1 unstable release
0.1.0 | Feb 6, 2024 |
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#453 in Memory management
10KB
104 lines
boxify
This crate provides a macro to initialize your Box<T>
on the heap without having to have it on the stack before.
This allows easily putting big arrays or structs containing them into a Box
without overflowing the stack:
// this would overflow the stack:
// let e = Box::new(Example {
// huge_array: [42; 1024 * 1024 * 1024],
// });
// this does not:
let e = boxify::boxify!(Example {
huge_array: [42; 1024 * 1024 * 1024],
});
Supported structures
Currently, this supports tuples, arrays and structs, even deeply nested ones. Take a look at the examples
folder to
see what's possible.
All other types are constructed on the stack and put into the box later.
Known Limitations
- Enums are not supported and can never be fully supported since their layout in memory is not fully specified.
- Only calls of lowercase function names and uppercase tuple struct instantiations are fully supported.
This limitation is necessary because there is no way to determine whether something is a function call or a tuple struct instantiation and both have to be handled differently, so this crate just uses the naming as a heuristic. The macro will cause a compiler error if it encounters a function where a struct was expected to prevent unsoundness. A lowercase tuple struct instantiation will quietly allocate on the stack and move it to the heap. - Struct update syntax, aka
Test { ..test }
is not allowed and causes a compiler error. This is because the macro needs to know all of the struct fields to fill them.
Dependencies
~0.5–1MB
~22K SLoC