From c6b54532e9519f121d4683e553eacafdf2598fad Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Thu, 4 Jul 2024 16:17:25 +0900
Subject: [PATCH] Refactor

---
 elf/main.cc       |  8 +++-----
 elf/mold.h        |  3 ++-
 elf/subprocess.cc | 18 ++++++++++++------
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/elf/main.cc b/elf/main.cc
index bb329790..c9ace457 100644
--- a/elf/main.cc
+++ b/elf/main.cc
@@ -375,11 +375,9 @@ int elf_main(int argc, char **argv) {
                  << ": " << errno_string();
 
   // Fork a subprocess unless --no-fork is given.
-  std::function<void()> on_complete;
-
 #if !defined(_WIN32) && !defined(__APPLE__)
   if (ctx.arg.fork)
-    on_complete = fork_child();
+    fork_child();
 #endif
 
   acquire_global_lock();
@@ -706,8 +704,8 @@ int elf_main(int argc, char **argv) {
   std::cout << std::flush;
   std::cerr << std::flush;
 
-  if (on_complete)
-    on_complete();
+  if (ctx.arg.fork)
+    notify_parent();
 
   release_global_lock();
 
diff --git a/elf/mold.h b/elf/mold.h
index bba6f235..1e8d3bc6 100644
--- a/elf/mold.h
+++ b/elf/mold.h
@@ -1367,7 +1367,8 @@ void print_map(Context<E> &ctx);
 // subprocess.cc
 //
 
-std::function<void()> fork_child();
+void fork_child();
+void notify_parent();
 
 template <typename E>
 [[noreturn]]
diff --git a/elf/subprocess.cc b/elf/subprocess.cc
index 51be8972..b8eceda5 100644
--- a/elf/subprocess.cc
+++ b/elf/subprocess.cc
@@ -14,10 +14,12 @@
 namespace mold::elf {
 
 #ifdef MOLD_X86_64
+static int pipe_write_fd = -1;
+
 // Exiting from a program with large memory usage is slow --
 // it may take a few hundred milliseconds. To hide the latency,
 // we fork a child and let it do the actual linking work.
-std::function<void()> fork_child() {
+void fork_child() {
   int pipefd[2];
   if (pipe(pipefd) == -1) {
     perror("pipe");
@@ -50,12 +52,16 @@ std::function<void()> fork_child() {
 
   // Child
   close(pipefd[0]);
+  pipe_write_fd = pipefd[1];
+}
 
-  return [=] {
-    char buf[] = {1};
-    [[maybe_unused]] int n = write(pipefd[1], buf, 1);
-    assert(n == 1);
-  };
+void notify_parent() {
+  if (pipe_write_fd == -1)
+    return;
+
+  char buf[] = {1};
+  [[maybe_unused]] int n = write(pipe_write_fd, buf, 1);
+  assert(n == 1);
 }
 #endif