From 0624541e01216c65dbc13b01aedef2e24d50b7df Mon Sep 17 00:00:00 2001
From: tnagler <thomas.nagler@tum.de>
Date: Mon, 15 Sep 2025 23:42:47 +0200
Subject: [PATCH 1/2] fix early termination issue

---
 inst/include/RcppThread/ThreadPool.hpp | 14 +++++++++++---
 inst/include/RcppThread/quickpool.hpp  | 10 ++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/inst/include/RcppThread/ThreadPool.hpp b/inst/include/RcppThread/ThreadPool.hpp
index 340a9a6..58cb010 100644
--- a/inst/include/RcppThread/ThreadPool.hpp
+++ b/inst/include/RcppThread/ThreadPool.hpp
@@ -167,7 +167,7 @@ ThreadPool::map(F&& f, I&& items)
 //! The parallel equivalent is given by:
 //! ```
 //! ThreadPool pool(2);
-//! pool.forIndex(0, 10, [&] (size_t i) {
+//! pool.parallelFor(0, 10, [&] (size_t i) {
 //!     x[i] = i;
 //! });
 //! ```
@@ -228,6 +228,11 @@ ThreadPool::parallelFor(int begin, int end, F f, size_t nBatches)
 //! ```
 //! **Caution**: if the iterations are not independent from another,
 //! the tasks need to be synchronized manually (e.g., using mutexes).
+//!
+//' The worker callable `f(i)` should be **interrupt-friendly**:
+//' insert `RcppThread::isInterrupted()` checks at a reasonable cadence and
+//' **return early** when it is true. On user interrupt, RcppThread waits for
+//' running tasks to reach a check point or finish, and then unwinds to R.
 template<class F, class I>
 inline void
 ThreadPool::parallelForEach(I& items, F f, size_t nBatches)
@@ -248,8 +253,11 @@ ThreadPool::wait()
         pool_->wait(100);
         Rcout << "";
         Rcerr << "";
-        checkUserInterrupt();
-
+        try {
+            checkUserInterrupt();
+        } catch (const UserInterruptException& err) {
+            pool_->stop_and_reset();
+        }
     } while (!pool_->done());
     Rcout << "";
     Rcerr << "";
diff --git a/inst/include/RcppThread/quickpool.hpp b/inst/include/RcppThread/quickpool.hpp
index 1507e14..264c035 100644
--- a/inst/include/RcppThread/quickpool.hpp
+++ b/inst/include/RcppThread/quickpool.hpp
@@ -926,6 +926,15 @@ class ThreadPool
     //! @param millis if > 0: stops waiting after millis ms.
     void wait(size_t millis = 0) { task_manager_.wait_for_finish(millis); }
 
+    //! @brief Stops the pool, waits for all tasks to finish, resets to neutral 
+    // state, and rethrows an exception if one is pending.
+    void stop_and_reset() 
+    { 
+        task_manager_.report_fail(std::current_exception());
+        task_manager_.wait_for_finish();
+        task_manager_.rethrow_exception();
+    }
+
     //! @brief checks whether all jobs are done.
     bool done() const { return task_manager_.done(); }
 
@@ -939,6 +948,7 @@ class ThreadPool
     static void operator delete(void* ptr) { mem::aligned::free(ptr); }
 
   private:
+  
     //! joins all worker threads.
     void join_threads()
     {

From 5524619f23cce19baf7c76ce3b9fdd9064c57cfa Mon Sep 17 00:00:00 2001
From: tnagler <thomas.nagler@tum.de>
Date: Wed, 14 Jan 2026 16:09:53 +0100
Subject: [PATCH 2/2] print with R_ToplevelExec

---
 inst/include/RcppThread/RMonitor.hpp | 48 ++++++++++++++++++----------
 1 file changed, 32 insertions(+), 16 deletions(-)

diff --git a/inst/include/RcppThread/RMonitor.hpp b/inst/include/RcppThread/RMonitor.hpp
index 6b2a4fe..9b913de 100644
--- a/inst/include/RcppThread/RMonitor.hpp
+++ b/inst/include/RcppThread/RMonitor.hpp
@@ -90,17 +90,28 @@ class RMonitor {
     //! adds a printable version of `object` to a buffer for deferred printing.
     //! @param object a string or coercible object to print.
     template<class T>
-    void safelyPrint(const T& object)
-    {
+    void safelyPrint(const T& object, bool asErr = false) {
+      std::string to_print;
+      {
         std::lock_guard<std::mutex> lk(m_);
         msgs_ << object;
-        if ( calledFromMainThread() && (msgs_.str() != std::string("")) ) {
-            // release messages in buffer
-            Rprintf("%s", msgs_.str().c_str());
-            R_FlushConsole();
-            // clear message buffer
+        
+        if (calledFromMainThread()) {
+          to_print = msgs_.str();
+          if (!to_print.empty()) {
             msgs_.str("");
+            msgs_.clear();
+          }
         }
+      } // mutex released here, before touching R API
+    
+      if (!to_print.empty()) {
+        // Contain possible longjmp from Rgui/event loop
+        PrintData pd{&to_print};
+        void (*printfun)(void*) = asErr ? &printErr : &print;
+        Rboolean ok = R_ToplevelExec(printfun, &pd);
+        if (!ok) throw UserInterruptException();
+      }
     }
 
     //! prints `object` to R error stream íf called from main thread; otherwise
@@ -109,18 +120,23 @@ class RMonitor {
     template<class T>
     void safelyPrintErr(const T& object)
     {
-        std::lock_guard<std::mutex> lk(m_);
-        msgsErr_ << object;
-        if ( calledFromMainThread() && (msgsErr_.str() != std::string("")) ) {
-            // release messages in buffer
-            REprintf("%s", msgsErr_.str().c_str());
-            // R_FlushConsole();
-            // clear message buffer
-            msgsErr_.str("");
-        }
+        safelyPrint(object, true);
     }
 
 private:
+    struct PrintData { std::string* s; };
+
+    static void print(void* data) {
+      auto* pd = static_cast<PrintData*>(data);
+      Rprintf("%s", pd->s->c_str());
+      R_FlushConsole();
+    }
+
+    static void printErr(void* data) {
+      auto* pd = static_cast<PrintData*>(data);
+      REprintf("%s", pd->s->c_str());
+    }
+  
     //! Ctors declared private, to instantiate class use `::instance()`.
     RMonitor(void) : isInterrupted_(false) {}