Using static_assert with Non-constexpr Expressions

No, static_assert() cannot be used with expressions that are not evaluatable at compile-time. The expression passed to static_assert() must be a constant expression, meaning it can be evaluated by the compiler during compilation.

For example, this is not allowed:

1#include <cassert>
2
3int main() {
4  int x;
5  std::cin >> x;
6  static_assert(x > 0, "x must be positive");
7}

1error: static_assert expression is not an integral constant expression

For runtime assertions based on user input or values read from files, use regular assert() or a custom runtime assertion macro instead:

1#include <cassert>
2#include <iostream>
3
4int main() {
5  int x;
6  std::cin >> x;
7  assert(x > 0 && "x must be positive");
8}

Remember, assert() is typically stripped out in release builds, so you'd need to use a custom always-on assertion for checks you want enabled in release builds.

Some other notes on static_assert:

• The expression must be a boolean constant expression, not just any constant expression
• static_assert is evaluated at compile-time, so it cannot depend on any runtime information
• static_assert does not generate any runtime code or affect program performance
• Use static_assert to validate template parameters, sizes of types, and other invariants that can be checked at compile time