diff -ur a/mplex/main.cpp b/mplex/main.cpp
--- a/mplex/main.cpp	2021-09-05 02:14:13.029372000 -0400
+++ b/mplex/main.cpp	2023-09-23 08:47:07.683450627 -0400
@@ -50,7 +50,7 @@
 #include "multiplexor.hpp"
 
 
-using std::auto_ptr;
+using std::unique_ptr;
 
 
 /*************************************************************************
@@ -138,7 +138,7 @@
 void 
 FileOutputStream::NextSegment( )
 {
-    auto_ptr<char> prev_filename_buf( new char[strlen(cur_filename)+1] );
+    unique_ptr<char> prev_filename_buf( new char[strlen(cur_filename)+1] );
     char *prev_filename = prev_filename_buf.get();
 	fclose(strm);
 	++segment_num;
diff -ur a/utils/fastintfns.h b/utils/fastintfns.h
--- a/utils/fastintfns.h	2021-09-05 02:14:13.033372000 -0400
+++ b/utils/fastintfns.h	2023-09-23 08:44:40.147112973 -0400
@@ -2,12 +2,17 @@
  *
  * WARNING: Assumes 2's complement arithmetic.
  */
-static inline int intmax( register int x, register int y )
+#ifdef __cplusplus
+#define REGISTER
+#else
+#define REGISTER register
+#endif
+static inline int intmax( REGISTER int x, REGISTER int y )
 {
 	return x < y ? y : x;
 }
 
-static inline int intmin( register int x, register int y )
+static inline int intmin( REGISTER int x, REGISTER int y )
 {
 	return x < y ? x : y;
 }