Java directors - more generic thread name setting

Activated if a user sets SWIG_JAVA_USE_THREAD_NAME.
Implementations provided for linux/android/macos/unix.
A user's implementation will be used if SWIG_JAVA_GET_THREAD_NAME is
defined. It must implement the function:
  namespace Swig {
    SWIGINTERN int GetThreadName(char *name, size_t len);
  }

Examples/test-suite/director_thread.i

@@ -7,6 +7,11 @@
 %module(directors="1") director_thread
 #endif
 
+%begin %{
+#define SWIG_JAVA_USE_THREAD_NAME
+//#define DEBUG_DIRECTOR_THREAD_NAME
+%}
+
 %{
 #ifdef _WIN32
 #include <windows.h>
@@ -89,10 +94,23 @@ extern "C" {
         fprintf(stderr, "pthread_create failed in run()\n");
         assert(0);
       }
+      int setname = pthread_setname_np(thread, "MyThreadName");
+      if (setname != 0) {
+        fprintf(stderr, "pthread_setname_np failed in run()\n");
+        assert(0);
+      }
 %#endif
       MilliSecondSleep(500);
     }
-    
+
+    static bool namedThread() {
+%#ifdef _WIN32
+      return false;
+%#else
+      return true;
+%#endif
+    }
+
     virtual void do_foo() {
       val += 1;
     }

Examples/test-suite/java/director_thread_runme.java

@@ -30,6 +30,12 @@ class director_thread_Derived extends Foo {
   }
 
   public void do_foo() {
+    // Not all operating systems can name threads, so only test on those that can
+    if (Foo.namedThread()) {
+      String threadName = Thread.currentThread().getName();
+      if (!threadName.equals("MyThreadName"))
+        throw new RuntimeException("Unexpected thread name: " + threadName);
+    }
     setVal(getVal() - 1);
   }
 }

Lib/java/director.swg

@@ -5,20 +5,52 @@
  * methods can be called from C++.
  * ----------------------------------------------------------------------------- */
 
-#if defined(__ANDROID__)
+#if defined(DEBUG_DIRECTOR_OWNED) || defined(DEBUG_DIRECTOR_EXCEPTION) || defined(DEBUG_DIRECTOR_THREAD_NAME)
-#include <sys/prctl.h>
-#endif
-
-#if defined(DEBUG_DIRECTOR_OWNED) || defined(DEBUG_DIRECTOR_EXCEPTION)
-#if defined(__ANDROID__)
-#include <errno.h>
-#include <string.h>
-#endif
 #include <iostream>
 #endif
 
 #include <exception>
 
+#if defined(SWIG_JAVA_USE_THREAD_NAME)
+
+#if !defined(SWIG_JAVA_GET_THREAD_NAME)
+namespace Swig {
+  SWIGINTERN int GetThreadName(char *name, size_t len);
+}
+
+#if defined(__linux__)
+
+#include <sys/prctl.h>
+SWIGINTERN int Swig::GetThreadName(char *name, size_t len) {
+  (void)len;
+#if defined(PR_GET_NAME)
+  return prctl(PR_GET_NAME, (unsigned long)name, 0, 0, 0);
+#else
+  (void)name;
+  return 1;
+#endif
+}
+
+#elif defined(__unix__)
+
+#include <pthread.h>
+SWIGINTERN int Swig::GetThreadName(char *name, size_t len) {
+  return pthread_getname_np(pthread_self(), name, len);
+}
+
+#else
+
+SWIGINTERN int Swig::GetThreadName(char *name, size_t len) {
+  (void)len;
+  (void)name;
+  return 1;
+}
+#endif
+
+#endif
+
+#endif
+
 namespace Swig {
 
   /* Java object wrapper */
@@ -151,13 +183,14 @@ namespace Swig {
         args.version = JNI_VERSION_1_2;
         args.group = NULL;
         args.name = NULL;
-#if defined(__ANDROID__)
+#if defined(SWIG_JAVA_USE_THREAD_NAME)
         char thread_name[16];  // MAX_TASK_COMM_LEN=16 is hard-coded in the kernel.
-        if (prctl(PR_GET_NAME, (unsigned long)thread_name, 0, 0, 0) == 0) {
+        if (Swig::GetThreadName(thread_name, sizeof(thread_name)) == 0) {
           args.name = thread_name;
+#if defined(DEBUG_DIRECTOR_THREAD_NAME)
+          std::cout << "JNIEnvWrapper: thread name: " << thread_name << std::endl;
         } else {
-#if defined(DEBUG_DIRECTOR_OWNED) || defined(DEBUG_DIRECTOR_EXCEPTION)
+          std::cout << "JNIEnvWrapper: Couldn't set Java thread name" << std::endl;
-          std::cerr << "JNIEnvWrapper: Couldn't set thread name: " << strerror(errno) << std::endl;
 #endif
         }
 #endif