From 3e2a34116833ec0a01cc2c3d4353834aef7a693a Mon Sep 17 00:00:00 2001
From: Konstantin Mandrika <kmandrika@google.com>
Date: Thu, 30 Jun 2022 14:29:08 -0400
Subject: [PATCH] Handle abbrev entities being out of order.

There are cases where the debug_abbrev entities are not sequential,
for example, in Xamarin system dlls. This change gracefully handles
such a case.

Change-Id: Ib270393d3cf9fd18efd99d15d0fba4f96748188a
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/3738879
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
---
 src/common/dwarf/dwarf2reader.cc | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/common/dwarf/dwarf2reader.cc b/src/common/dwarf/dwarf2reader.cc
index bf6758d8..11854b4b 100644
--- a/src/common/dwarf/dwarf2reader.cc
+++ b/src/common/dwarf/dwarf2reader.cc
@@ -129,10 +129,13 @@ void CompilationUnit::ReadAbbrevs() {
   const uint64_t abbrev_length = iter->second.second - header_.abbrev_offset;
 #endif
 
+  uint64_t highest_number = 0;
+
   while (1) {
     CompilationUnit::Abbrev abbrev;
     size_t len;
     const uint64_t number = reader_->ReadUnsignedLEB128(abbrevptr, &len);
+    highest_number = std::max(highest_number, number);
 
     if (number == 0)
       break;
@@ -170,9 +173,17 @@ void CompilationUnit::ReadAbbrevs() {
                            value);
       abbrev.attributes.push_back(abbrev_attr);
     }
-    assert(abbrev.number == abbrevs_->size());
     abbrevs_->push_back(abbrev);
   }
+
+  // Account of cases where entries are out of order.
+  std::sort(abbrevs_->begin(), abbrevs_->end(),
+    [](const CompilationUnit::Abbrev& lhs, const CompilationUnit::Abbrev& rhs) {
+      return lhs.number < rhs.number;
+  });
+
+  // Ensure that there are no missing sections.
+  assert(abbrevs_->size() == highest_number + 1);
 }
 
 // Skips a single DIE's attributes.