Example of how to use Conditional Compilation Macros in Rust

by

The correct way to test for a feature is feature = "name", as you can see in the documentation you linked if you scroll a bit:

As for how to enable or disable these switches, if you’re using Cargo,
they get set in the [features] section of your Cargo.toml:

[features]
# no features by default
default = []

# Add feature "foo" here, then you can use it. 
# Our "foo" feature depends on nothing else.
foo = []

When you do this, Cargo passes along a flag to rustc:

--cfg feature="${feature_name}"

The sum of these cfg flags will determine which ones get activated,
and therefore, which code gets compiled. Let’s take this code:

#[cfg(feature = "foo")]
mod foo {
}

In your case using the cfg! macro, this would map to cfg!(feature = "foo").

More Related Contents:

  1. Why can’t I store a value and a reference to that value in the same struct?
  2. The compiler suggests I add a ‘static lifetime because the parameter type may not live long enough, but I don’t think that’s what I want
  3. Is it possible to control the size of an array using the type parameter of a generic?
  4. Does println! borrow or own the variable?
  5. How do I pass disjoint slices from a vector to different threads?
  6. When should I implement std::convert::From vs std::convert::Into?
  7. Why is it possible to implement Read on an immutable reference to File?
  8. Compare enums only by variant, not value
  9. How can I call a mutating method while holding a reference to self?
  10. How do you actually use dynamically sized types in Rust?
  11. “parameter `’a` is never used” error when ‘a is used in type parameter bound
  12. Borrowing references to attributes in a struct
  13. How to operate on 2 mutable slices of a Rust array?
  14. Mutating one field while iterating over another immutable field
  15. How can I use a module from outside the src folder in a binary project, such as for integration tests or benchmarks?
  16. How to match on data type in Rust?
  17. Why does Rust allow mutation through a reference field using an immutable binding?
  18. How can I modify self in a closure called from a member function?
  19. What is a crate attribute and where do I add it?
  20. Parameter type may not live long enough?
  21. How to model complex recursive data structures (graphs)?
  22. Why can’t I reuse a &mut reference after passing it to a function that accepts a generic type?
  23. How can I define an async method in a trait?
  24. How do I specify the linker path in Rust?
  25. How do I specify that a struct field must implement a trait?
  26. What does Rust’s unary || (parallel pipe) mean?
  27. How to create and write to memory mapped files?
  28. Downcast traits inside Rc for AST manipulation
  29. How to check in Rust if architecture is 32 or 64 bit?
  30. Is there any way to restrict a generic type to one of several types?

Leave a Comment