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2b03887a FG |
1 | #![feature(unix_sigpipe)] |
2 | ||
a2a8927a XL |
3 | // A note about jemalloc: rustc uses jemalloc when built for CI and |
4 | // distribution. The obvious way to do this is with the `#[global_allocator]` | |
5 | // mechanism. However, for complicated reasons (see | |
6 | // https://github.com/rust-lang/rust/pull/81782#issuecomment-784438001 for some | |
7 | // details) that mechanism doesn't work here. Also, we must use a consistent | |
8 | // allocator across the rustc <-> llvm boundary, and `#[global_allocator]` | |
9 | // wouldn't provide that. | |
cdc7bbd5 | 10 | // |
a2a8927a XL |
11 | // Instead, we use a lower-level mechanism. rustc is linked with jemalloc in a |
12 | // way such that jemalloc's implementation of `malloc`, `free`, etc., override | |
13 | // the libc allocator's implementation. This means that Rust's `System` | |
14 | // allocator, which calls `libc::malloc()` et al., is actually calling into | |
15 | // jemalloc. | |
16 | // | |
17 | // A consequence of not using `GlobalAlloc` (and the `tikv-jemallocator` crate | |
18 | // provides an impl of that trait, which is called `Jemalloc`) is that we | |
19 | // cannot use the sized deallocation APIs (`sdallocx`) that jemalloc provides. | |
20 | // It's unclear how much performance is lost because of this. | |
21 | // | |
22 | // As for the symbol overrides in `main` below: we're pulling in a static copy | |
23 | // of jemalloc. We need to actually reference its symbols for it to get linked. | |
24 | // The two crates we link to here, `std` and `rustc_driver`, are both dynamic | |
25 | // libraries. So we must reference jemalloc symbols one way or another, because | |
26 | // this file is the only object code in the rustc executable. | |
cdc7bbd5 | 27 | |
2b03887a | 28 | #[unix_sigpipe = "sig_dfl"] |
83c7162d | 29 | fn main() { |
a2a8927a | 30 | // See the comment at the top of this file for an explanation of this. |
923072b8 | 31 | #[cfg(feature = "jemalloc-sys")] |
0731742a | 32 | { |
dfeec247 | 33 | use std::os::raw::{c_int, c_void}; |
0731742a XL |
34 | |
35 | #[used] | |
dfeec247 | 36 | static _F1: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::calloc; |
0731742a | 37 | #[used] |
dfeec247 | 38 | static _F2: unsafe extern "C" fn(*mut *mut c_void, usize, usize) -> c_int = |
0731742a XL |
39 | jemalloc_sys::posix_memalign; |
40 | #[used] | |
dfeec247 | 41 | static _F3: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::aligned_alloc; |
0731742a | 42 | #[used] |
dfeec247 | 43 | static _F4: unsafe extern "C" fn(usize) -> *mut c_void = jemalloc_sys::malloc; |
0731742a | 44 | #[used] |
dfeec247 | 45 | static _F5: unsafe extern "C" fn(*mut c_void, usize) -> *mut c_void = jemalloc_sys::realloc; |
0731742a | 46 | #[used] |
dfeec247 | 47 | static _F6: unsafe extern "C" fn(*mut c_void) = jemalloc_sys::free; |
6a06907d XL |
48 | |
49 | // On OSX, jemalloc doesn't directly override malloc/free, but instead | |
50 | // registers itself with the allocator's zone APIs in a ctor. However, | |
51 | // the linker doesn't seem to consider ctors as "used" when statically | |
52 | // linking, so we need to explicitly depend on the function. | |
53 | #[cfg(target_os = "macos")] | |
54 | { | |
55 | extern "C" { | |
56 | fn _rjem_je_zone_register(); | |
57 | } | |
58 | ||
59 | #[used] | |
60 | static _F7: unsafe extern "C" fn() = _rjem_je_zone_register; | |
61 | } | |
0731742a XL |
62 | } |
63 | ||
83c7162d XL |
64 | rustc_driver::main() |
65 | } |