fix datasize() on last label of struct

Author: trillllian

src/asar/assembleblock.cpp

@@ -1320,6 +1320,14 @@ void cmd_endstruct(char** words, int numwords) {
 		structs.create(struct_parent) = parent;
 	}
 
+	// create a fake label for the end, so that datasize() acts nicer on the last label in the struct
+	string endname = STR ":endstruct_";
+	if(in_sub_struct) {
+		endname += struct_parent + ".";
+	}
+	endname += struct_name;
+	setlabel(endname, snespos, static_struct);
+
 	pop_pc();
 	in_struct = false;
 	in_sub_struct = false;

tests/datasize.asm

@@ -1,14 +1,26 @@
-;`A9 03 00 A9 F3 7F A9 09 00 00 00 02
-;`warnWdatasize_last_label
-;`warnWdatasize_exceeds_size
+struct wat $0000
+	.first: skip 5
+	.last: skip 2
+endstruct
+
 org $008000
 main:
 
-lda #datasize(my_table)		;3
-lda #datasize(other_label)	;0xFFFFFF
-lda #datasize(main)		;9
-
+;`A9 03 00
+lda #datasize(my_table)
+;`A9 F3 7F
+;`warnWdatasize_last_label
+;`warnWdatasize_exceeds_size
+lda #datasize(other_label)
+;`A9 09 00
+lda #datasize(main)
 
 my_table:
+;`00 00 02
 	db $00, $00, $02
 other_label:
+
+;`a9 05
+lda #datasize(wat.first)
+;`a9 02
+lda #datasize(wat.last)