From b4ead2c37bcbb1f81919c68e2a2a227aac90f07c Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Mon, 17 May 2021 13:49:17 -0400
Subject: [PATCH] [lld/mac] Correctly set nextdefsym

In LC_DYSYMTAB, private externs were still emitted as exported symbols instead
of as locals.

Fixes PR50373. See bug for details.

Differential Revision: https://reviews.llvm.org/D102662
---
 lld/MachO/SyntheticSections.cpp |  5 +-
 lld/test/MachO/symtab.s         | 82 +++++++++++++++++++++++++--------
 2 files changed, 67 insertions(+), 20 deletions(-)

diff --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp
index 38c93e1f8f96..f0070fe48e69 100644
--- a/lld/MachO/SyntheticSections.cpp
+++ b/lld/MachO/SyntheticSections.cpp
@@ -753,7 +753,10 @@ void SymtabSection::finalizeContents() {
       if (!defined->includeInSymtab)
         continue;
       assert(defined->isExternal());
-      addSymbol(externalSymbols, defined);
+      if (defined->privateExtern)
+        addSymbol(localSymbols, defined);
+      else
+        addSymbol(externalSymbols, defined);
     } else if (auto *dysym = dyn_cast<DylibSymbol>(sym)) {
       if (dysym->isReferenced())
         addSymbol(undefinedSymbols, sym);
diff --git a/lld/test/MachO/symtab.s b/lld/test/MachO/symtab.s
index 2a23b3fb77f2..a2232c93f9ff 100644
--- a/lld/test/MachO/symtab.s
+++ b/lld/test/MachO/symtab.s
@@ -1,9 +1,10 @@
 # REQUIRES: x86
 # RUN: rm -rf %t && split-file %s %t
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/test.s -o %t/test.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/test2.s -o %t/test2.o
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/libfoo.s -o %t/libfoo.o
 # RUN: %lld -dylib %t/libfoo.o -o %t/libfoo.dylib
-# RUN: %lld -lSystem %t/test.o %t/libfoo.dylib -o %t/test
+# RUN: %lld -lSystem %t/test.o %t/test2.o %t/libfoo.dylib -o %t/test
 
 # RUN: llvm-readobj --syms --macho-dysymtab %t/test | FileCheck %s
 # CHECK:      Symbols [
@@ -26,6 +27,26 @@
 # CHECK-NEXT:     Value: 0x1{{[0-9a-f]*}}
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: _private_external
+# CHECK-NEXT:     PrivateExtern
+# CHECK-NEXT:     Type: Section (0xE)
+# CHECK-NEXT:     Section: __text (0x1)
+# CHECK-NEXT:     RefType: UndefinedNonLazy (0x0)
+# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Value: 0x1{{[0-9a-f]*}}
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: _private_external_weak
+# CHECK-NEXT:     PrivateExtern
+# CHECK-NEXT:     Type: Section (0xE)
+# CHECK-NEXT:     Section: __text (0x1)
+# CHECK-NEXT:     RefType: UndefinedNonLazy (0x0)
+# CHECK-NEXT:     Flags [ (0x0)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Value: 0x1{{[0-9a-f]*}}
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: _main
 # CHECK-NEXT:     Extern
 # CHECK-NEXT:     Type: Section (0xE)
@@ -56,17 +77,17 @@
 # CHECK-NEXT:     ]
 # CHECK-NEXT:     Value: 0x1{{[0-9a-f]*}}
 # CHECK-NEXT:   }
-# CHECK-NEXT:  Symbol {
-# CHECK-NEXT:    Name: __mh_execute_header (81)
-# CHECK-NEXT:    Extern
-# CHECK-NEXT:    Type: Section (0xE)
-# CHECK-NEXT:    Section: __text (0x1)
-# CHECK-NEXT:    RefType: UndefinedNonLazy (0x0)
-# CHECK-NEXT:    Flags [ (0x10)
-# CHECK-NEXT:      ReferencedDynamically (0x10)
-# CHECK-NEXT:    ]
-# CHECK-NEXT:    Value: 0x100000000
-# CHECK-NEXT:  }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: __mh_execute_header
+# CHECK-NEXT:     Extern
+# CHECK-NEXT:     Type: Section (0xE)
+# CHECK-NEXT:     Section: __text (0x1)
+# CHECK-NEXT:     RefType: UndefinedNonLazy (0x0)
+# CHECK-NEXT:     Flags [ (0x10)
+# CHECK-NEXT:       ReferencedDynamically (0x10)
+# CHECK-NEXT:     ]
+# CHECK-NEXT:     Value: 0x100000000
+# CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: dyld_stub_binder
 # CHECK-NEXT:     Extern
@@ -92,10 +113,10 @@
 # CHECK-NEXT: ]
 # CHECK-NEXT: Dysymtab {
 # CHECK-NEXT:   ilocalsym: 0
-# CHECK-NEXT:   nlocalsym: 2
-# CHECK-NEXT:   iextdefsym: 2
+# CHECK-NEXT:   nlocalsym: 4
+# CHECK-NEXT:   iextdefsym: 4
 # CHECK-NEXT:   nextdefsym: 4
-# CHECK-NEXT:   iundefsym: 6
+# CHECK-NEXT:   iundefsym: 8
 # CHECK-NEXT:   nundefsym: 2
 
 ## Verify that the first entry in the StringTable is a space, and that
@@ -110,20 +131,43 @@
 _dynamic:
 
 #--- test.s
-.globl _main, _external, _external_weak, _unreferenced
+.globl _main, _external, _private_external, _external_weak, _private_external_weak, _unreferenced
 
 .data
 _external:
-  .space 0
+  .space 1
 _local:
-  .space 0
+  .space 1
 
 .text
 .weak_definition _external_weak
 _external_weak:
-  .space 0
+  .space 1
+
+.private_extern _private_external
+_private_external:
+  .space 1
+
+.weak_definition _private_external_weak
+.private_extern _private_external_weak
+_private_external_weak:
+  .space 1
 
 _main:
+  callq _private_external
   callq _dynamic
   mov $0, %rax
   ret
+
+#--- test2.s
+## These are both already in test.s and should make it into the symbol table
+## just once.
+.globl _external_weak, _private_external_weak
+.text
+.weak_definition _external_weak
+_external_weak:
+  .space 1
+.weak_definition _private_external_weak
+.private_extern _private_external_weak
+_private_external_weak:
+  .space 1