[C] Return an actual ref count value after increment/decrement operat…

…ion completes + rename `aeron_image_refcnt_volatile` to `aeron_image_refcnt_acquire`.

aeron-client/src/main/c/aeron_client_conductor.c

@@ -526,7 +526,7 @@ int aeron_client_conductor_check_lingering_resources(aeron_client_conductor_t *c
                 }
             }
 
-            if (aeron_image_refcnt_volatile(image) <= 0)
+            if (aeron_image_refcnt_acquire(image) <= 0)
             {
                 aeron_client_conductor_release_log_buffer(conductor, image->log_buffer);
                 aeron_image_delete(image);
@@ -806,10 +806,7 @@ int aeron_client_conductor_linger_or_delete_all_images(
     for (size_t i = 0; i < current_image_list->length; i++)
     {
         aeron_image_t *image = current_image_list->array[i];
-        int64_t refcnt;
-
-        aeron_image_decr_refcnt(image);
-        refcnt = aeron_image_refcnt_volatile(image);
+        int64_t refcnt = aeron_image_decr_refcnt(image);
 
         aeron_array_to_ptr_hash_map_remove(
             &conductor->image_by_key_map,

aeron-client/src/main/c/aeron_image.c

@@ -845,4 +845,4 @@ extern int64_t aeron_image_incr_refcnt(aeron_image_t *image);
 
 extern int64_t aeron_image_decr_refcnt(aeron_image_t *image);
 
-extern int64_t aeron_image_refcnt_volatile(aeron_image_t *image);
+extern int64_t aeron_image_refcnt_acquire(aeron_image_t *image);

aeron-client/src/main/c/aeron_image.h

@@ -126,17 +126,17 @@ inline int64_t aeron_image_incr_refcnt(aeron_image_t *image)
 {
     int64_t result;
     AERON_GET_AND_ADD_INT64(result, image->refcnt, INT64_C(1));
-    return result;
+    return result + 1;
 }
 
 inline int64_t aeron_image_decr_refcnt(aeron_image_t *image)
 {
     int64_t result;
     AERON_GET_AND_ADD_INT64(result, image->refcnt, INT64_C(-1));
-    return result;
+    return result - 1;
 }
 
-inline int64_t aeron_image_refcnt_volatile(aeron_image_t *image)
+inline int64_t aeron_image_refcnt_acquire(aeron_image_t *image)
 {
     int64_t value;
     AERON_GET_ACQUIRE(value, image->refcnt);

aeron-client/src/test/c/aeron_image_test.cpp

@@ -1077,11 +1077,11 @@ TEST_F(ImageTest, shouldCorrectlyCountReferences)
 {
     createImage();
 
-    EXPECT_EQ(1, aeron_image_refcnt_volatile(m_image));
-    EXPECT_EQ(1, aeron_image_incr_refcnt(m_image));
-    EXPECT_EQ(2, aeron_image_refcnt_volatile(m_image));
-    EXPECT_EQ(2, aeron_image_decr_refcnt(m_image));
-    EXPECT_EQ(1, aeron_image_refcnt_volatile(m_image));
+    EXPECT_EQ(1, aeron_image_refcnt_acquire(m_image));
+    EXPECT_EQ(2, aeron_image_incr_refcnt(m_image));
+    EXPECT_EQ(2, aeron_image_refcnt_acquire(m_image));
     EXPECT_EQ(1, aeron_image_decr_refcnt(m_image));
-    EXPECT_EQ(0, aeron_image_refcnt_volatile(m_image));
+    EXPECT_EQ(1, aeron_image_refcnt_acquire(m_image));
+    EXPECT_EQ(0, aeron_image_decr_refcnt(m_image));
+    EXPECT_EQ(0, aeron_image_refcnt_acquire(m_image));
 }

aeron-client/src/test/cpp_wrapper/SystemTest.cpp

@@ -331,11 +331,10 @@ TEST_P(SystemTestParameterized, shouldFreeUnavailableImage)
 
         raw_image =
             aeron_subscription_image_by_session_id(raw_subscription, publication->sessionId());
-        EXPECT_EQ(4, aeron_image_decr_refcnt(raw_image));
-        EXPECT_EQ(3, aeron_image_refcnt_volatile(raw_image));
+        EXPECT_EQ(3, aeron_image_decr_refcnt(raw_image));
     }
 
-    EXPECT_EQ(1, aeron_image_refcnt_volatile(raw_image));
+    EXPECT_EQ(1, aeron_image_refcnt_acquire(raw_image));
     EXPECT_EQ(1, subscription->imageCount());
     EXPECT_EQ(1, aeron_subscription_image_count(raw_subscription));