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#![no_std] #![allow(clippy::missing_safety_doc)] //! Module initialization termination function with priorities and (mutable) statics initialization with //! non const functions. //! //! //! # Functionalities //! //! - Code execution before or after `main` but after libc and rust runtime has been initialized //! (but not alway std::env see doc bellow) //! - Mutable and const statics with non const initialization. //! - Statics dropable after `main` exits. //! - Zero cost access to statics. //! - Priorities on elf plateforms (linux, bsd, etc...) and window. //! //! # Example //! ```rust //! use static_init::{constructor,destructor,dynamic}; //! //! #[constructor] //! unsafe fn do_init(){ //! } //! //Care not to use priorities above 65535-100 //! //as those high priorities are used by //! //the rust runtime. //! #[constructor(200)] //! unsafe fn do_first(){ //! } //! //! #[destructor] //! unsafe fn finaly() { //! } //! #[destructor(100)] //! unsafe fn ultimately() { //! } //! //! #[dynamic] //! static V: Vec<i32> = unsafe {vec![1,2,3]}; //! //! #[dynamic(init,drop)] //! static mut V1: Vec<i32> = unsafe {vec![1,2,3]}; //! //! //Initialized before V1 //! //then destroyed after V1 //! #[dynamic(init=142,drop=142)] //! static mut INIT_AND_DROP: Vec<i32> = unsafe {vec![1,2,3]}; //! //! fn main(){ //! assert_eq!(V[0],1); //! unsafe{ //! assert_eq!(V1[2],3); //! V1[2] = 42; //! assert_eq!(V1[2], 42); //! } //! } //! ``` //! //! # Attributes //! //! All functions marked with the [constructor] attribute are //! run before `main` is started. //! //! All function marked with the [destructor] attribute are //! run after `main` has returned. //! //! Static variables marked with the [dynamic] attribute can //! be initialized before main start and optionaly droped //! after main returns. //! //! The attributes [constructor] and [destructor] works by placing the marked function pointer in //! dedicated object file sections. //! //! Priority ranges from 0 to 2<sup>16</sup>-1. The absence of priority is equivalent to //! a hypothetical priority number of -1. //! //! During program initialization: //! //! - constructors with priority 65535 are the first called; //! - constructors without priority are called last. //! //! During program termination, the order is reversed: //! //! - destructors without priority are the first called; //! - destructors with priority 65535 are the last called. //! //! # Safety //! //! Use of the *functionnalities provided by this library are inherently unsafe*. During //! execution of a constructor, any access to variable initialized with a lower or equal priority //! will cause undefined behavior. During execution of a destructor any access //! to variable droped with a lower or equal priority will cause undefined //! behavior. //! //! This is actually the reason to be of the priorities: this is the coder own responsability //! to ensure that no access is performed to lower or equal priorities. //! //! ```no_run //! use static_init::dynamic; //! //! #[dynamic] //! static V1: Vec<i32> = unsafe {vec![1,2,3]}; //! //! //potential undefined behavior: V1 may not have been initialized yet //! #[dynamic] //! static V2: i32 = unsafe {V1[0]}; //! //! //undefined behavior, V3 is unconditionnaly initialized before V1 //! #[dynamic(1000)] //! static V3: i32 = unsafe {V1[0]}; //! //! #[dynamic(1000)] //! static V4: Vec<i32> = unsafe {vec![1,2,3]}; //! //! //Good, V5 initialized after V4 //! #[dynamic(500)] //! static V5: i32 = unsafe {V4[0]}; //! //! //Good, V6 initialized after V5 and v4 //! #[dynamic] //! static V6: i32 = unsafe {*V5+V4[1]}; //! //! //! # fn main(){} //! ``` //! //! # Comparisons against other crates //! //! ## [lazy_static][1] //! - lazy_static only provides const statics. //! - Each access to lazy_static statics costs 2ns on a x86. //! - lazy_static does not provide priorities. //! - lazy_static statics initialization is *safe*. //! //! ## [ctor][2] //! - ctor only provides const statics. //! - ctor does not provide priorities. //! //! # Documentation and details //! //! ## Mac //! - [MACH_O specification](https://www.cnblogs.com/sunkang/archive/2011/05/24/2055635.html) //! - GCC source code gcc/config/darwin.c indicates that priorities are not supported. //! //! Initialization functions pointers are placed in section "__DATA,__mod_init_func" and //! "__DATA,__mod_term_func" //! //! std::env is not initialized in any constructor. //! //! ## ELF plateforms: //! - `info ld` //! - linker script: `ld --verbose` //! - [ELF specification](https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter7-1.html#scrolltoc) //! //! The runtime will run fonctions pointers of section ".init_array" at startup and function //! pointers in ".fini_array" at program exit. The linker place in the target object file //! sectio .init_array all sections from the source objects whose name is of the form //! .init_array.NNNNN in lexicographical order then the .init_array sections of those same source //! objects. It does equivalently with .fini_array and .fini_array.NNNN sections. //! //! Usage can be seen in gcc source gcc/config/pru.c //! //! Resources of libstdc++ are initialized with priority 65535-100 (see gcc source libstdc++-v3/c++17/default_resource.h) //! The rust standard library function that capture the environment and executable arguments is //! executed at priority 65535-99 on gnu platform variants. On other elf plateform they are not accessbile in any constructors. Nevertheless //! one can read into /proc/self directory to retrieve the command line. //! Some callbacks constructors and destructors with priority 65535 are //! registered by rust/rtlibrary. //! Static C++ objects are usually initialized with no priority (TBC). lib-c resources are //! initialized by the C-runtime before any function in the init_array (whatever the priority) are executed. //! //! ## Windows //! //! std::env is initialized before any constructors. //! //! - [this blog post](https://www.cnblogs.com/sunkang/archive/2011/05/24/2055635.html) //! //! At start up, any functions pointer between sections ".CRT$XIA" and ".CRT$XIZ" //! and then any functions between ".CRT$XCA" and ".CRT$XCZ". It happens that the C library //! initialization functions pointer are placed in ".CRT$XIU" and C++ statics functions initialization //! pointers are placed in ".CRT$XCU". At program finish the pointers between sections //! ".CRT$XPA" and ".CRT$XPZ" are run first then those between ".CRT$XTA" and ".CRT$XTZ". //! //! Some reverse engineering was necessary to find out a way to implement //! constructor/destructor priority. //! //! Contrarily to what is reported in this blog post, msvc linker //! only performs a lexicographicall ordering of section whose name //! is of the form "\<prefix\>$\<suffix\>" and have the same \<prefix\>. //! For example "RUST$01" and "RUST$02" will be ordered but those two //! sections will not be ordered with "RHUM" section. //! //! Moreover, it seems that section name of the form \<prefix\>$\<suffix\> are //! not limited to 8 characters. //! //! So static initialization function pointers are placed in section ".CRT$XCU" and //! those with a priority `p` in `format!(".CRT$XCTZ{:05}",65535-p)`. Destructors without priority //! are placed in ".CRT$XPU" and those with a priority in `format!(".CRT$XPTZ{:05}",65535-p)`. //! //! //! [1]: https://crates.io/crates/lazy_static //! [2]: https://crates.io/crates/ctor use core::cell::UnsafeCell; use core::mem::ManuallyDrop; use core::ops::{Deref, DerefMut}; #[doc(inline)] pub use static_init_macro::constructor; #[doc(inline)] pub use static_init_macro::destructor; #[doc(inline)] pub use static_init_macro::dynamic; /// The actual type of "dynamic" mutable statics. /// /// It implements `Deref<Target=T>` and `DerefMut`. /// /// All associated functions are only usefull for the implementation of /// the [dynamic] proc macro attribute pub union Static<T> { #[used] k: (), v: ManuallyDrop<T>, } //As a trait in order to avoid noise; impl<T> Static<T> { #[inline] pub const fn uninit() -> Self { Self { k: () } } #[inline] pub const fn from(v: T) -> Self { Static { v: ManuallyDrop::new(v), } } #[inline] pub unsafe fn set_to(this: &mut Self, v: T) { *this = Self::from(v); } #[inline] pub unsafe fn drop(this: &mut Self) { ManuallyDrop::drop(&mut this.v); } } impl<T> Deref for Static<T> { type Target = T; #[inline] fn deref(&self) -> &T { unsafe { &*self.v } } } impl<T> DerefMut for Static<T> { #[inline] fn deref_mut(&mut self) -> &mut T { unsafe { &mut *self.v } } } /// The actual type of "dynamic" non mutable statics. /// /// It implements `Deref<Target=T>`. /// /// All associated functions are only usefull for the implementation of /// the [dynamic] proc macro attribute pub struct ConstStatic<T>(UnsafeCell<Static<T>>); impl<T> ConstStatic<T> { #[inline] pub const fn uninit() -> Self { Self(UnsafeCell::new(Static::uninit())) } #[inline] pub const fn from(v: T) -> Self { Self(UnsafeCell::new(Static::from(v))) } #[inline] pub unsafe fn set_to(this: &Self, v: T) { *this.0.get() = Static::from(v) } #[inline] pub unsafe fn drop(this: &Self) { Static::drop(&mut *this.0.get()); } } unsafe impl<T: Send> Send for ConstStatic<T> {} unsafe impl<T: Sync> Sync for ConstStatic<T> {} impl<T> Deref for ConstStatic<T> { type Target = T; #[inline] fn deref(&self) -> &T { unsafe { &**self.0.get() } } }