From 50dfba6905a4047b1ad255daab69e50877a1b3cd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Erik=20Fr=C3=B6jdh?= <erik.frojdh@gmail.com>
Date: Mon, 11 May 2026 16:51:11 +0200
Subject: [PATCH] rewriting receiver using sigwait

---
 slsReceiverSoftware/src/MultiReceiverApp.cpp | 44 +++++++++-----------
 slsReceiverSoftware/src/ReceiverApp.cpp      | 35 +++++++---------
 2 files changed, 36 insertions(+), 43 deletions(-)

diff --git a/slsReceiverSoftware/src/MultiReceiverApp.cpp b/slsReceiverSoftware/src/MultiReceiverApp.cpp
index ad6b869ca..51c206907 100644
--- a/slsReceiverSoftware/src/MultiReceiverApp.cpp
+++ b/slsReceiverSoftware/src/MultiReceiverApp.cpp
@@ -13,7 +13,7 @@
 
 #include <csignal> //SIGINT
 #include <cstring>
-#include <semaphore.h>
+#include <pthread.h>
 #include <sys/wait.h> //wait
 #include <unistd.h>
 
@@ -125,18 +125,6 @@ void GetData(slsDetectorDefs::sls_receiver_header &header,
     // imageSize = 26000;
 }
 
-sem_t semaphore;
-
-/**
- * Control+C Interrupt Handler
- * to let all the processes know to exit properly
- * All child processes will call the handler (parent process set to ignore)
- */
-void sigInterruptHandler(int signal) {
-    (void)signal; // suppress unused warning if needed
-    sem_post(&semaphore);
-}
-
 int main(int argc, char *argv[]) {
 
     CommandLineOptions cli(AppType::MultiReceiver);
@@ -154,13 +142,20 @@ int main(int argc, char *argv[]) {
     LOG(sls::logINFOBLUE) << "Current Process [ Tid: " << sls::getThreadId()
                           << ']';
 
-    // close files on ctrl+c
-    sls::setupSignalHandler(SIGINT, sigInterruptHandler);
+    // Block SIGINT before fork() so every child inherits the block. Each
+    // child waits for SIGINT synchronously via sigwait() instead of using a
+    // signal handler that posts to a semaphore. This avoids relying on
+    // sem_init() on unnamed semaphores, which is unimplemented on macOS.
+    sigset_t sigset;
+    sigemptyset(&sigset);
+    sigaddset(&sigset, SIGINT);
+    if (pthread_sigmask(SIG_BLOCK, &sigset, nullptr) != 0) {
+        LOG(sls::logERROR) << "Could not block SIGINT";
+        return EXIT_FAILURE;
+    }
     // handle locally on socket crash
     sls::setupSignalHandler(SIGPIPE, SIG_IGN);
 
-    sem_init(&semaphore, 1, 0);
-
     /** - loop over receivers */
     for (int i = 0; i < m.numReceivers; ++i) {
 
@@ -207,14 +202,15 @@ int main(int argc, char *argv[]) {
                 }
 
                 /**	- as long as no Ctrl+C */
-                // each child process gets a copy of the semaphore
-                sem_wait(&semaphore);
-                sem_destroy(&semaphore);
+                // SIGINT is blocked in this child (inherited from parent);
+                // sigwait atomically waits for it without competing with any
+                // signal handler.
+                int sig = 0;
+                sigwait(&sigset, &sig);
                 LOG(sls::logINFOBLUE) << "Exiting Child Process [ Tid: "
                                       << sls::getThreadId() << ']';
                 exit(EXIT_SUCCESS);
             } catch (...) {
-                sem_destroy(&semaphore);
                 LOG(sls::logINFOBLUE) << "Exiting Child Process [ Tid: "
                                       << sls::getThreadId() << " ]";
                 exit(EXIT_FAILURE);
@@ -222,9 +218,9 @@ int main(int argc, char *argv[]) {
         }
     }
 
-    /** - Parent process ignores SIGINT and waits for all the child processes to
-     * handle the signal */
-    sls::setupSignalHandler(SIGINT, SIG_IGN);
+    /** - Parent process keeps SIGINT blocked (set above before fork) so it is
+     * never delivered here while waitpid() runs. Each child handles SIGINT
+     * via sigwait(). */
 
     /** - Print Ready and Instructions how to exit */
     std::cout << "Ready ... \n";
diff --git a/slsReceiverSoftware/src/ReceiverApp.cpp b/slsReceiverSoftware/src/ReceiverApp.cpp
index b6d38689d..72b388b0c 100644
--- a/slsReceiverSoftware/src/ReceiverApp.cpp
+++ b/slsReceiverSoftware/src/ReceiverApp.cpp
@@ -11,20 +11,9 @@
 #include "sls/sls_detector_defs.h"
 
 #include <csignal> //SIGINT
-#include <semaphore.h>
+#include <pthread.h>
 #include <unistd.h>
 
-sem_t semaphore;
-
-/**
- * Control+C Interrupt Handler
- * to let all the other process know to exit properly
- */
-void sigInterruptHandler(int signal) {
-    (void)signal; // suppress unused warning if needed
-    sem_post(&semaphore);
-}
-
 int main(int argc, char *argv[]) {
 
     CommandLineOptions cli(AppType::SingleReceiver);
@@ -42,20 +31,28 @@ int main(int argc, char *argv[]) {
     LOG(sls::logINFOBLUE) << "Current Process [ Tid: " << sls::getThreadId()
                           << " ]";
 
-    // close files on ctrl+c
-    sls::setupSignalHandler(SIGINT, sigInterruptHandler);
+    // Block SIGINT on this thread before any other thread is created so that
+    // every thread spawned by Receiver inherits the block. We wait for the
+    // signal synchronously with sigwait() further down. This avoids needing a
+    // signal handler that posts to a semaphore, which is not portable to
+    // macOS (sem_init on unnamed semaphores is unimplemented there).
+    sigset_t sigset;
+    sigemptyset(&sigset);
+    sigaddset(&sigset, SIGINT);
+    if (pthread_sigmask(SIG_BLOCK, &sigset, nullptr) != 0) {
+        LOG(sls::logERROR) << "Could not block SIGINT";
+        return EXIT_FAILURE;
+    }
+
     // handle locally on socket crash
     sls::setupSignalHandler(SIGPIPE, SIG_IGN);
 
-    sem_init(&semaphore, 1, 0);
-
     try {
         sls::Receiver r(o.port);
         LOG(sls::logINFO) << "[ Press \'Ctrl+c\' to exit ]";
-        sem_wait(&semaphore);
-        sem_destroy(&semaphore);
+        int sig = 0;
+        sigwait(&sigset, &sig);
     } catch (...) {
-        sem_destroy(&semaphore);
         LOG(sls::logINFOBLUE)
             << "Exiting [ Tid: " << sls::getThreadId() << " ]";
         throw;