From 0a7e56f74c2adde9a4bc2c1163e7ed3aff984584 Mon Sep 17 00:00:00 2001
From: Jez Ng <jezng@fb.com>
Date: Mon, 31 Aug 2020 20:32:39 -0700
Subject: [PATCH] [lld-macho] Mark weak symbols in symbol table

Reviewed By: #lld-macho, smeenai

Differential Revision: https://reviews.llvm.org/D86908
---
 lld/MachO/SyntheticSections.cpp | 3 ++-
 lld/test/MachO/symtab.s         | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp
index 66dcbde..0106426 100644
--- a/lld/MachO/SyntheticSections.cpp
+++ b/lld/MachO/SyntheticSections.cpp
@@ -473,10 +473,11 @@ void SymtabSection::writeTo(uint8_t *buf) const {
   for (const SymtabEntry &entry : symbols) {
     nList->n_strx = entry.strx;
     // TODO support other symbol types
-    // TODO populate n_desc
+    // TODO populate n_desc with more flags
     if (auto *defined = dyn_cast<Defined>(entry.sym)) {
       nList->n_type = MachO::N_EXT | MachO::N_SECT;
       nList->n_sect = defined->isec->parent->index;
+      nList->n_desc |= defined->isWeakDef() ? MachO::N_WEAK_DEF : 0;
       // For the N_SECT symbol type, n_value is the address of the symbol
       nList->n_value = defined->value + defined->isec->getVA();
     }
diff --git a/lld/test/MachO/symtab.s b/lld/test/MachO/symtab.s
index 44a0169..1efa7a2 100644
--- a/lld/test/MachO/symtab.s
+++ b/lld/test/MachO/symtab.s
@@ -20,7 +20,8 @@
 # CHECK-NEXT:     Type: Section (0xE)
 # CHECK-NEXT:     Section: __text (0x1)
 # CHECK-NEXT:     RefType:
-# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     Flags [ (0x80)
+# CHECK-NEXT:       WeakDef (0x80)
 # CHECK-NEXT:     ]
 # CHECK-NEXT:     Value:
 # CHECK-NEXT:   }
@@ -42,6 +43,7 @@ foo:
   .asciz "Hello world!\n"
 
 .text
+.weak_definition bar
 .global bar
 .global _main
 
-- 
2.7.4