[Mach-O] Add -hidden-l

macho/cmdline.cc

@@ -41,6 +41,7 @@ Options:
   -headerpad_max_install_names
                               Allocate MAXPATHLEN byte padding after load commands
   -help                       Report usage information
+  -hidden-l<LIB>
   -install_name <NAME>
   -l<LIB>                     Search for a given library
   -lto_library <FILE>         Ignored
@@ -257,6 +258,9 @@ std::vector<std::string> parse_nonpositional_args(Context<E> &ctx) {
     } else if (read_arg("-macos_version_min")) {
       ctx.arg.platform = PLATFORM_MACOS;
       ctx.arg.platform_min_version = parse_version(ctx, arg);
+    } else if (read_joined("-hidden-l")) {
+      remaining.push_back("-hidden-l");
+      remaining.push_back(std::string(arg));
     } else if (read_arg("-install_name")) {
       ctx.arg.install_name = arg;
     } else if (read_joined("-l")) {

macho/input-files.cc

@@ -21,6 +21,7 @@ ObjectFile<E>::create(Context<E> &ctx, MappedFile<Context<E>> *mf,
   obj->mf = mf;
   obj->archive_name = archive_name;
   obj->is_alive = archive_name.empty() || ctx.all_load;
+  obj->is_hidden = ctx.hidden_l;
   ctx.obj_pool.emplace_back(obj);
   return obj;
 };
@@ -398,7 +399,7 @@ void ObjectFile<E>::resolve_symbols(Context<E> &ctx) {
 
     if (get_rank(this, msym.is_common(), false) < get_rank(sym)) {
       sym.file = this;
-      sym.is_extern = msym.ext;
+      sym.is_extern = (msym.ext && !this->is_hidden);
       sym.is_imported = false;
 
       switch (msym.type) {

macho/main.cc

@@ -358,6 +358,13 @@ read_filelist(Context<E> &ctx, std::string arg) {
 
 template <typename E>
 static void read_input_files(Context<E> &ctx, std::span<std::string> args) {
+  auto must_find_library = [&](std::string arg) {
+    MappedFile<Context<E>> *mf = find_library(ctx, arg);
+    if (!mf)
+      Fatal(ctx) << "library not found: -l" << arg;
+    return mf;
+  };
+
   while (!args.empty()) {
     const std::string &arg = args[0];
     args = args.subspan(1);
@@ -383,11 +390,17 @@ static void read_input_files(Context<E> &ctx, std::span<std::string> args) {
     } else if (arg == "-framework" || arg == "-needed_framework") {
       read_file(ctx, find_framework(ctx, args[0]), arg == "-needed_framework");
       args = args.subspan(1);
-    } else if (arg == "-l" || arg == "-needed-l") {
+    } else if (arg == "-l") {
-      MappedFile<Context<E>> *mf = find_library(ctx, args[0]);
+      read_file(ctx, must_find_library(args[0]), false);
-      if (!mf)
+      args = args.subspan(1);
-        Fatal(ctx) << "library not found: -l" << args[0];
+    } else if (arg == "-needed-l") {
-      read_file(ctx, mf, arg == "-needed-l");
+      read_file(ctx, must_find_library(args[0]), true);
+      args = args.subspan(1);
+    } else if (arg == "-hidden-l") {
+      bool orig = ctx.hidden_l;
+      ctx.hidden_l = true;
+      read_file(ctx, must_find_library(args[0]), arg == "-needed-l");
+      ctx.hidden_l = orig;
       args = args.subspan(1);
     } else {
       read_file(ctx, MappedFile<Context<E>>::must_open(ctx, arg));

macho/mold.h

@@ -88,6 +88,7 @@ public:
   i64 priority = 0;
   std::atomic_bool is_alive = false;
   bool is_dylib = false;
+  bool is_hidden = false;
   std::string archive_name;
 
 protected:
@@ -824,6 +825,7 @@ struct Context {
   std::vector<std::string_view> cmdline_args;
   u32 output_type = MH_EXECUTE;
   bool all_load = false;
+  bool hidden_l = false;
 
   bool has_error = false;
 

test/macho/hidden-l.sh

@@ -0,0 +1,47 @@
+#!/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 -c -o $t/a.o -fPIC -xc -
+void foo() {}
+EOF
+
+rm -f $t/libfoo.a
+ar rcu $t/libfoo.a $t/a.o
+
+cat <<EOF | $CC -c -o $t/b.o -fPIC -xc -
+void bar() {}
+EOF
+
+rm -f $t/libbar.a
+ar rcu $t/libbar.a $t/b.o
+
+cat <<EOF | $CC -c -o $t/c.o -xc -
+void foo();
+void bar();
+
+void baz() {
+  foo();
+  bar();
+}
+EOF
+
+clang --ld-path=./ld64 -shared -o $t/f.dylib $t/c.o -L$t -lfoo -Wl,-hidden-lbar
+
+nm -g $t/f.dylib > $t/log
+grep -q ' _foo$' $t/log
+! grep -q ' _bar$' $t/log || false
+grep -q ' _baz$' $t/log
+
+echo OK