From d869a040ee8812595939c2d7cd258f01dcf18a7c Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Sun, 24 Apr 2016 02:31:02 +0000
Subject: [PATCH] ELF: Always include undefined DSO symbols in the symbol
 table.

Fixes check-llvm when bootstrapping.

Also remove mostly dead and most likely incorrect logic regarding preemption
of weak undefined symbols.

llvm-svn: 267314
---
 lld/ELF/Symbols.cpp                 | 11 ++++-----
 lld/test/ELF/undef-version-script.s | 37 +++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 7 deletions(-)
 create mode 100644 lld/test/ELF/undef-version-script.s

diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index 1b8234871b54..5bb6a7033839 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -123,13 +123,9 @@ bool SymbolBody::isPreemptible() const {
   if (!Config->Shared)
     return false;
 
-  // Undefined symbols in DSOs can only be preempted if they are strong.
-  // Weak symbols just resolve to zero.
-  if (isUndefined())
-    return !isWeak();
-
   // -Bsymbolic means that not even default visibility symbols can be preempted.
-  if (Config->Bsymbolic || (Config->BsymbolicFunctions && isFunc()))
+  if ((Config->Bsymbolic || (Config->BsymbolicFunctions && isFunc())) &&
+      isDefined())
     return false;
 
   // Only default visibility symbols that appear in the dynamic symbol table can
@@ -323,7 +319,8 @@ std::string elf::demangle(StringRef Name) {
 bool Symbol::includeInDynsym() const {
   if (Visibility != STV_DEFAULT && Visibility != STV_PROTECTED)
     return false;
-  return (ExportDynamic && VersionScriptGlobal) || Body->isShared();
+  return (ExportDynamic && VersionScriptGlobal) || Body->isShared() ||
+         Body->isUndefined();
 }
 
 template uint32_t SymbolBody::template getVA<ELF32LE>(uint32_t) const;
diff --git a/lld/test/ELF/undef-version-script.s b/lld/test/ELF/undef-version-script.s
new file mode 100644
index 000000000000..a942d19b2e8f
--- /dev/null
+++ b/lld/test/ELF/undef-version-script.s
@@ -0,0 +1,37 @@
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "{ local: *; };" > %t.script
+# RUN: ld.lld --version-script %t.script -shared %t.o -o %t.so
+# RUN: llvm-readobj -dyn-symbols %t.so | FileCheck %s
+
+# CHECK:      DynamicSymbols [
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: @ (0)
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Local (0x0)
+# CHECK-NEXT:     Type: None (0x0)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: bar@ (1)
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Weak (0x2)
+# CHECK-NEXT:     Type: None (0x0)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: foo@ (5)
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Global (0x1)
+# CHECK-NEXT:     Type: None (0x0)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+.global foo
+.weak bar