From a116f08acba19a19975df742a12ba5a9a1400484 Mon Sep 17 00:00:00 2001
From: Andreas Kling <andreas@ladybird.org>
Date: Tue, 24 Feb 2026 21:26:39 +0100
Subject: [PATCH] LibThreading: Allow configuring thread stack size

Add set_stack_size() to Threading::Thread and use pthread_attr_t to
apply it in start().
---
 Libraries/LibThreading/Thread.cpp | 14 ++++++++++++--
 Libraries/LibThreading/Thread.h   |  3 +++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/Libraries/LibThreading/Thread.cpp b/Libraries/LibThreading/Thread.cpp
index 3e9cfd2cf9..f64fe604ef 100644
--- a/Libraries/LibThreading/Thread.cpp
+++ b/Libraries/LibThreading/Thread.cpp
@@ -70,10 +70,17 @@ void Thread::start()
     // Set this first so that the other thread starts out seeing m_state == Running.
     m_state = Threading::ThreadState::Running;
 
+    pthread_attr_t attr;
+    pthread_attr_t* attr_ptr = nullptr;
+    if (m_stack_size > 0) {
+        pthread_attr_init(&attr);
+        pthread_attr_setstacksize(&attr, m_stack_size);
+        attr_ptr = &attr;
+    }
+
     int rc = pthread_create(
         &m_tid,
-        // FIXME: Use pthread_attr_t to start a thread detached if that was requested by the user before the call to start().
-        nullptr,
+        attr_ptr,
         [](void* arg) -> void* {
             auto self = adopt_ref(*static_cast<Thread*>(arg));
 
@@ -112,6 +119,9 @@ void Thread::start()
         },
         &NonnullRefPtr(*this).leak_ref());
 
+    if (attr_ptr)
+        pthread_attr_destroy(attr_ptr);
+
     VERIFY(rc == 0);
 }
 
diff --git a/Libraries/LibThreading/Thread.h b/Libraries/LibThreading/Thread.h
index bbc0b38c53..3b4951cd10 100644
--- a/Libraries/LibThreading/Thread.h
+++ b/Libraries/LibThreading/Thread.h
@@ -59,6 +59,8 @@ public:
     ErrorOr<void> set_priority(int priority);
     ErrorOr<int> get_priority() const;
 
+    void set_stack_size(size_t size) { m_stack_size = size; }
+
     // Only callable in the Startable state.
     void start();
     // Only callable in the Running state.
@@ -81,6 +83,7 @@ private:
     pthread_t m_tid {};
     ByteString m_thread_name;
     Atomic<ThreadState> m_state { ThreadState::Startable };
+    size_t m_stack_size { 0 };
 };
 
 template<typename T>