[lld:MachO] Allow independent override of weak symbols aliased via .set

lld/MachO/SymbolTable.cpp

@@ -78,22 +78,23 @@ static void transplantSymbolsAtOffset(InputSection *fromIsec,
   auto insertIt = llvm::upper_bound(toIsec->symbols, toOff, symSucceedsOff);
   llvm::erase_if(fromIsec->symbols, [&](Symbol *s) {
     auto *d = cast<Defined>(s);
-    if (d->value != fromOff)
+    if (d == skip)
+      return true;
+    if (d->value != fromOff || d->isExternal())
       return false;
-    if (d != skip) {
-      // This repeated insertion will be quadratic unless insertIt is the end
-      // iterator. However, that is typically the case for files that have
-      // .subsections_via_symbols set.
-      insertIt = toIsec->symbols.insert(insertIt, d);
-      d->originalIsec = toIsec;
-      d->value = toOff;
-      // We don't want to have more than one unwindEntry at a given address, so
-      // drop the redundant ones. We We can safely drop the unwindEntries of
-      // the symbols in fromIsec since we will be adding another unwindEntry as
-      // we finish parsing toIsec's file. (We can assume that toIsec has its
-      // own unwindEntry because of the ODR.)
-      d->originalUnwindEntry = nullptr;
-    }
+
+    // This repeated insertion will be quadratic unless insertIt is the end
+    // iterator. However, that is typically the case for files that have
+    // .subsections_via_symbols set.
+    insertIt = toIsec->symbols.insert(insertIt, d);
+    d->originalIsec = toIsec;
+    d->value = toOff;
+    // We don't want to have more than one unwindEntry at a given address, so
+    // drop the redundant ones. We We can safely drop the unwindEntries of
+    // the symbols in fromIsec since we will be adding another unwindEntry as
+    // we finish parsing toIsec's file. (We can assume that toIsec has its
+    // own unwindEntry because of the ODR.)
+    d->originalUnwindEntry = nullptr;
     return true;
   });
 }

lld/test/MachO/weak-alias-override.s

@@ -0,0 +1,97 @@
+# REQUIRES: x86
+# RUN: rm -rf %t; split-file %s %t
+# RUN: mkdir -p %t/bin
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/weak.o %t/weak.s
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/strong_a.o %t/strong_a.s
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/strong_b.o %t/strong_b.s
+
+# --- Test Case 1: No overrides
+# RUN: %lld %t/weak.o -o %t/bin/alone -e _s
+# RUN: llvm-nm -am %t/bin/alone | FileCheck --check-prefix=NM_ALONE %s
+
+# NM_ALONE:            [[P_ADDR:[0-9a-f]+]] (__TEXT,__const) weak external _placeholder_int
+# NM_ALONE:            [[P_ADDR]] (__TEXT,__const) weak external _weak_a
+# NM_ALONE:            [[P_ADDR]] (__TEXT,__const) weak external _weak_b
+
+# --- Test Case 2: Override weak_a
+# RUN: %lld %t/weak.o %t/strong_a.o -o %t/bin/with_a -e _s
+# RUN: llvm-nm -am %t/bin/with_a | FileCheck --check-prefix=NM_WITH_A %s
+# RUN: llvm-nm -am %t/bin/with_a | FileCheck --check-prefix=NM_WITH_A_BAD %s
+
+# NM_WITH_A:           [[P_ADDR:[0-9a-f]+]] (__TEXT,__const) weak external _placeholder_int
+# NM_WITH_A:           [[A_ADDR:[0-9a-f]+]] (__TEXT,__const) external _strong_a
+# NM_WITH_A:           [[A_ADDR]]           (__TEXT,__const) external _weak_a
+# NM_WITH_A:           [[P_ADDR]]           (__TEXT,__const) weak external _weak_b
+
+# --- Addresses of _placeholder_int and _strong_a must not match.
+# NM_WITH_A_BAD:       [[P_ADDR:[0-9a-f]+]] (__TEXT,__const) weak external _placeholder_int
+# NM_WITH_A_BAD-NOT:   [[P_ADDR]]           (__TEXT,__const) external _strong_a
+
+# --- Test Case 3: Override weak_b
+# RUN: %lld %t/weak.o %t/strong_b.o -o %t/bin/with_b -e _s
+# RUN: llvm-nm -am %t/bin/with_b | FileCheck --check-prefix=NM_WITH_B %s
+# RUN: llvm-nm -am %t/bin/with_b | FileCheck --check-prefix=NM_WITH_B_BAD %s
+
+# NM_WITH_B:           [[P_ADDR:[0-9a-f]+]] (__TEXT,__const) weak external _placeholder_int
+# NM_WITH_B:           [[B_ADDR:[0-9a-f]+]] (__TEXT,__const) external _strong_b
+# NM_WITH_B:           [[P_ADDR]]           (__TEXT,__const) weak external _weak_a
+# NM_WITH_B:           [[B_ADDR]]           (__TEXT,__const) external _weak_b
+
+# --- Addresses of _placeholder_int and _strong_a must not match.
+# NM_WITH_B_BAD:       [[P_ADDR:[0-9a-f]+]] (__TEXT,__const) weak external _placeholder_int
+# NM_WITH_B_BAD-NOT:   [[P_ADDR]]           (__TEXT,__const) external _strong_b
+
+# --- Test Case 4: Override weak_a and weak_b
+# RUN: %lld %t/weak.o %t/strong_a.o %t/strong_b.o -o %t/bin/with_ab -e _s
+# RUN: llvm-nm -am %t/bin/with_ab | FileCheck --check-prefix=NM_WITH_AB %s
+# RUN: llvm-nm -am %t/bin/with_ab | FileCheck --check-prefix=NM_WITH_AB_BAD %s
+
+# NM_WITH_AB:          [[P_ADDR:[0-9a-f]+]] (__TEXT,__const) weak external _placeholder_int
+# NM_WITH_AB:          [[A_ADDR:[0-9a-f]+]] (__TEXT,__const) external _strong_a
+# NM_WITH_AB:          [[B_ADDR:[0-9a-f]+]] (__TEXT,__const) external _strong_b
+# NM_WITH_AB:          [[A_ADDR]]           (__TEXT,__const) external _weak_a
+# NM_WITH_AB:          [[B_ADDR]]           (__TEXT,__const) external _weak_b
+
+# --- Addresses of _placeholder_int, _strong_a, and _strong_b must all be distinct
+# NM_WITH_AB_BAD:      [[P_ADDR:[0-9a-f]+]] (__TEXT,__const) weak external _placeholder_int
+# NM_WITH_AB_BAD-NOT:  [[P_ADDR]]           (__TEXT,__const) external _strong_a
+# NM_WITH_AB_BAD-NOT:  [[P_ADDR]]           (__TEXT,__const) external _strong_b
+
+#--- weak.s
+.section __TEXT,__const
+.globl _placeholder_int
+.weak_definition _placeholder_int
+_placeholder_int:
+ .long 0
+
+.globl _weak_a
+.set _weak_a, _placeholder_int
+.weak_definition _weak_a
+
+.globl _weak_b
+.set _weak_b, _placeholder_int
+.weak_definition _weak_b
+
+.globl _s
+_s:
+ .quad _weak_a
+ .quad _weak_b
+
+#--- strong_a.s
+.section __TEXT,__const
+.globl _strong_a
+_strong_a:
+ .long 1
+
+.globl _weak_a
+_weak_a = _strong_a
+
+#--- strong_b.s
+.section __TEXT,__const
+.globl _strong_b
+_strong_b:
+ .long 2
+
+.globl _weak_b
+_weak_b = _strong_b