Sort all symbols by address when reading the object

This fixes an underreport bug in diff_bss_section.

Author: LagoLunatic

objdiff-core/src/diff/mod.rs

@@ -748,14 +748,11 @@ fn find_symbol(
     }
 
     // Try to find a symbol with a matching name
-    if let Some((symbol_idx, _)) = unmatched_symbols(obj, used)
-        .filter(|&(_, symbol)| {
-            symbol_name_matches(in_symbol, symbol)
-                && symbol_section_kind(obj, symbol) == section_kind
-                && symbol_section(obj, symbol).is_some_and(|(name, _)| name == section_name)
-        })
-        .min_by_key(|&(_, symbol)| (symbol.section, symbol.address))
-    {
+    if let Some((symbol_idx, _)) = unmatched_symbols(obj, used).find(|&(_, symbol)| {
+        symbol_name_matches(in_symbol, symbol)
+            && symbol_section_kind(obj, symbol) == section_kind
+            && symbol_section(obj, symbol).is_some_and(|(name, _)| name == section_name)
+    }) {
         return Some(symbol_idx);
     }
 

objdiff-core/src/obj/read.rs

@@ -8,6 +8,7 @@ use alloc::{
 use core::{cmp::Ordering, num::NonZeroU64};
 
 use anyhow::{Context, Result, anyhow, bail, ensure};
+use itertools::Itertools;
 use object::{Object as _, ObjectSection as _, ObjectSymbol as _};
 
 use crate::{
@@ -166,7 +167,13 @@ fn map_symbols(
     let symbol_count = obj_file.symbols().count();
     let mut symbols = Vec::<Symbol>::with_capacity(symbol_count + obj_file.sections().count());
     let mut symbol_indices = Vec::<usize>::with_capacity(symbol_count + 1);
-    for obj_symbol in obj_file.symbols() {
+    let obj_symbols = obj_file.symbols();
+    // symbols() is not guaranteed to be sorted by address.
+    // We sort it here to fix pairing bugs with diff algorithms that assume the symbols are ordered.
+    // Sorting everything here once is less expensive than sorting subsets later in expensive loops.
+    let obj_symbols =
+        obj_symbols.sorted_by_key(|symbol| (symbol.section_index().map(|i| i.0), symbol.address()));
+    for obj_symbol in obj_symbols {
         if symbol_indices.len() <= obj_symbol.index().0 {
             symbol_indices.resize(obj_symbol.index().0 + 1, usize::MAX);
         }