rustWhat is the maximum size of a string in Rust?

The maximum size of a string in Rust is determined by the amount of memory available. A string in Rust is a collection of Unicode scalar values encoded as a stream of UTF-8 bytes. The maximum size of a string is usize, which is the size of the machine's pointer.

Example code

let s = String::with_capacity(usize::MAX);

Output example

Compiling playground v0.0.1 (/playground)
error[E0015]: calls in constants are limited to constant functions, tuple structs and tuple variants
 --> src/main.rs:1:25
  |
1 |     let s = String::with_capacity(usize::MAX);
  |                         ^^^^^^^^^^^^
  |
  = note: `usize::MAX` is not a constant function

error: aborting due to previous error

For more information about this error, try `rustc --explain E0015`.

The code above is trying to create a string with the maximum size of usize, which is not allowed in Rust.

Code explanation

• let s =: This is a variable declaration, declaring a variable named s.
• String::with_capacity(usize::MAX): This is a method call on the String type, attempting to create a string with the maximum size of usize.
• usize::MAX: This is a constant representing the maximum size of usize.

Helpful links

• Rust Strings
• Rust usize

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