Checkmint is a lightweight header-only library for C++20 that provides a proof-of-concept for checked variables, allowing you to enforce constraints that can help ensure data integrity in your code. It offers a convenient way to incorporate compile and runtime checks and enhance design-by-contract programming.
- Define checked variables with specified constraints using a simple syntax.
- Reinforce data integrity through automatic validation.
- Supports seamless composition and conversion of checked variables.
- Lightweight and header-only, making it easy to integrate into your projects.
Validators are stateless and need to be defined following a specific convention.
All examples assume
#include <checkmint/checkmint.hpp>
namespace cm = checkmint;Multiple validators are supported
struct Positive {
constexpr void operator()(int v)
{ CHECKMINT_SIGNAL_VIOLATION_IF_FALSE(v > 0, "Value smaller than zero"); }
};
struct NonZero {
constexpr void operator()(int v) {
CHECKMINT_SIGNAL_VIOLATION_IF_FALSE(v != 0, "Value is zero"); }
};
template <typename T>
using Denominator = cm::CheckedVar<T, NonZero>;
int divide(int numerator, Denominator<int> d)
{
return numerator / d.value();
}
int main() {
cm::CheckedVar<int, NonZero, Positive> valid_1(5); // OK
cm::CheckedVar<int, NonZero, Positive> valid_1(0); // Run-time error
constexpr cm::CheckedVar<int, NonZero, Positive> valid_1(-1); // Compile-time error
}A more complex example
#include <tuple>
#include <checkmint/checkmint.hpp>
template <typename... Ts>
struct ElementsAscending {
constexpr void operator()(const std::tuple<Ts...>& tuple) {
static_assert(sizeof...(Ts) >= 2, "Ordered tuple must have at least two elements");
check_elements<0, sizeof...(Ts)>(tuple);
}
private:
template <size_t Index, size_t Total>
constexpr void check_elements(const std::tuple<Ts...>& tuple) {
if constexpr (Index + 1 < Total) {
const auto& current = std::get<Index>(tuple);
const auto& next = std::get<Index + 1>(tuple);
CHECKMINT_SIGNAL_VIOLATION_IF_FALSE(current <= next, "Tuple elements are not in ascending order");
check_elements<Index + 1, Total>(tuple);
}
}
};
template <typename... Ts>
using CheckedOrderedTuple = cm::CheckedVar<std::tuple<Ts...>, ElementsAscending<Ts...>>;
int main()
{
constexpr CheckedOrderedTuple<int, int, int> orderedTuple({1, 4, 3}); // Compile time error
CheckedOrderedTuple<int, int, int> orderedTuple({1, 4, 3}); // Run-time error
CheckedOrderedTuple<int, int, int> valid_orderedTuple({1, 3, 4}); // OKAY
return 0;
}In the aforementioned example you get a simple compile-error message (GCC)
<source>: In function 'int main()':
<source>:346:72: in 'constexpr' expansion of 'checkmint::CheckedVar<std::tuple<int, int, int>, ElementsAscending<int, int, int> >(std::tuple<int, int, int>(1, 4, 3))'
<source>:88:32: in 'constexpr' expansion of 'checkmint::check_invariants<ElementsAscending<int, int, int>, std::tuple<int, int, int> >(((checkmint::CheckedVar<std::tuple<int, int, int>, ElementsAscending<int, int, int> >*)this)->checkmint::CheckedVar<std::tuple<int, int, int>, ElementsAscending<int, int, int> >::m_val)'
<source>:231:10: in 'constexpr' expansion of 'ElementsAscending<int, int, int>().ElementsAscending<int, int, int>::operator()((* & v))'
<source>:325:41: in 'constexpr' expansion of '((ElementsAscending<int, int, int>*)this)->ElementsAscending<int, int, int>::check_elements<0, 3>((* & tuple))'
<source>:335:45: in 'constexpr' expansion of '((ElementsAscending<int, int, int>*)this)->ElementsAscending<int, int, int>::check_elements<1, 3>((* & tuple))'
<source>:13:101: error: call to non-'constexpr' function 'int checkmint::invariant_violation(const std::string&)'
13 | #define CHECKMINT_SIGNAL_VIOLATION_IF_FALSE(cond, msg) if (!(cond)) checkmint::invariant_violation(msg)Tested on CLANG 16 and GCC 13.1