Add overflow_error

src/basic/,basic_aliases.s

@@ -8,7 +8,11 @@
 !addr memmove__size   = RESHO+2
 !addr memmove__tmp    = RESHO+4
 
+;
+; Error codes
+;
 
+err_overflow = $0F
 
 ;
 ; Helper aliases to make the code more readable

src/basic/,stubs/a437.error.s

@@ -0,0 +1,12 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+
+
+; XXX provide documentation and implementation
+
+error:
+
+    +STUB_IMPLEMENTATION

src/basic/math/b97e.overflow_error.s

@@ -0,0 +1,17 @@
+;; #LAYOUT# STD *       #TAKE
+;; #LAYOUT# X16 BASIC_0 #TAKE-OFFSET 2000
+;; #LAYOUT# *   BASIC_0 #TAKE
+;; #LAYOUT# *   *       #IGNORE
+
+; This file is under the MIT license, it contains code released by Microsoft Corporation.
+; See LICENSE for more information.
+
+; Math package - overflow error
+;
+; This is verified to be identical to the original Microsoft implementation where it was named OVERR.
+;
+
+overflow_error:
+
+    ldx #err_overflow
+    jmp error

src/basic/math/mul10_FAC1_mul2.s

@@ -11,6 +11,6 @@ mul10_FAC1_mul2:
 	; Increment the exponent
 
 	inc FAC1_exponent
-	+beq set_FAC1_max
+	+beq overflow_error
 
 	rts

src/basic/math/mul_FAC2_FAC1.s

@@ -64,7 +64,7 @@ mul_FAC2_FAC1:
 	sta RESHO+1
 @2:
 	lda RESHO+1
-	+bne set_FAC1_max                ; overflow
+	+bne overflow_error               ; overflow
 
 	lda RESHO+0
 	sta FAC1_exponent
@@ -124,7 +124,7 @@ mul_FAC2_FAC1:
 	lda FAC1_exponent
 	clc
 	adc #$08
-	+bcs set_FAC1_max                ; branch if overflow
+	+bcs overflow_error                ; branch if overflow
 	sta FAC1_exponent
 	jmp normal_FAC1