From a48bd587f7d28ce71b8d7ba6f0fb6499072acf40 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Sun, 6 Jun 2021 16:57:19 -0400
Subject: [PATCH] [lld/mac] Implement support for searching dylibs with
 @executable_path/ in install name

Differential Revision: https://reviews.llvm.org/D103775
---
 lld/MachO/InputFiles.cpp                        | 10 +++++-
 lld/test/MachO/link-search-at-executable-path.s | 41 +++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 lld/test/MachO/link-search-at-executable-path.s

diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
index 288a3ac..ac34920 100644
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -760,7 +760,15 @@ DylibFile *findDylib(StringRef path, DylibFile *umbrella,
               resolveDylibPath((root + path).str()))
         return loadDylib(*dylibPath, umbrella);
 
-  // TODO: Expand @loader_path, @executable_path, @rpath etc, handle -dylib_path
+  // TODO: Expand @loader_path, @rpath etc, handle -dylib_file
+  SmallString<128> newPath;
+  if (config->outputType == MH_EXECUTE &&
+      path.consume_front("@executable_path/")) {
+    // ld64 allows overriding this with the undocumented flag -executable_path.
+    // lld doesn't currently implement that flag.
+    path::append(newPath, sys::path::parent_path(config->outputFile), path);
+    path = newPath;
+  }
 
   if (currentTopLevelTapi) {
     for (InterfaceFile &child :
diff --git a/lld/test/MachO/link-search-at-executable-path.s b/lld/test/MachO/link-search-at-executable-path.s
new file mode 100644
index 0000000..29f2ac8
--- /dev/null
+++ b/lld/test/MachO/link-search-at-executable-path.s
@@ -0,0 +1,41 @@
+# REQUIRES: x86
+
+# RUN: rm -rf %t; split-file %s %t
+# RUN: mkdir %t/subdir
+
+# RUN: llvm-mc -filetype obj -triple x86_64-apple-darwin %t/foo.s -o %t/foo.o
+# RUN: llvm-mc -filetype obj -triple x86_64-apple-darwin %t/bar.s -o %t/bar.o
+# RUN: llvm-mc -filetype obj -triple x86_64-apple-darwin %t/main.s -o %t/main.o
+
+# RUN: %lld -dylib -install_name @executable_path/libfoo.dylib %t/foo.o -o %t/subdir/libfoo.dylib
+
+# RUN: %lld -dylib -reexport_library %t/subdir/libfoo.dylib %t/bar.o -o %t/libbar.dylib
+
+## When linking executables, @executable_path/ in install_name should be replaced
+## by the path of the executable.
+# RUN: %lld -lSystem %t/main.o %t/libbar.dylib -o %t/subdir/test
+
+## This doesn't work for non-executables.
+# RUN: not %lld -dylib -lSystem %t/main.o %t/libbar.dylib -o %t/subdir/libtest.dylib 2>&1 | FileCheck --check-prefix=ERR %s
+
+## It also doesn't help if the needed reexport isn't next to the library.
+# RUN: not %lld -lSystem %t/main.o %t/libbar.dylib -o %t/test 2>&1 | FileCheck --check-prefix=ERR %s
+# ERR: error: unable to locate re-export with install name @executable_path/libfoo.dylib
+
+#--- foo.s
+.globl _foo
+_foo:
+  retq
+
+#--- bar.s
+.globl _bar
+_bar:
+  retq
+
+#--- main.s
+.section __TEXT,__text
+.global _main
+_main:
+  callq _foo
+  callq _bar
+  ret
-- 
2.7.4