diff --git a/src/doc/book/no-stdlib.md b/src/doc/book/no-stdlib.md index 9823a0b6d6355..c5c139e6580b0 100644 --- a/src/doc/book/no-stdlib.md +++ b/src/doc/book/no-stdlib.md @@ -12,9 +12,26 @@ don’t want to use the standard library via an attribute: `#![no_std]`. > `#![no_std]`](using-rust-without-the-standard-library.html) Obviously there's more to life than just libraries: one can use -`#[no_std]` with an executable, controlling the entry point is -possible in two ways: the `#[start]` attribute, or overriding the -default shim for the C `main` function with your own. +`#[no_std]` with an executable. + +### Using libc + +In order to build a `#[no_std]` executable we will need libc as a dependency. We can specify +this using our `Cargo.toml` file: + +```toml +[dependencies] +libc = { version = "0.2.11", default-features = false } +``` + +Note that the default features have been disabled. This is a critical step - +**the default features of libc include the standard library and so must be +disabled.** + +### Writing an executable without stdlib + +Controlling the entry point is possible in two ways: the `#[start]` attribute, +or overriding the default shim for the C `main` function with your own. The function marked `#[start]` is passed the command line parameters in the same format as C: @@ -72,7 +89,6 @@ pub extern fn main(argc: i32, argv: *const *const u8) -> i32 { # // fn main() {} tricked you, rustdoc! ``` - The compiler currently makes a few assumptions about symbols which are available in the executable to call. Normally these functions are provided by the standard library, but without it you must define your own.