Ensuring the portability of user-defined literals across different compilers is crucial for maintaining cross-platform compatibility in C++ projects. Here are some best practices to follow:
The C++ standard specifies that user-defined literals must start with an underscore (_
). Adhering to this rule ensures that your literals are compliant with the standard and are less likely to cause conflicts with future standard library literals.
When defining user-defined literals, use the standard types that the C++ standard supports for literals:
unsigned long long
for integer literalslong double
for floating-point literalsconst char*
for string literalschar
for character literalsHere’s an example of portable user-defined literals:
#include <iostream>
class Distance {
public:
Distance(float value) : value{value} {}
float value;
};
std::ostream& operator<<(std::ostream& os, Distance d) {
os << d.value << " meters";
return os;
}
Distance operator""_meters(long double val) {
return Distance{static_cast<float>(val)};
}
Distance operator""_kilometers(long double val) {
return Distance{static_cast<float>(val * 1000)};
}
int main() {
Distance d = 1.5_kilometers;
std::cout << d;
}
1500 meters
Some compilers might allow non-standard features or extensions. Avoid using these extensions to maintain portability. Stick to the features defined in the C++Â standard.
Regularly test your code on multiple compilers, such as GCC, Clang, and MSVC. This practice helps identify and resolve any portability issues early in the development process.
Wrap your user-defined literals in namespaces to prevent naming conflicts. This practice helps ensure that your literals do not clash with literals from other libraries or future standard library additions.
#include <iostream>
class Distance {/*...*/};
namespace distance_literals {
Distance operator""_meters(long double val) {
return Distance{static_cast<float>(val)};
}
}
int main() {
using namespace distance_literals;
Distance d = 2.0_meters;
std::cout << d;
}
2 meters
By following these practices, you can ensure that your user-defined literals remain portable and maintainable across different compilers and platforms.
Answers to questions are automatically generated and may not have been reviewed.
A practical guide to user-defined literals in C++, which allow us to write more descriptive and expressive values