diff --git a/core/build.gradle.kts b/core/build.gradle.kts
index cd48963..d30d26c 100644
--- a/core/build.gradle.kts
+++ b/core/build.gradle.kts
@@ -25,15 +25,18 @@ kotlin {
                     create("barrier") {
                         defFile(project.file("src/nativeInterop/barrier.def"))
                         headers(project.file("src/nativeInterop/barrier.h"))
+                        compilerOpts.addAll(listOf("-Wall", "-Werror"))
                     }
                     if (affinitySupported) {
                         create("affinity") {
                             defFile(project.file("src/nativeInterop/kaffinity.def"))
                             compilerOpts.add("-D_GNU_SOURCE")
+                            compilerOpts.addAll(listOf("-Wall", "-Werror"))
                         }
                     }
                     create("kpthread") {
                         defFile(project.file("src/nativeInterop/kpthread.def"))
+                        compilerOpts.addAll(listOf("-Wall", "-Werror"))
                     }
                 }
             }
diff --git a/core/src/commonMain/kotlin/org/jetbrains/litmuskt/ThreadlikeRunner.kt b/core/src/commonMain/kotlin/org/jetbrains/litmuskt/ThreadlikeRunner.kt
index 25e8b6f..78c8948 100644
--- a/core/src/commonMain/kotlin/org/jetbrains/litmuskt/ThreadlikeRunner.kt
+++ b/core/src/commonMain/kotlin/org/jetbrains/litmuskt/ThreadlikeRunner.kt
@@ -27,13 +27,6 @@ abstract class ThreadlikeRunner : LitmusRunner() {
     ): () -> LitmusResult {
 
         val threads = List(test.threadCount) { threadlikeProducer() }
-        affinityMap?.let { map ->
-            affinityManager?.apply {
-                for ((i, t) in threads.withIndex()) {
-                    setAffinityAndCheck(t, map.allowedCores(i))
-                }
-            }
-        }
 
         val barrier = barrierProducer(test.threadCount)
         val contexts = List(threads.size) { i ->
@@ -44,6 +37,15 @@ abstract class ThreadlikeRunner : LitmusRunner() {
             thread.start(context, ::threadFunction)
         }
 
+        // cannot set affinity before thread is started (because pthread_create has not been called yet)
+        affinityMap?.let { map ->
+            affinityManager?.apply {
+                for ((i, t) in threads.withIndex()) {
+                    setAffinityAndCheck(t, map.allowedCores(i))
+                }
+            }
+        }
+
         return {
             futures.forEach { it.await() } // await all results
             threads.forEach { it.dispose() } // stop all "threads"
diff --git a/core/src/nativeInterop/kaffinity.def b/core/src/nativeInterop/kaffinity.def
index 5a4a8ba..acad8c0 100644
--- a/core/src/nativeInterop/kaffinity.def
+++ b/core/src/nativeInterop/kaffinity.def
@@ -3,10 +3,12 @@
 #include <pthread.h>
 
 int set_affinity(void* thread, cpu_set_t* set) {
-    return pthread_setaffinity_np(*((pthread_t*) thread), sizeof(*set), set);
+    pthread_t pthread = *((pthread_t*) thread);
+    return pthread_setaffinity_np(pthread, sizeof(*set), set);
 }
 int get_affinity(void* thread, cpu_set_t* set) {
-    return pthread_getaffinity_np(*((pthread_t*) thread), sizeof(*set), set);
+    pthread_t pthread = *((pthread_t*) thread);
+    return pthread_getaffinity_np(pthread, sizeof(*set), set);
 }
 
 void cpu_zero(cpu_set_t* set) {
@@ -16,7 +18,7 @@ void cpu_set(int cpu, cpu_set_t* set) {
     CPU_SET(cpu, set);
 }
 int cpu_isset(int cpu, cpu_set_t* set) {
-    CPU_ISSET(cpu, set);
+    return CPU_ISSET(cpu, set);
 }
 int cpu_setsize() {
     return CPU_SETSIZE;