Should you use constexpr?
A constexpr integral value can be used wherever a const integer is required, such as in template arguments and array declarations. And when a value is computed at compile time instead of run time, it helps your program run faster and use less memory.
Should I use const or constexpr?
const applies for variables, and prevents them from being modified in your code. constexpr tells the compiler that this expression results in a compile time constant value, so it can be used in places like array lengths, assigning to const variables, etc.
Does C have constexpr?
Adding ‘constexpr’ support to C has no apparent downsides, it is just a preprocessor directive. However compiling C with C++, has a number of quirks that could break existing code. In addition, void* are used all the time in C (to get OOP-like behavior).
Is constexpr implicitly inline?
A function declared constexpr is implicitly an inline function. A deleted function is implicitly an inline function: its (deleted) definition can appear in more than one translation unit.
When to declare a function to be constexpr?
(with “every function” I always mean: every function that meets the requirements for being constexpr, i.e., is defined as a single return statement, takes only arguments of types with constexpr cstrs and calls only constexpr functions.
How can I tell if a constexpr function is being evaluated at run time?
In the Visual Studio debugger, when debugging a non-optimised Debug build, you can tell whether a constexpr function is being evaluated at compile time by putting a breakpoint inside it. If the breakpoint is hit, the function was called at run-time.
When does a constexpr function produce a compile time constant?
When its arguments are constexpr values, a constexpr function produces a compile-time constant. When called with non- constexpr arguments, or when its value isn’t required at compile time, it produces a value at run time like a regular function.
How does constexpr automatically apply to conforming functions?
It automatically applies constexpr to conforming functions and variables. Recently in our internal Slack channel, a co-worker was trying to create an exploitable binary where the vulnerability was an uninitialized stack local, but he was fighting the compiler.