[Mach-O] Add -reexport-l

macho/cmdline.cc

@@ -71,6 +71,7 @@ Options:
   -platform_version <PLATFORM> <MIN_VERSION> <SDK_VERSION>
                               Set platform, platform version and SDK version
   -random_uuid                Generate a random LC_UUID load command
+  -reexport-l<LIB>            Search for a given library
   -rpath <PATH>               Add PATH to the runpath search path list
   -search_dylibs_first
   -search_paths_first
@@ -372,6 +373,9 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
       ctx.arg.quick_exit = false;
     } else if (read_flag("-random_uuid")) {
       ctx.arg.uuid = UUID_RANDOM;
+    } else if (read_joined("-reexport-l")) {
+      remaining.push_back("-reexport-l");
+      remaining.push_back(std::string(arg));
     } else if (read_arg("-rpath")) {
       ctx.arg.rpath.push_back(std::string(arg));
     } else if (read_flag("-search_paths_first")) {

macho/input-files.cc

@@ -738,6 +738,7 @@ DylibFile<E> *DylibFile<E>::create(Context<E> &ctx, MappedFile<Context<E>> *mf)
   DylibFile<E> *dylib = new DylibFile<E>(mf);
   dylib->is_alive = (ctx.needed_l || !ctx.arg.dead_strip_dylibs);
   dylib->is_weak = ctx.weak_l;
+  dylib->is_reexported = ctx.reexport_l;
   ctx.dylib_pool.emplace_back(dylib);
 
   switch (get_file_type(mf)) {

macho/main.cc

@@ -726,6 +726,9 @@ static void read_input_files(Context<E> &ctx, std::span<std::string> args) {
     } else if (opt == "-weak-l") {
       ctx.weak_l = true;
       read_file(ctx, must_find_library(arg));
+    } else if (opt == "-reexport-l") {
+      ctx.reexport_l = true;
+      read_file(ctx, must_find_library(arg));
     } else {
       unreachable();
     }
@@ -733,6 +736,7 @@ static void read_input_files(Context<E> &ctx, std::span<std::string> args) {
     ctx.needed_l = false;
     ctx.hidden_l = false;
     ctx.weak_l = false;
+    ctx.reexport_l = false;
   }
 
   // An object file can contain linker directives to load other object

macho/mold.h

@@ -166,6 +166,7 @@ public:
   std::string_view install_name;
   i64 dylib_idx = 0;
   std::vector<std::string_view> reexported_libs;
+  bool is_reexported = false;
 
 private:
   void read_trie(Context<E> &ctx, u8 *start, i64 offset = 0,
@@ -883,6 +884,7 @@ struct Context {
   bool needed_l = false;
   bool hidden_l = false;
   bool weak_l = false;
+  bool reexport_l = false;
   std::unordered_set<std::string_view> loaded_archives;
 
   u8 uuid[16] = {};

macho/output-chunks.cc

@@ -155,7 +155,13 @@ create_load_dylib_cmd(Context<E> &ctx, DylibFile<E> &dylib) {
   std::vector<u8> buf(align_to(size, 8));
   DylibCommand &cmd = *(DylibCommand *)buf.data();
 
-  cmd.cmd = (dylib.is_weak ? LC_LOAD_WEAK_DYLIB : LC_LOAD_DYLIB);
+  if (dylib.is_reexported)
+    cmd.cmd = LC_REEXPORT_DYLIB;
+  else if (dylib.is_weak)
+    cmd.cmd = LC_LOAD_WEAK_DYLIB;
+  else
+    cmd.cmd = LC_LOAD_DYLIB;
+
   cmd.cmdsize = buf.size();
   cmd.nameoff = sizeof(cmd);
   cmd.timestamp = 2;

test/macho/reexport-l.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+export LC_ALL=C
+set -e
+CC="${TEST_CC:-cc}"
+CXX="${TEST_CXX:-c++}"
+GCC="${TEST_GCC:-gcc}"
+GXX="${TEST_GXX:-g++}"
+OBJDUMP="${OBJDUMP:-objdump}"
+MACHINE="${MACHINE:-$(uname -m)}"
+testname=$(basename "$0" .sh)
+echo -n "Testing $testname ... "
+cd "$(dirname "$0")"/../..
+t=out/test/macho/$testname
+mkdir -p $t
+
+cat <<EOF | $CC -o $t/a.o -shared -xc -
+void foo() {}
+EOF
+
+clang --ld-path=./ld64 -shared -o $t/libfoo.dylib $t/a.o
+
+cat <<EOF | $CC -o $t/b.o -c -xc -
+void bar() {}
+EOF
+
+clang -shared -o $t/libbar.dylib $t/b.o -L$t -Wl,-reexport-lfoo
+
+objdump --macho --dylibs-used $t/libbar.dylib | grep -q 'libfoo.*reexport'
+
+echo OK