--- cinepaint-0.21-2-orig/plug-ins/bracketing_to_hdr/br_core/ResponseSolver.hpp 
+++ cinepaint-0.21-2/plug-ins/bracketing_to_hdr/br_core/ResponseSolver.hpp 
@@ -65,6 +65,7 @@
 
 
 #include <fstream>
+#include <cstring>              // strlen()
 #include "TNT/tnt_misc.hpp"     // proof_least_square_fit()
 #include "TNT/tnt_stopwatch.hpp"
 #include "TNT/jama_qr.hpp"      // JAMA::QR