[lld] r260185 - We should never dead strip mach header symbols.

[Pete Cooper via llvm-commits]

Author: pete
Date: Mon Feb  8 19:34:13 2016
New Revision: 260185

URL: http://llvm.org/viewvc/llvm-project?rev=260185&view=rev
Log:
We should never dead strip mach header symbols.

This was a bug in our handling of these symbols compared to ld64.

Turns out that ld64 always marks these symbols as being not dead stripped.

Modified:
    lld/trunk/lib/ReaderWriter/MachO/ExecutableAtoms.h
    lld/trunk/test/mach-o/mh_bundle_header.yaml

Modified: lld/trunk/lib/ReaderWriter/MachO/ExecutableAtoms.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/MachO/ExecutableAtoms.h?rev=260185&r1=260184&r2=260185&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/MachO/ExecutableAtoms.h (original)
+++ lld/trunk/lib/ReaderWriter/MachO/ExecutableAtoms.h Mon Feb  8 19:34:13 2016
@@ -71,7 +71,6 @@ public:
     : SimpleFile("mach_header symbols", kindHeaderObject) {
     StringRef machHeaderSymbolName;
     DefinedAtom::Scope symbolScope = DefinedAtom::scopeLinkageUnit;
-    bool noDeadStrip = false;
     StringRef dsoHandleName;
     switch (context.outputMachOType()) {
     case llvm::MachO::MH_OBJECT:
@@ -80,7 +79,6 @@ public:
     case llvm::MachO::MH_EXECUTE:
       machHeaderSymbolName = "__mh_execute_header";
       symbolScope = DefinedAtom::scopeGlobal;
-      noDeadStrip = true;
       dsoHandleName = "___dso_handle";
       break;
     case llvm::MachO::MH_FVMLIB:
@@ -112,13 +110,15 @@ public:
     if (!machHeaderSymbolName.empty())
       _definedAtoms.push_back(new (allocator()) MachODefinedAtom(
           *this, machHeaderSymbolName, symbolScope,
-          DefinedAtom::typeMachHeader, DefinedAtom::mergeNo, false, noDeadStrip,
+          DefinedAtom::typeMachHeader, DefinedAtom::mergeNo, false,
+          true /* noDeadStrip */,
           ArrayRef<uint8_t>(), DefinedAtom::Alignment(4096)));
 
     if (!dsoHandleName.empty())
       _definedAtoms.push_back(new (allocator()) MachODefinedAtom(
           *this, dsoHandleName, DefinedAtom::scopeLinkageUnit,
-          DefinedAtom::typeDSOHandle, DefinedAtom::mergeNo, false, false,
+          DefinedAtom::typeDSOHandle, DefinedAtom::mergeNo, false,
+          true /* noDeadStrip */,
           ArrayRef<uint8_t>(), DefinedAtom::Alignment(1)));
   }
 

Modified: lld/trunk/test/mach-o/mh_bundle_header.yaml
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/mach-o/mh_bundle_header.yaml?rev=260185&r1=260184&r2=260185&view=diff
==============================================================================
--- lld/trunk/test/mach-o/mh_bundle_header.yaml (original)
+++ lld/trunk/test/mach-o/mh_bundle_header.yaml Mon Feb  8 19:34:13 2016
@@ -1,5 +1,5 @@
-# RUN: lld -flavor darwin -arch x86_64  %s -bundle -o %t %p/Inputs/libSystem.yaml
-# RUN: llvm-nm -m -n %t | FileCheck %s
+# RUN: lld -flavor darwin -arch x86_64  %s -bundle -o %t %p/Inputs/libSystem.yaml && llvm-nm -m -n %t | FileCheck %s
+# RUN: lld -flavor darwin -arch x86_64  %s -bundle -dead_strip -o %t %p/Inputs/libSystem.yaml && llvm-nm -m -n %t | FileCheck %s
 #
 # Test that __mh_bundle_header symbol is available for bundles
 #
@@ -39,6 +39,7 @@ global-symbols:
     type:            N_SECT
     scope:           [ N_EXT ]
     sect:            1
+    desc:            [ N_NO_DEAD_STRIP ]
     value:           0x0000000000000000
 undefined-symbols:
   - name:            __mh_bundle_header
@@ -49,5 +50,5 @@ undefined-symbols:
 
 ...
 
-# CHECK_NOT:	__mh_bundle_header
+# CHECK: __mh_bundle_header
 # CHECK:      _foo