Throw/assert method as customization point?

assert.hpp

#pragma once

#ifdef MY_LIB_THROW_INSTEAD_OF_ASSERT
#include <stdexcept>
#define MY_LIB_ASSERT(condition) \
  if (not condition) throw std::runtime_error(#condition)
#endif

#ifndef MY_LIB_ASSERT
#include <cassert>
#define MY_LIB_ASSERT(condition) (assert(condition))
#endif

foo.cpp

#include "foo.hpp"

#include "assert.hpp"

namespace my_lib {

foo::foo(int x)
: x_(x)
{
  MY_LIB_ASSERT(x != 0);
}

int
foo::get_x() const
{
  return this->x_;
}

}

foo.hpp

#pragma once

namespace my_lib {

class foo {
public:
  foo(int x);
  int get_x() const;
private:
  int x_;
};

}

main.cpp

#include "foo.hpp"

int main()
{
  my_lib::foo x(0);
  if (x.get_x() == 0) {
    return -1;
  }
  return 0;
}

Makefile

.PHONY: all

all: foo_with_assert foo_with_throw

foo_with_assert: assert.hpp foo.hpp foo.cpp main.cpp
  g++ -std=c++11 -o foo_with_assert main.cpp foo.cpp -g -O0

foo_with_throw: assert.hpp foo.hpp foo.cpp main.cpp
  g++ -std=c++11 -o foo_with_throw main.cpp foo.cpp -g -O0 -
DMY_LIB_THROW_INSTEAD_OF_ASSERT