Add more details to the rules

README.md

@@ -4,14 +4,46 @@
   <img src="./crust.png" width=200>
 </p>
 
-1. Every function is unsafe.
-1. No references, only pointers.
-1. No cargo, build with rustc directly.
-1. No std, but libc is allowed.
-1. Only Edition 2021.
-1. All user structs and enums #[derive(Clone, Copy)].
-1. Everything is pub by default.
-
 *The list of rules may change. The goal is to make programming in Rust fun.*
 
 Currently used in the [B Compiler Project](https://github.com/tsoding/b).
+
+## 1. No std.
+
+Use [`#![no_std]`][no_std] attribute to enforce this rule. [core][core] is allowed because there is currently [no stable way to disable it](https://github.com/rust-lang/rust/issues/29639). Using libc is allowed since rustc links with it anyway. But since no cargo is allowed you have to declare the necessary libc functions yourself in your crate.
+
+You may also consider enabling [`#![no_main]`][no_main] and provide your custom C-style entry point to be able to get an access to command line arguments.
+
+## 2. Every function is unsafe.
+
+Every single user-made function must be marked as unsafe.
+
+## 3. Raw pointers instead of references.
+
+Raw pointers instead of references must be used for:
+
+1. Parameters and results of all the user-made functions;
+2. Members of user-made structs and enums;
+3. User-made global variables;
+
+In the bodies of the functions references are allowed to be used for local variables and intermediate value.
+
+## 4. No cargo.
+
+Build with rustc directly pure C-style. Linking with external C libraries is encouraged.
+
+## 5. Only Edition 2021.
+
+Newer additions are too hostile towards Crust.
+
+## 6. Copy by default.
+
+All user-made structs and enums must be `#[derive(Clone, Copy)]`
+
+## 7. Public by default.
+
+Everything is `pub` by default.
+
+[core]: https://doc.rust-lang.org/stable/core/index.html
+[no_std]: https://doc.rust-lang.org/reference/names/preludes.html#the-no_std-attribute
+[no_main]: https://doc.rust-lang.org/reference/crates-and-source-files.html?highlight=no_main#the-no_main-attribute