Add bug triggering program in experiments.

It's a bug in pony, I only slightly modified counter.c such that
several threads send to one actor. The actor mailbox has a race that
leads to a crash. We'll need Sylvain's help to fix it without hurting
performance terribly.

experiments/Makefile

@@ -15,6 +15,9 @@ $(LIBPONY_A_PATH):
 	cd $(SRC_PATH); make clean_pony
 	make -C $(SRC_PATH); make
 
+counter: counter.c
+	  clang -ggdb -Wall -Werror ~/code/mylittlepony/release/lib/* -I ~/code/mylittlepony/release/inc counter.c -o counter
+
 Futures.test: Futures.test.c
 	clang -std=c11 -ggdb -Wall -I../src/runtime -I../src/runtime/set -I../src/runtime/future -I../src/runtime/pony/inc/ -I../src/runtime/pony/src Futures.test.c `find ../src/runtime/pony/obj/Debug/pony -name "*.o"` ../src/runtime/future/future.o ../src/runtime/future/future_actor.o ../src/runtime/set/set.o ../src/runtime/future/ccontext.o -o Futures.test
 

experiments/counter.c

@@ -0,0 +1,114 @@
+#include <pony/pony.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+typedef struct counter_t
+{
+  uint64_t count;
+} counter_t;
+
+enum
+{
+  MSG_INIT,
+  MSG_INC,
+  MSG_SHOOT_ME,
+  MSG_GETANDRESET,
+  MSG_RESPONSE
+};
+
+static pony_msg_t m_init = {0, {{NULL, 0, PONY_PRIMITIVE}}};
+static pony_msg_t m_inc = {0, {{NULL, 0, PONY_PRIMITIVE}}};
+static pony_msg_t m_shootme = {1, {{NULL, 0, PONY_ACTOR}}};
+static pony_msg_t m_getandreset = {1, {{NULL, 0, PONY_ACTOR}}};
+static pony_msg_t m_response = {1, {{NULL, 8, PONY_PRIMITIVE}}};
+
+static void trace(void* p)
+{
+  counter_t* d = p;
+  pony_trace64(&d->count);
+}
+
+static pony_msg_t* message_type(uint64_t id)
+{
+  switch(id)
+  {
+    case MSG_INIT: return &m_init;
+    case MSG_INC: return &m_inc;
+    case MSG_GETANDRESET: return &m_getandreset;
+    case MSG_RESPONSE: return &m_response;
+    case MSG_SHOOT_ME: return &m_shootme;
+  }
+
+  return NULL;
+}
+
+static void dispatch(pony_actor_t* this, void* p, uint64_t id, int argc, pony_arg_t* argv);
+
+static pony_actor_type_t type =
+{
+  1,
+  {trace, sizeof(counter_t), PONY_ACTOR},
+  message_type,
+  dispatch
+};
+
+static void dispatch(pony_actor_t* this, void* p, uint64_t id, int argc, pony_arg_t* argv)
+{
+  counter_t* d = p;
+
+  switch(id)
+  {
+  case PONY_MAIN:
+    {
+      printf("starting..\n");
+      //int margc = argv[0].i;
+      //char** margv = argv[1].p;
+      //uint64_t count = 0;
+
+      const int N = 20;
+      pony_actor_t *actors[N];
+      for (int i = 0; i<N; ++i) {
+        actors[i] = pony_create(&type);
+        pony_arg_t arg = {.p = this };
+        pony_sendp(actors[i], MSG_SHOOT_ME, &arg);
+
+        //pony_sendp(actor, MSG_GETANDRESET, this);
+      }
+
+      break;
+    }
+  case MSG_SHOOT_ME:
+    {
+      printf("shooting..\n");
+      pony_actor_t *me = argv[1].p;
+      for (int i=0; i < 1000; i++) {
+        pony_send(me, MSG_INC);
+      }
+      break;
+    }
+  case MSG_INIT:
+    d = pony_alloc(sizeof(counter_t));
+    d->count = 0;
+    pony_set(d);
+    break;
+
+  case MSG_INC:
+    d->count++;
+    printf("count = %llu\n",d->count);
+    break;
+
+  case MSG_GETANDRESET:
+    pony_sendi(argv[0].p, MSG_RESPONSE, d->count);
+    d->count = 0;
+    break;
+
+  case MSG_RESPONSE:
+    printf("%lu\n", argv[0].i);
+    break;
+  }
+}
+
+int main(int argc, char** argv)
+{
+  return pony_start(argc, argv, pony_create(&type));
+}