kc3-lang/ftgl

diff --git a/demo/tb.h b/demo/tb.h
index de0f00c..3ac0ea8 100644
--- a/demo/tb.h
+++ b/demo/tb.h
@@ -76,6 +76,10 @@
 
 
 /* functions */
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void
 tbInit(GLuint button);
 
@@ -93,3 +97,7 @@ tbMotion(int x, int y);
 
 void
 tbAnimate(GLboolean animate);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/demo/trackball.h b/demo/trackball.h
index b676fb4..3aea4ee 100644
--- a/demo/trackball.h
+++ b/demo/trackball.h
@@ -40,6 +40,10 @@
  * Written by Gavin Bell for Silicon Graphics, November 1988.
  */
 
+#ifdef __cpluscplus
+extern "C" {
+#endif
+
 /*
  * Pass the x and y coordinates of the last and current positions of
  * the mouse, scaled so they are from (-1.0 ... 1.0).
@@ -76,3 +80,6 @@ build_rotmatrix(float m[4][4], float q[4]);
 void
 axis_to_quat(float a[3], float phi, float q[4]);
 
+#ifdef __cpluscplus
+}
+#endif