diff --git a/Makefile b/Makefile
index 1728d2b1fc..205c9ae46c 100755
--- a/Makefile
+++ b/Makefile
@@ -77,6 +77,6 @@ ifeq ($(wildcard dependencies/install/include/gflags/gflags.h),)
 endif
 
 .PHONY: detect
-detect: detect_port detect_python detect_java detect_csharp detect_fsharp
+detect: detect_port detect_cc detect_python detect_java detect_csharp detect_fsharp
 
 print-%  : ; @echo $* = $($*)
diff --git a/makefiles/Makefile.cpp.mk b/makefiles/Makefile.cpp.mk
index e2f3b403cb..8945b16f4c 100755
--- a/makefiles/Makefile.cpp.mk
+++ b/makefiles/Makefile.cpp.mk
@@ -659,7 +659,16 @@ rcc: $(BIN_DIR)$S$(basename $(notdir $(EX)))$E
 	@echo running $(BIN_DIR)$S$(basename $(notdir $(EX)))$E
 	$(BIN_DIR)$S$(basename $(notdir $(EX)))$E $(ARGS)
 
+.PHONY: detect_cc # Show variables used to build C++ OR-Tools.
+detect_cc:
+	@echo CCC = $(CCC)
+	@echo CFLAGS = $(CFLAGS)
+	@echo OR_TOOLS_LIBS = $(OR_TOOLS_LIBS)
+	@echo OR_TOOLS_LNK = $(OR_TOOLS_LNK)
+	@echo OR_TOOLS_LD_FLAGS = $(OR_TOOLS_LD_FLAGS)
+
 # Debug
+.PHONY: printdir
 printdir:
 	@echo LIB_DIR = $(LIB_DIR)
 	@echo BIN_DIR = $(BIN_DIR)