From f79e7a5a48181b5d7ff3170f1617e4f7ba8d0fb8 Mon Sep 17 00:00:00 2001
From: Jez Ng <jezng@fb.com>
Date: Sun, 20 Jun 2021 19:49:13 -0400
Subject: [PATCH] [lld-macho] Have inputOrder default to less than INT_MAX

We make it less than INT_MAX in order not to conflict with the ordering
of zerofill sections, which must always be placed at the end of their
segment.

This is the more structural fix for the issue addressed in {D104596}.

Reviewed By: #lld-macho, thakis

Differential Revision: https://reviews.llvm.org/D104607
---
 lld/MachO/Driver.cpp      | 1 +
 lld/MachO/OutputSection.h | 8 +++++++-
 lld/MachO/OutputSegment.h | 2 +-
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/lld/MachO/Driver.cpp b/lld/MachO/Driver.cpp
index 074695f..a162682 100644
--- a/lld/MachO/Driver.cpp
+++ b/lld/MachO/Driver.cpp
@@ -1341,6 +1341,7 @@ bool macho::link(ArrayRef<const char *> argsArr, bool canExitEarly,
           }
         }
       }
+      assert(inputSections.size() < UnspecifiedInputOrder);
     }
 
     if (config->deadStrip)
diff --git a/lld/MachO/OutputSection.h b/lld/MachO/OutputSection.h
index 45a3b48..e3a4f20 100644
--- a/lld/MachO/OutputSection.h
+++ b/lld/MachO/OutputSection.h
@@ -20,6 +20,12 @@ namespace macho {
 class InputSection;
 class OutputSegment;
 
+// The default order value for OutputSections that are not constructed from
+// InputSections (i.e. SyntheticSections). We make it less than INT_MAX in order
+// not to conflict with the ordering of zerofill sections, which must always be
+// placed at the end of their segment.
+constexpr int UnspecifiedInputOrder = std::numeric_limits<int>::max() - 1024;
+
 // Output sections represent the finalized sections present within the final
 // linked executable. They can represent special sections (like the symbol
 // table), or represent coalesced sections from the various inputs given to the
@@ -61,7 +67,7 @@ public:
   // For output sections that don't have explicit ordering requirements, their
   // output order should be based on the order of the input sections they
   // contain.
-  int inputOrder = std::numeric_limits<int>::max();
+  int inputOrder = UnspecifiedInputOrder;
 
   uint32_t index = 0;
   uint64_t addr = 0;
diff --git a/lld/MachO/OutputSegment.h b/lld/MachO/OutputSegment.h
index 10cca2a..cd1fabb 100644
--- a/lld/MachO/OutputSegment.h
+++ b/lld/MachO/OutputSegment.h
@@ -51,7 +51,7 @@ public:
   uint64_t fileOff = 0;
   uint64_t fileSize = 0;
   uint64_t vmSize = 0;
-  int inputOrder = std::numeric_limits<int>::max();
+  int inputOrder = UnspecifiedInputOrder;
   StringRef name;
   uint32_t maxProt = 0;
   uint32_t initProt = 0;
-- 
2.7.4