Ignore extern symbols with symbol name lookups

When searching for a symbol by name, only look at
symbols that are defined within the object,
ignoring extern symbols (symbols without section).

Fixes #180
Fixes #181

objdiff-cli/src/views/function_diff.rs

@@ -450,11 +450,11 @@ impl UiView for FunctionDiffUi {
 
     fn reload(&mut self, state: &AppState) -> Result<()> {
         let left_sym =
-            state.left_obj.as_ref().and_then(|(o, _)| find_function(o, &self.symbol_name));
+            state.left_obj.as_ref().and_then(|(o, _)| o.symbol_by_name(&self.symbol_name));
         let right_sym =
-            state.right_obj.as_ref().and_then(|(o, _)| find_function(o, &self.symbol_name));
+            state.right_obj.as_ref().and_then(|(o, _)| o.symbol_by_name(&self.symbol_name));
         let prev_sym =
-            state.prev_obj.as_ref().and_then(|(o, _)| find_function(o, &self.symbol_name));
+            state.prev_obj.as_ref().and_then(|(o, _)| o.symbol_by_name(&self.symbol_name));
         self.num_rows = match (
             get_symbol(state.left_obj.as_ref(), left_sym),
             get_symbol(state.right_obj.as_ref(), right_sym),
@@ -650,12 +650,3 @@ fn get_symbol(
     let sym = sym?;
     Some((obj, sym, &diff.symbols[sym]))
 }
-
-fn find_function(obj: &Object, name: &str) -> Option<usize> {
-    for (symbol_idx, symbol) in obj.symbols.iter().enumerate() {
-        if symbol.name == name {
-            return Some(symbol_idx);
-        }
-    }
-    None
-}

objdiff-core/src/diff/mod.rs

@@ -391,7 +391,7 @@ fn generate_mapping_symbols(
         MappingSymbol::Left(name) => (left_obj, name, right_obj),
         MappingSymbol::Right(name) => (right_obj, name, left_obj),
     };
-    let Some(base_symbol_ref) = symbol_ref_by_name(base_obj, base_name) else {
+    let Some(base_symbol_ref) = base_obj.symbol_by_name(base_name) else {
         return Ok(());
     };
     let base_section_kind = symbol_section_kind(base_obj, &base_obj.symbols[base_symbol_ref]);
@@ -457,10 +457,6 @@ pub struct MappingConfig {
     pub selecting_right: Option<String>,
 }
 
-fn symbol_ref_by_name(obj: &Object, name: &str) -> Option<usize> {
-    obj.symbols.iter().position(|s| s.name == name)
-}
-
 fn apply_symbol_mappings(
     left: &Object,
     right: &Object,
@@ -472,25 +468,25 @@ fn apply_symbol_mappings(
     // If we're selecting a symbol to use as a comparison, mark it as used
     // This ensures that we don't match it to another symbol at any point
     if let Some(left_name) = &mapping_config.selecting_left {
-        if let Some(left_symbol) = symbol_ref_by_name(left, left_name) {
+        if let Some(left_symbol) = left.symbol_by_name(left_name) {
             left_used.insert(left_symbol);
         }
     }
     if let Some(right_name) = &mapping_config.selecting_right {
-        if let Some(right_symbol) = symbol_ref_by_name(right, right_name) {
+        if let Some(right_symbol) = right.symbol_by_name(right_name) {
             right_used.insert(right_symbol);
         }
     }
 
     // Apply manual symbol mappings
     for (left_name, right_name) in &mapping_config.mappings {
-        let Some(left_symbol_index) = symbol_ref_by_name(left, left_name) else {
+        let Some(left_symbol_index) = left.symbol_by_name(left_name) else {
             continue;
         };
         if left_used.contains(&left_symbol_index) {
             continue;
         }
-        let Some(right_symbol_index) = symbol_ref_by_name(right, right_name) else {
+        let Some(right_symbol_index) = right.symbol_by_name(right_name) else {
             continue;
         };
         if right_used.contains(&right_symbol_index) {

objdiff-core/src/obj/mod.rs

@@ -308,6 +308,10 @@ impl Object {
         let offset = symbol.address.checked_sub(section.address)?;
         section.data.get(offset as usize..offset as usize + symbol.size as usize)
     }
+
+    pub fn symbol_by_name(&self, name: &str) -> Option<usize> {
+        self.symbols.iter().position(|symbol| symbol.section.is_some() && symbol.name == name)
+    }
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]

objdiff-gui/src/views/diff.rs

@@ -49,7 +49,9 @@ impl<'a> DiffColumnContext<'a> {
         let selected_symbol = match view {
             View::SymbolDiff => None,
             View::FunctionDiff | View::ExtabDiff => match (obj, selected_symbol) {
-                (Some(obj), Some(s)) => find_symbol(&obj.0, s).map(SelectedSymbol::Symbol),
+                (Some(obj), Some(s)) => {
+                    obj.0.symbol_by_name(&s.symbol_name).map(SelectedSymbol::Symbol)
+                }
                 _ => None,
             },
             View::DataDiff => match (obj, selected_symbol) {
@@ -779,10 +781,6 @@ fn missing_obj_ui(ui: &mut Ui, appearance: &Appearance) {
     });
 }
 
-fn find_symbol(obj: &Object, selected_symbol: &SymbolRefByName) -> Option<usize> {
-    obj.symbols.iter().position(|symbol| symbol.name == selected_symbol.symbol_name)
-}
-
 fn find_section(obj: &Object, section_name: &str) -> Option<usize> {
     obj.sections.iter().position(|section| section.name == section_name)
 }