[lld-macho] Don't double emit reexported libraries

[speednoisemovement]

When a library is specified with both -l and -reexport_libraries, lld will emit two load commands for it, in contrast with ld64.
In an upcoming version of macOS, this fails dyld validation; see https://crbug.com/404905688

[llvmbot]

@llvm/pr-subscribers-lld

@llvm/pr-subscribers-lld-macho

Author: Leonard Grey (speednoisemovement)

Changes

When a library is specified with both -l and -reexport_libraries, lld will emit two load commands for it, in contrast with ld64.
In an upcoming version of macOS, this fails dyld validation; see https://crbug.com/404905688

---

Full diff: https://github.com/llvm/llvm-project/pull/132275.diff

2 Files Affected:

• (modified) lld/MachO/Writer.cpp (+11-9)
• (modified) lld/test/MachO/sub-library.s (+11)

diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
index d9856a46e8cb8..7a5fdcd2276a5 100644
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -938,17 +938,19 @@ template <class LP> void Writer::createLoadCommands() {
     }
 
     ordinal = dylibFile->ordinal = dylibOrdinal++;
-    LoadCommandType lcType =
-        dylibFile->forceWeakImport || dylibFile->refState == RefState::Weak
-            ? LC_LOAD_WEAK_DYLIB
-            : LC_LOAD_DYLIB;
+    LoadCommandType lcType = LC_LOAD_DYLIB;
+    if (dylibFile->reexport) {
+      if (dylibFile->forceWeakImport)
+        warn(path::filename(dylibFile->getName()) + " is re-exported so cannot be weak-linked");
+
+      lcType = LC_REEXPORT_DYLIB;
+    } else if (dylibFile->forceWeakImport || dylibFile->refState == RefState::Weak) {
+      lcType = LC_LOAD_WEAK_DYLIB;
+    }
     in.header->addLoadCommand(make<LCDylib>(lcType, dylibFile->installName,
-                                            dylibFile->compatibilityVersion,
-                                            dylibFile->currentVersion));
+                                        dylibFile->compatibilityVersion,
+                                        dylibFile->currentVersion));
 
-    if (dylibFile->reexport)
-      in.header->addLoadCommand(
-          make<LCDylib>(LC_REEXPORT_DYLIB, dylibFile->installName));
   }
 
   for (const auto &dyldEnv : config->dyldEnvs)
diff --git a/lld/test/MachO/sub-library.s b/lld/test/MachO/sub-library.s
index ed0a96aa58f90..d799b8d54c01a 100644
--- a/lld/test/MachO/sub-library.s
+++ b/lld/test/MachO/sub-library.s
@@ -42,6 +42,17 @@
 # REEXPORT-HEADERS-NOT: Load command
 # REEXPORT-HEADERS:     name    [[PATH]]
 
+## Check that specifying a library both with `l` and `reexport_library`
+## doesn't emit two load commands.
+# RUN: %lld -dylib -reexport_library %t/libgoodbye.dylib \
+# RUN:   -L%t -lgoodbye %t/libsuper.o -o %t/libsuper.dylib
+# RUN: llvm-otool -L %t/libsuper.dylib | FileCheck %s \
+# RUN:   --check-prefix=REEXPORT-DOUBLE -DPATH=%t/libgoodbye.dylib
+
+# REEXPORT-DOUBLE: [[PATH]]
+# REEXPORT-DOUBLE-SAME: reexport
+# REEXPORT-DOUBLE-NOT: [[PATH]]
+
 # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t/sub-library.o
 # RUN: %lld -o %t/sub-library -L%t -lsuper %t/sub-library.o
 

[github-actions]

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