How to make changes in a .tpp template implementation file trigger recompilation in a Makefile?

I'm using .tpp files to store template implementations.

However, modifying a .tpp file does not trigger recompilation, because Make does not generate an .o file from a .tpp source.

Still, these changes affect the compilation of .cpp files that include the corresponding .hpp.

How can I make Make recompile when a .tpp file is changed?

MRE.hpp

#pragma once #include <iostream> template <typename T> class MRE { T a; public: void write(std::ostream&); }; #include "MRE.tpp"

MRE.tpp

template <typename T> void MRE<T>::write(std::ostream& os) { os << "initial message"; }

TestMRE.cpp

#include "MRE.hpp" int main() { MRE<int> m; m.write(std::cout); std::cout << std::endl; }

Initial Makefile

TestMRE: TestMRE.o $(CXX) $(CXXFLAGS) $^ -o $@ %.o: %.cpp %.hpp $(CXX) $(CXXFLAGS) -c $< -o $@

Observed behavior

Running the program prints:

initial message

I change "initial message" to "final message" in MRE.tpp.

Running make prints:

make: 'TestMRE' is up to date.

Running the program again still prints:

initial message