Cereal seems to not properly serialize an std::string - c++

Question

I am trying to serialize a class into a binary, to that effect I first started trying to serialize an std::string member within the class, I wrote this serialization method:
template<typename Archive>
void ShaderProgram::serialize(Archive& archive, ShaderProgram& program)
{
archive(CEREAL_NVP(program.program_name));
}
Then I am trying to serialize and immediately read the class:
ShaderProgram program;
std::filesystem::create_directories(fs::path(cached_shader_path).parent_path());
std::ofstream os(cached_shader_path, std::ios::binary);
cereal::BinaryOutputArchive archive_out( os );
ShaderProgram::serialize(archive_out, program);
std::ifstream is(cached_shader_path, std::ios::binary);
cereal::BinaryInputArchive archive_in( is );
ShaderProgram::serialize(archive_in, program);
Which results in:
terminate called after throwing an instance of 'cereal::Exception'
what(): Failed to read 8 bytes from input stream! Read 0
The class I am testing this with is trivial:
struct ShaderProgram
{
std::string program_name = "name";
template<typename Archive>
static void serialize(Archive& archive, ShaderProgram& program);
};
template<typename Archive>
void ShaderProgram::serialize(Archive& archive, ShaderProgram& program)
{
archive(CEREAL_NVP(program.program_name));
}
I don;t understand why this fails.

Answer 1

Here is an example. All is fine with cereal. In plain C++ remove Rcpp connections.
// [[Rcpp::depends(Rcereal)]]
#include <string>
#include <fstream>
#include <cereal/archives/binary.hpp>
#include <cereal/types/string.hpp>
#include <cereal/access.hpp>
#include <Rcpp.h>
struct ShaderProgram
{
ShaderProgram(){};
ShaderProgram(std::string program_name)
: program_name{program_name}{};
~ShaderProgram() = default;
std::string get_program_name() const {
return program_name;
}
private:
std::string program_name{};
friend class cereal::access;
template<class Archive>
void serialize(Archive& archive)
{
archive(program_name);
}
};
// [[Rcpp::export]]
int main() {
{
ShaderProgram sp("King Kong 8");
std::ofstream os("Backend/Serialize_StringProgram.bin", std::ios::binary);
cereal::BinaryOutputArchive oarchive(os);
oarchive(sp);
}
{
ShaderProgram sp{};
std::ifstream is("Backend/Serialize_StringProgram.bin", std::ios::binary);
cereal::BinaryInputArchive iarchive(is);
iarchive(sp);
Rcpp::Rcout << sp.get_program_name() << std::endl;
}
}