got another digit - store it
-
-	pha
-
-	// Multiply current LINNUM by 10 (x * 10 = (x * 2) + (x * 2) * 4)
-
-	jsr fetch_line_number_mul_LINNUM_2
+	lda #IDX__EV7_26 // 'LINE NUMBER TOO LARGE'
+	jsr fetch_uint16
+	bcs_16 do_SYNTAX_error
 
 	lda LINNUM+1
-	pha
-	lda LINNUM+0
-	pha
-
-	jsr fetch_line_number_mul_LINNUM_2
-	jsr fetch_line_number_mul_LINNUM_2
-
-	clc
-	pla
-	adc LINNUM+0
-	sta LINNUM+0
-	pla
-	adc LINNUM+1
-	sta LINNUM+1
-	bcs_16 do_SYNTAX_error
-
-	// Add the new digit to LINNUM
-
-	pla
-	clc
-	adc LINNUM+0
-	sta LINNUM+0
-	lda LINNUM+1
-	adc #$00
-	sta LINNUM+1
-	bcs_16 do_SYNTAX_error
-
-	// Next iteration
-
-#if HAS_OPCODES_65C02
-	bra fetch_line_number_loop
-#else
-	jmp fetch_line_number_loop
-#endif
-
-fetch_line_number_end:
-
-	jsr unconsume_character
-	clc
-
-	// FALLTROUGH
-
-fetch_line_number_rts:
-
-	rts
-
-fetch_line_number_mul_LINNUM_2:
-
-	asl LINNUM+0
-	rol LINNUM+1
-	bcs_16 do_SYNTAX_error
+	cmp #$FF
+	beq_16 do_LINE_NUMBER_TOO_LARGE_error
 
 	rts

src/basic/engine/fetch_uint16.s

@@ -0,0 +1,126 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Fetches unsigned 16-bit integer, stores it in LINNUM, sets Carry to indicate failure (not a number)
+//
+// If value above 65535, error depends on .A opn entry
+//
+// Preserves both .X and .Y
+//
+
+fetch_uint16:
+
+	// Push the error code to stack
+
+	pha
+
+	// Fetch the first character (skip spaces), check if 0-9
+
+	jsr fetch_character
+	cmp #$20
+	beq fetch_uint16
+
+	jsr convert_PETSCII_to_digit
+	bcs fetch_uint16_rts
+
+	// First character seems to be correct - store it
+
+	sta LINNUM+0
+	lda #$00
+	sta LINNUM+1
+
+	// FALLTROUGH
+
+fetch_uint16_loop:
+
+	// Try to fetch another digit
+
+	jsr fetch_character
+	jsr convert_PETSCII_to_digit
+	bcs fetch_uint16_end
+
+	// We got another digit - store it
+
+	pha
+
+	// Multiply current LINNUM by 10 (x * 10 = (x * 2) + (x * 2) * 4)
+
+	jsr fetch_uint16_mul_LINNUM_2
+	bcs fetch_uint16_1PLA_error
+
+	lda LINNUM+1
+	pha
+	lda LINNUM+0
+	pha
+
+	jsr fetch_uint16_mul_LINNUM_2
+	bcs fetch_uint16_3PLA_error
+	jsr fetch_uint16_mul_LINNUM_2
+	bcs fetch_uint16_3PLA_error
+
+	clc
+	pla
+	adc LINNUM+0
+	sta LINNUM+0
+	pla
+	adc LINNUM+1
+	sta LINNUM+1
+	bcs fetch_uint16_1PLA_error
+
+	// Add the new digit to LINNUM
+
+	pla
+	clc
+	adc LINNUM+0
+	sta LINNUM+0
+	lda LINNUM+1
+	adc #$00
+	sta LINNUM+1
+	bcs fetch_uint16_error
+
+	// Next iteration
+
+#if HAS_OPCODES_65C02
+	bra fetch_uint16_loop
+#else
+	jmp fetch_uint16_loop
+#endif
+
+fetch_uint16_end:
+
+	jsr unconsume_character
+	clc
+
+	// FALLTROUGH
+
+fetch_uint16_rts:
+
+	pla
+	rts
+
+fetch_uint16_mul_LINNUM_2:
+
+	asl LINNUM+0
+	rol LINNUM+1
+
+	rts
+
+fetch_uint16_3PLA_error:
+
+	pla
+	pla
+
+	// FALLTROUGH
+
+fetch_uint16_1PLA_error:
+
+	pla
+
+	// FALLTROUGH
+
+fetch_uint16_error:
+
+	plx_trash_a
+	jmp do_basic_error

src/basic/engine/fetch_uint8.s

@@ -17,7 +17,9 @@ fetch_coma_uint8:
 fetch_uint8:
 
 	jsr injest_spaces
-	jsr fetch_line_number                        // XXX detect errors here
+	lda #IDX__EV2_0E                             // 'ILLEGAL QUANTITY ERROR'
+	jsr fetch_uint16
+	bcs !+
 	lda LINNUM+1
 	bne_16 do_ILLEGAL_QUANTITY_error
 	lda LINNUM+0

src/basic/wedge/wedge_dos.s

@@ -83,13 +83,7 @@ wedge_dos_command:
 
 wedge_dos_change_drive:
 
-	// Reuse the line number parser for device number retrieval
-	jsr fetch_line_number
-	lda LINNUM+1
-	beq !+
-	jmp do_ILLEGAL_QUANTITY_error
-!:
-	lda LINNUM+0
+	jsr fetch_uint8
 	cmp #$08
 	bpl !+
 	bcs !+