diff --git a/Makefile b/Makefile
index 805302d..fef99e2 100644
--- a/Makefile
+++ b/Makefile
@@ -5,13 +5,13 @@ SHARED_LIB = libsparsemap.so
 
 #CFLAGS = -Wall -Wextra -Wpedantic -Of -std=c11 -Iinclude/ -fPIC
 #CFLAGS = -Wall -Wextra -Wpedantic -Og -g -std=c11 -Iinclude/ -fPIC
-#CFLAGS = -DSPARSEMAP_DIAGNOSTIC -DDEBUG -Wall -Wextra -Wpedantic -O0 -g -std=c11 -Iinclude/ -fPIC
-CFLAGS = -Wall -Wextra -Wpedantic -Ofast -g -std=c11 -Iinclude/ -fPIC
+CFLAGS = -DSPARSEMAP_DIAGNOSTIC -DDEBUG -Wall -Wextra -Wpedantic -O0 -g -std=c11 -Iinclude/ -fPIC
+#CFLAGS = -Wall -Wextra -Wpedantic -Ofast -g -std=c11 -Iinclude/ -fPIC
 #CFLAGS = -DSPARSEMAP_DIAGNOSTIC -DDEBUG -Wall -Wextra -Wpedantic -Og -g -fsanitize=address,leak,object-size,pointer-compare,pointer-subtract,null,return,bounds,pointer-overflow,undefined -fsanitize-address-use-after-scope -std=c11 -Iinclude/ -fPIC
 #CFLAGS = -Wall -Wextra -Wpedantic -Og -g -fsanitize=all -fhardened -std=c11 -Iinclude/ -fPIC
 
-#TEST_FLAGS = -DDEBUG -Wall -Wextra -Wpedantic -O0 -g -std=c11 -Iinclude/ -Itests/ -fPIC
-TEST_FLAGS = -Wall -Wextra -Wpedantic -Ofast -g -std=c11 -Iinclude/ -Itests/ -fPIC
+TEST_FLAGS = -DDEBUG -Wall -Wextra -Wpedantic -O0 -g -std=c11 -Iinclude/ -Itests/ -fPIC
+#TEST_FLAGS = -Wall -Wextra -Wpedantic -Ofast -g -std=c11 -Iinclude/ -Itests/ -fPIC
 #TEST_FLAGS = -DDEBUG -Wall -Wextra -Wpedantic -Og -g -fsanitize=address,leak,object-size,pointer-compare,pointer-subtract,null,return,bounds,pointer-overflow,undefined -fsanitize-address-use-after-scope -std=c11 -Iinclude/ -fPIC
 
 TESTS = tests/test
diff --git a/include/sparsemap.h b/include/sparsemap.h
index 4c8dc7c..67b9364 100644
--- a/include/sparsemap.h
+++ b/include/sparsemap.h
@@ -260,11 +260,22 @@ size_t sparsemap_get_size(sparsemap_t *map);
  */
 void sparsemap_scan(sparsemap_t *map, void (*scanner)(sm_idx_t vec[], size_t n), size_t skip);
 
-/** @brief Splits the bitmap by assigning all bits starting at \b offset to the
+/** @brief Merges the values from \b other into the \b map, \b other is unchanged.
  * \b other bitmap while removing them from \b map.
  *
  * @param[in] map The sparsemap reference.
- * @param[in] skip Start the scan after "skip" bits.
+* @param[in] other The bitmap to merge into \b map.
+ */
+void sparsemap_merge(sparsemap_t *map, sparsemap_t *other);
+
+/** @brief Splits the bitmap by assigning all bits starting at \b offset to the
+ * \b other bitmap while removing them from \b map.
+ *
+ * The split must occur on a vector boundary.
+ *
+ * @param[in] map The sparsemap reference.
+ * @param[in] offset The 0-based offset into the bitmap at which to split.
+ * @param[in] other The bitmap into which we place the split.
  */
 void sparsemap_split(sparsemap_t *map, sparsemap_idx_t offset, sparsemap_t *other);
 
diff --git a/src/sparsemap.c b/src/sparsemap.c
index 7d22706..b68549a 100644
--- a/src/sparsemap.c
+++ b/src/sparsemap.c
@@ -1158,6 +1158,35 @@ sparsemap_scan(sparsemap_t *map, void (*scanner)(sm_idx_t[], size_t), size_t ski
   }
 }
 
+void
+sparsemap_merge(sparsemap_t *map, sparsemap_t *other)
+{
+  uint8_t *next_dst, *dst = __sm_get_chunk_map_data(map, 0);
+
+  /* |src| points to the |other| (source) chunk map */
+  uint8_t *next_src, *src = __sm_get_chunk_map_data(other, 0);
+
+  size_t i, src_count = __sm_get_chunk_map_count(other), dst_count = __sm_get_chunk_map_count(map);
+  for (i = 0; i < dst_count; i++) {
+    sm_idx_t src_start = *(sm_idx_t *)src;
+    sm_idx_t dst_start = *(sm_idx_t *)dst;
+    __sm_chunk_t src_chunk, dst_chunk;
+    __sm_chunk_map_init(&src_chunk, src + sizeof(sm_idx_t));
+    __sm_chunk_map_init(&dst_chunk, dst + sizeof(sm_idx_t));
+    if (src_start == dst_start) {
+      __sm_chunk_map_merge(dst, src);
+    } else {
+      next_dst = dst + sizeof(sm_idx_t) + __sm_chunk_map_get_size(&dst_chunk);
+      next_src = dst + sizeof(sm_idx_t) + __sm_chunk_map_get_size(&src_chunk);
+      if (src_start != next_dst) {
+        // Copy the chunk.
+      } else {
+        
+      }
+    }
+  }
+}
+
 void
 sparsemap_split(sparsemap_t *map, sparsemap_idx_t offset, sparsemap_t *other)
 {