diff -ur adplug-2.2.1-orig/src/s3m.cpp adplug-2.2.1/src/s3m.cpp

--- adplug-2.2.1-orig/src/s3m.cpp	2016-06-12 17:19:33.369934280 +0200

+++ adplug-2.2.1/src/s3m.cpp	2016-06-12 17:32:36.190932642 +0200

@@ -25,7 +25,7 @@

 #include <cstring>

 #include "s3m.h"

-const char Cs3mPlayer::chnresolv[] =	// S3M -> adlib channel conversion

+const signed char Cs3mPlayer::chnresolv[] =	// S3M -> adlib channel conversion

   {-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,0,1,2,3,4,5,6,7,8,-1,-1,-1,-1,-1,-1,-1};

 const unsigned short Cs3mPlayer::notetable[12] =		// S3M adlib note table

diff -ur adplug-2.2.1-orig/src/s3m.h adplug-2.2.1/src/s3m.h

--- adplug-2.2.1-orig/src/s3m.h	2016-06-12 17:19:33.367934293 +0200

+++ adplug-2.2.1/src/s3m.h	2016-06-12 17:37:14.538154102 +0200

@@ -90,7 +90,7 @@

   unsigned char crow,ord,speed,tempo,del,songend,loopstart,loopcnt;

  private:

-  static const char chnresolv[];

+  static const signed char chnresolv[];

   static const unsigned short notetable[12];

   static const unsigned char vibratotab[32];