From d88fab8c004b3f2556714725bc1e9d48ec6c619f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miquel=20Sabat=C3=A9=20Sol=C3=A0?= <mikisabate@gmail.com>
Date: Fri, 20 Dec 2024 16:20:12 +0100
Subject: [PATCH] Prevent a division by zero
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Fixes: 8b5feeed96b3 ("assembler: Implement and add tests for operators")

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
---
 lib/xixanta/src/assembler.rs | 51 ++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/lib/xixanta/src/assembler.rs b/lib/xixanta/src/assembler.rs
index 4fd8d92..e6f3396 100644
--- a/lib/xixanta/src/assembler.rs
+++ b/lib/xixanta/src/assembler.rs
@@ -641,6 +641,13 @@ impl Assembler {
                 lval * rval
             }
             OperationType::Div => {
+                if rval == 0 {
+                    return Err(EvalError {
+                        line: node.value.line,
+                        global: false,
+                        message: "attempting to divide by zero".to_string(),
+                    });
+                }
                 let lval = self.evaluate_node(node.left.as_ref().unwrap())?.value();
                 lval / rval
             }
@@ -1994,6 +2001,50 @@ ldx #+Value
         assert_eq!(pos.bytes[2], 0x00);
     }
 
+    #[test]
+    fn divide_by_zero() {
+        let mut asm = Assembler::new(EMPTY.to_vec());
+        asm.mappings[0].segments[0].bundles = minimal_header();
+        asm.mappings[0].offset = 6;
+        asm.current_mapping = 1;
+        let res = &asm
+            .assemble(
+                std::env::current_dir().unwrap().to_path_buf(),
+                r#"Value = 0
+ldx #(2 / Value)
+"#
+                .as_bytes(),
+            )
+            .unwrap_err();
+
+        assert_eq!(
+            res.first().unwrap().to_string(),
+            "attempting to divide by zero (line 2)"
+        );
+    }
+
+    #[test]
+    fn bad_shift() {
+        let mut asm = Assembler::new(EMPTY.to_vec());
+        asm.mappings[0].segments[0].bundles = minimal_header();
+        asm.mappings[0].offset = 6;
+        asm.current_mapping = 1;
+        let res = &asm
+            .assemble(
+                std::env::current_dir().unwrap().to_path_buf(),
+                r#"Value = #$11
+ldx #(2 << Value)
+"#
+                .as_bytes(),
+            )
+            .unwrap_err();
+
+        assert_eq!(
+            res.first().unwrap().to_string(),
+            "shift operator too big (line 2)"
+        );
+    }
+
     // Regular instructions
 
     #[test]