playdate-allocator 0.1.0

Global allocator and allocator-api implementation for Playdate
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182

#![no_std]
#![cfg_attr(feature = "allocator-api", feature(allocator_api, slice_ptr_get))]
#![cfg_attr(feature = "global-error-handler",
            feature(alloc_error_handler, core_intrinsics),
            allow(internal_features))]
#![cfg_attr(any(test, debug_assertions, not(feature = "static-link")),
            feature(fn_ptr_trait))]


extern crate alloc;


#[cfg(feature = "allocator-api")]
pub(crate) mod local;
pub(crate) mod global;


/// PlaydateOs system allocator.
///
/// Allocator uses system `realloc` c-fn,
/// so user have to call [`init`] if `static-link` feature is disabled.
///
/// Otherwise if `static-link` is on, it's statically linked and it's nesessary to call [`init`].
pub struct System;


type Realloc = unsafe extern "C" fn(ptr: *mut c_void, size: usize) -> *mut c_void;


use core::ffi::c_void;

/// Fn-pointer to the OS's realloc function.
#[cfg(not(feature = "static-link"))]
static mut REALLOC: Realloc = fake;


/// Fake no-op realloc function, used as initial value (instead of any kinds of null) of [`REALLOC`].
/// Using this function will cause allocation failures.
#[cold]
#[cfg(not(feature = "static-link"))]
unsafe extern "C" fn fake(_: *mut c_void, _: usize) -> *mut c_void { core::ptr::null_mut() }


unsafe extern "C" {
	/// Statically linked OS's realloc function.
	#[cfg(feature = "static-link")]
	fn pdrealloc(ptr: *mut c_void, size: usize) -> *mut c_void;
}


#[inline(always)]
#[cfg(debug_assertions)]
pub fn init(realloc: Realloc) {
	use core::marker::FnPtr;

	debug_assert!(!realloc.addr().is_null());
	init_realloc(realloc)
}


#[inline(always)]
#[cfg(not(debug_assertions))]
pub const fn init(realloc: Realloc) { init_realloc(realloc) }


#[inline(always)]
#[cfg_attr(feature = "static-link",
           doc = "\n no-op because [`realloc`] is linked statically")]
const fn init_realloc(#[cfg_attr(feature = "static-link", allow(unused_variables))] realloc: Realloc) {
	#[cfg(not(feature = "static-link"))]
	unsafe {
		REALLOC = realloc
	}
}

#[inline(always)]
#[cfg(feature = "static-link")]
pub const fn is_inited() -> bool { true }


#[cfg(not(feature = "static-link"))]
pub fn is_inited() -> bool {
	use core::ptr::fn_addr_eq;
	unsafe { !fn_addr_eq(REALLOC, fake as Realloc) }
}


#[inline(always)]
#[cfg(debug_assertions)]
fn get() -> Realloc {
	let realloc = get_unchecked();

	#[cfg(not(feature = "static-link"))]
	debug_assert!(!core::marker::FnPtr::addr(realloc).is_null(), "missed realloc");

	realloc
}

#[inline(always)]
#[cfg(not(debug_assertions))]
const fn get() -> Realloc { get_unchecked() }


#[inline(always)]
const fn get_unchecked() -> Realloc {
	#[cfg(feature = "static-link")]
	{
		pdrealloc
	}
	#[cfg(not(feature = "static-link"))]
	{
		unsafe { REALLOC }
	}
}


#[cfg(test)]
#[cfg(not(feature = "global"))]
mod tests {
	#![allow(unexpected_cfgs)] // for `fake_alloc`.
	// It could be properly registered by adding to build-script `println!("cargo::rustc-check-cfg=cfg(fake_alloc)")`,
	// but it's only needed for tests and should not used in production,
	// so could be great if compiler warn about it in places other than tests.

	use core::ptr::null_mut;
	use super::*;


	#[test]
	#[cfg_attr(feature = "static-link", ignore = "for static-mut only")]
	fn not_inited() {
		#[cfg(not(feature = "static-link"))]
		unsafe {
			REALLOC = fake
		}
		assert!(!is_inited());
	}

	#[test]
	fn inited() {
		#[cfg(not(feature = "static-link"))]
		{
			unsafe { REALLOC = fake }
			assert!(!is_inited());
		}

		init_fake();

		assert!(is_inited());

		#[cfg(feature = "static-link")]
		assert!(!core::marker::FnPtr::addr(pdrealloc as Realloc).is_null());
	}


	#[test]
	#[cfg_attr(not(fake_alloc), ignore = "set RUSTFLAGS='--cfg=fake_alloc' to enable.")]
	fn get_alloc_fake() {
		init_fake();

		let realloc = get();
		let p = unsafe { realloc(null_mut(), 64) };

		assert!(p.is_null());
	}


	pub(crate) fn init_fake() {
		#[cfg(not(feature = "static-link"))]
		{
			// another fake, mem-location is different from crate::fake
			unsafe extern "C" fn fake(_: *mut c_void, _: usize) -> *mut c_void { null_mut() }
			unsafe { REALLOC = fake }
		}
	}


	#[no_mangle]
	#[cfg(fake_alloc)]
	#[cfg(feature = "static-link")]
	extern "C" fn pdrealloc(_: *mut c_void, _: usize) -> *mut c_void { null_mut() }
}