range check char length

twasm/asm/main.asm

@@ -866,7 +866,8 @@ evaluate_constant:
     jmp .bin_loop
 
   .chr:
-    ; TODO range check rcx
+    cmp rcx, 4       ; ensure char is only 4 bytes long
+    jg .unrecognised
     cmp rsi, 1 ; range check
     je .chr_break
 
@@ -896,7 +897,7 @@ evaluate_constant:
     jmp .chr_break
 
   .chr_break_for_good:
-    mov dl, [rdi]
+    mov dl, [rdi] ; make sure the chr is closed
     cmp dl, '"'
     jne .unrecognised
 

twasm/asm/tests.asm

@@ -377,6 +377,13 @@ test_evaluate_constant:
   cmp rdx, 0x03
   jne .fail
 
+  ; oversized char
+  mov rdi, .case1c
+  mov rsi, 7
+  call evaluate_constant
+  cmp rdx, 0xFF
+  jne .fail
+
   .pass:
     mov rsi, msg_pass
     call print
@@ -396,6 +403,8 @@ test_evaluate_constant:
   .case3h_solution dq 0x243F6A8885A308D3
   .case0c db '"char"'
   .case0c_solution dq "char"
+  .case1c db '"chars"'
+  .case1c_solution dq "chars"
 
   .case0q db "0q31103755242102"
   .case0q_solution dq 0q31103755242102