From e0b1faf993bab97288540769f6f5f7955b3e0996 Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mikisabate@gmail.com>
Date: Wed, 3 Sep 2025 21:31:31 +0200
Subject: Add a check for variable names
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This check ensures that asan-friendly names actually match their
expected scope.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>
---
 lib/xixanta/src/assembler.rs      | 67 +++++++++++++++++++++++++++++++++++++++
 scripts/test-e2e.sh               |  5 +++
 tests/expected/variable_names.txt |  4 +++
 tests/variable_names.s            | 25 +++++++++++++++
 4 files changed, 101 insertions(+)
 create mode 100644 tests/expected/variable_names.txt
 create mode 100644 tests/variable_names.s

diff --git a/lib/xixanta/src/assembler.rs b/lib/xixanta/src/assembler.rs
index 09f0c9d..01a1982 100644
--- a/lib/xixanta/src/assembler.rs
+++ b/lib/xixanta/src/assembler.rs
@@ -498,6 +498,13 @@ impl<'a> Assembler<'a> {
 
                     match self.evaluate_node(node.left.as_ref().unwrap()) {
                         Ok(value) => {
+                            // Check that the given name makes sense if the
+                            // address sanitizer is enable and the assigned
+                            // value is known.
+                            if self.asan_enabled && value.resolved {
+                                self.asan_check_variable_name(node, &value);
+                            }
+
                             if let Err(err) = self.context.set_variable(
                                 &node.value,
                                 &Object {
@@ -2626,6 +2633,66 @@ impl<'a> Assembler<'a> {
         }
     }
 
+    // Check that the variable name follows the coding convention as expected
+    // from the address sanitizer.
+    fn asan_check_variable_name(&mut self, node: &PNode, bundle: &Bundle) {
+        // If this is not an asan-friendly name, skip it, as it might be a
+        // constant or something else that might be catched later.
+        if !is_asan_friendly_name(&node.value.value) {
+            return;
+        }
+
+        // Let's create this object now to makes things easier for possible
+        // error messages.
+        let actual_name = node.value.value.split("::").last().unwrap_or("");
+
+        if actual_name.starts_with("zp_") {
+            if bundle.size > 1 {
+                let value = bundle.value() as usize;
+                let range = MemoryRange {
+                    name: node.value.value.to_owned(),
+                    range: (value..(value + self.asan_next_reserve as usize)),
+                };
+                self.warnings.push(Error {
+                    line: node.value.line,
+                    message: format!("you are assigning the zero-page variable {range} to something outside of zero page"),
+                    source: self.source_for(node),
+                    global: false,
+                });
+            }
+        } else if bundle.size != 2 {
+            let value = bundle.value() as usize;
+            let range = MemoryRange {
+                name: node.value.value.to_owned(),
+                range: (value..(value + self.asan_next_reserve as usize)),
+            };
+            self.warnings.push(Error {
+                line: node.value.line,
+                message: format!(
+                    "you are assigning the variable {range} to something in zero page"
+                ),
+                source: self.source_for(node),
+                global: false,
+            });
+        } else if actual_name.starts_with("wr_") {
+            let value = bundle.value() as usize;
+            let range = MemoryRange {
+                name: node.value.value.to_owned(),
+                range: (value..(value + self.asan_next_reserve as usize)),
+            };
+            if !(0x6000..0x8000).contains(&value) {
+                self.warnings.push(Error {
+                    line: node.value.line,
+                    message: format!(
+                        "you are assigning the variable {range} to something outside of Working RAM"
+                    ),
+                    source: self.source_for(node),
+                    global: false,
+                });
+            }
+        }
+    }
+
     fn to_relative_address(&self, node: &PNode, bundle: &mut Bundle) -> Result<(), Error> {
         if !bundle.resolved {
             return Ok(());
diff --git a/scripts/test-e2e.sh b/scripts/test-e2e.sh
index ab7312b..1c94cfd 100755
--- a/scripts/test-e2e.sh
+++ b/scripts/test-e2e.sh
@@ -61,6 +61,11 @@ echo "test: custom => bare_accesses.nes"
 diff tests/out/bare_accesses.txt tests/expected/bare_accesses.txt
 exit_code=$((exit_code + $?))
 
+echo "test: custom => variable_names.nes"
+./target/debug/nasm -c empty --asan tests/variable_names.s 2>tests/out/variable_names.txt
+diff tests/out/variable_names.txt tests/expected/variable_names.txt
+exit_code=$((exit_code + $?))
+
 ##
 # code.nes
 
diff --git a/tests/expected/variable_names.txt b/tests/expected/variable_names.txt
new file mode 100644
index 0000000..416ca69
--- /dev/null
+++ b/tests/expected/variable_names.txt
@@ -0,0 +1,4 @@
+warning: you are assigning the zero-page variable 'zp_bad' ($0300) to something outside of zero page (variable_names.s: line 11)
+warning: you are assigning the variable 'm_bad' ($02) to something in zero page (variable_names.s: line 13)
+warning: you are assigning the variable 'wr_bad' ($01) to something in zero page (variable_names.s: line 14)
+warning: you are assigning the variable 'wr_out' ($0400) to something outside of Working RAM (variable_names.s: line 16)
diff --git a/tests/variable_names.s b/tests/variable_names.s
new file mode 100644
index 0000000..0859473
--- /dev/null
+++ b/tests/variable_names.s
@@ -0,0 +1,25 @@
+.segment "HEADER"
+    .byte 'N', 'E', 'S', $1A
+    .byte $02
+    .byte $01
+    .byte $12                   ; let's fake working RAM
+    .byte $00
+
+.segment "CODE"
+
+zp_good  = $00
+zp_bad   = $0300
+m_good   = $0200
+m_bad    = $02
+wr_bad   = $01
+wr_good  = $6001
+wr_out   = $0400
+
+;; Just so we don't get "unused" warnings
+lda zp_bad
+lda zp_good
+lda m_bad
+lda m_good
+lda wr_bad
+lda wr_good
+lda wr_out
-- 
cgit v1.2.3