diff --git a/src/xdiff/xhistogram.c b/src/xdiff/xhistogram.c
index 28cf825..8598a85 100644
--- a/src/xdiff/xhistogram.c
+++ b/src/xdiff/xhistogram.c
@@ -42,8 +42,6 @@
  */
 
 #include "xinclude.h"
-#include "xtypes.h"
-#include "xdiff.h"
 
 #define MAX_PTR	INT_MAX
 #define MAX_CNT	INT_MAX
@@ -55,8 +53,8 @@
 	struct record {
 		unsigned int ptr, cnt;
 		struct record *next;
-	} **records, // an occurrence
-	  **line_map; // map of line to record chain
+	} **records, /* an occurrence */
+	  **line_map; /* map of line to record chain */
 	chastore_t rcha;
 	unsigned int *next_ptrs;
 	unsigned int table_bits,
@@ -128,7 +126,7 @@
 				 */
 				NEXT_PTR(index, ptr) = rec->ptr;
 				rec->ptr = ptr;
-				// cap rec->cnt at MAX_CNT
+				/* cap rec->cnt at MAX_CNT */
 				rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
 				LINE_MAP(index, ptr) = rec;
 				goto continue_scan;
@@ -154,7 +152,7 @@
 		LINE_MAP(index, ptr) = rec;
 
 continue_scan:
-		; // no op
+		; /* no op */
 	}
 
 	return 0;
@@ -237,6 +235,8 @@
 		int line1, int count1, int line2, int count2)
 {
 	xpparam_t xpparam;
+
+	memset(&xpparam, 0, sizeof(xpparam));
 	xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
 
 	return xdl_fall_back_diff(env, &xpparam,
@@ -266,7 +266,7 @@
 
 	index.records = NULL;
 	index.line_map = NULL;
-	// in case of early xdl_cha_free()
+	/* in case of early xdl_cha_free() */
 	index.rcha.head = NULL;
 
 	index.table_bits = xdl_hashbits(count1);
@@ -288,7 +288,7 @@
 		goto cleanup;
 	memset(index.next_ptrs, 0, sz);
 
-	// lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx()
+	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
 	if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
 		goto cleanup;