compiler/rustc_target/src/spec/crt_objects.rs

   1 //! Object files providing support for basic runtime facilities and added to the produced binaries
   2 //! at the start and at the end of linking.
   3 //!
   4 //! Table of CRT objects for popular toolchains.
   5 //! The `crtx` ones are generally distributed with libc and the `begin/end` ones with gcc.
   6 //! See <https://dev.gentoo.org/~vapier/crt.txt> for some more details.
   7 //!
   8 //! | Pre-link CRT objects | glibc                  | musl                   | bionic           | mingw             | wasi         |
   9 //! |----------------------|------------------------|------------------------|------------------|-------------------|--------------|
  10 //! | dynamic-nopic-exe    | crt1, crti, crtbegin   | crt1, crti, crtbegin   | crtbegin_dynamic | crt2, crtbegin    | crt1         |
  11 //! | dynamic-pic-exe      | Scrt1, crti, crtbeginS | Scrt1, crti, crtbeginS | crtbegin_dynamic | crt2, crtbegin    | crt1         |
  12 //! | static-nopic-exe     | crt1, crti, crtbeginT  | crt1, crti, crtbegin   | crtbegin_static  | crt2, crtbegin    | crt1         |
  13 //! | static-pic-exe       | rcrt1, crti, crtbeginS | rcrt1, crti, crtbeginS | crtbegin_dynamic | crt2, crtbegin    | crt1         |
  14 //! | dynamic-dylib        | crti, crtbeginS        | crti, crtbeginS        | crtbegin_so      | dllcrt2, crtbegin | -            |
  15 //! | static-dylib (gcc)   | crti, crtbeginT        | crti, crtbeginS        | crtbegin_so      | dllcrt2, crtbegin | -            |
  16 //! | static-dylib (clang) | crti, crtbeginT        | N/A                    | crtbegin_static  | dllcrt2, crtbegin | -            |
  17 //! | wasi-reactor-exe     | N/A                    | N/A                    | N/A              | N/A               | crt1-reactor |
  18 //!
  19 //! | Post-link CRT objects | glibc         | musl          | bionic         | mingw  | wasi |
  20 //! |-----------------------|---------------|---------------|----------------|--------|------|
  21 //! | dynamic-nopic-exe     | crtend, crtn  | crtend, crtn  | crtend_android | crtend | -    |
  22 //! | dynamic-pic-exe       | crtendS, crtn | crtendS, crtn | crtend_android | crtend | -    |
  23 //! | static-nopic-exe      | crtend, crtn  | crtend, crtn  | crtend_android | crtend | -    |
  24 //! | static-pic-exe        | crtendS, crtn | crtendS, crtn | crtend_android | crtend | -    |
  25 //! | dynamic-dylib         | crtendS, crtn | crtendS, crtn | crtend_so      | crtend | -    |
  26 //! | static-dylib (gcc)    | crtend, crtn  | crtendS, crtn | crtend_so      | crtend | -    |
  27 //! | static-dylib (clang)  | crtendS, crtn | N/A           | crtend_so      | crtend | -    |
  28 //!
  29 //! Use cases for rustc linking the CRT objects explicitly:
  30 //!     - rustc needs to add its own Rust-specific objects (mingw is the example)
  31 //!     - gcc wrapper cannot be used for some reason and linker like ld or lld is used directly.
  32 //!     - gcc wrapper pulls wrong CRT objects (e.g. from glibc when we are targeting musl).
  33 //!
  34 //! In general it is preferable to rely on the target's native toolchain to pull the objects.
  35 //! However, for some targets (musl, mingw) rustc historically provides a more self-contained
  36 //! installation not requiring users to install the native target's toolchain.
  37 //! In that case rustc distributes the objects as a part of the target's Rust toolchain
  38 //! and falls back to linking with them manually.
  39 //! Unlike native toolchains, rustc only currently adds the libc's objects during linking,
  40 //! but not gcc's. As a result rustc cannot link with C++ static libraries (#36710)
  41 //! when linking in self-contained mode.
  42
  43 use crate::json::{Json, ToJson};
  44 use crate::spec::LinkOutputKind;
  45 use std::borrow::Cow;
  46 use std::collections::BTreeMap;
  47 use std::str::FromStr;
  48
  49 pub type CrtObjects = BTreeMap<LinkOutputKind, Vec<Cow<'static, str>>>;
  50
  51 pub(super) fn new(obj_table: &[(LinkOutputKind, &[&'static str])]) -> CrtObjects {
  52     obj_table.iter().map(|(z, k)| (*z, k.iter().map(|b| (*b).into()).collect())).collect()
  53 }
  54
  55 pub(super) fn all(obj: &'static str) -> CrtObjects {
  56     new(&[
  57         (LinkOutputKind::DynamicNoPicExe, &[obj]),
  58         (LinkOutputKind::DynamicPicExe, &[obj]),
  59         (LinkOutputKind::StaticNoPicExe, &[obj]),
  60         (LinkOutputKind::StaticPicExe, &[obj]),
  61         (LinkOutputKind::DynamicDylib, &[obj]),
  62         (LinkOutputKind::StaticDylib, &[obj]),
  63     ])
  64 }
  65
  66 pub(super) fn pre_musl_fallback() -> CrtObjects {
  67     new(&[
  68         (LinkOutputKind::DynamicNoPicExe, &["crt1.o", "crti.o", "crtbegin.o"]),
  69         (LinkOutputKind::DynamicPicExe, &["Scrt1.o", "crti.o", "crtbeginS.o"]),
  70         (LinkOutputKind::StaticNoPicExe, &["crt1.o", "crti.o", "crtbegin.o"]),
  71         (LinkOutputKind::StaticPicExe, &["rcrt1.o", "crti.o", "crtbeginS.o"]),
  72         (LinkOutputKind::DynamicDylib, &["crti.o", "crtbeginS.o"]),
  73         (LinkOutputKind::StaticDylib, &["crti.o", "crtbeginS.o"]),
  74     ])
  75 }
  76
  77 pub(super) fn post_musl_fallback() -> CrtObjects {
  78     new(&[
  79         (LinkOutputKind::DynamicNoPicExe, &["crtend.o", "crtn.o"]),
  80         (LinkOutputKind::DynamicPicExe, &["crtendS.o", "crtn.o"]),
  81         (LinkOutputKind::StaticNoPicExe, &["crtend.o", "crtn.o"]),
  82         (LinkOutputKind::StaticPicExe, &["crtendS.o", "crtn.o"]),
  83         (LinkOutputKind::DynamicDylib, &["crtendS.o", "crtn.o"]),
  84         (LinkOutputKind::StaticDylib, &["crtendS.o", "crtn.o"]),
  85     ])
  86 }
  87
  88 pub(super) fn pre_mingw_fallback() -> CrtObjects {
  89     new(&[
  90         (LinkOutputKind::DynamicNoPicExe, &["crt2.o", "rsbegin.o"]),
  91         (LinkOutputKind::DynamicPicExe, &["crt2.o", "rsbegin.o"]),
  92         (LinkOutputKind::StaticNoPicExe, &["crt2.o", "rsbegin.o"]),
  93         (LinkOutputKind::StaticPicExe, &["crt2.o", "rsbegin.o"]),
  94         (LinkOutputKind::DynamicDylib, &["dllcrt2.o", "rsbegin.o"]),
  95         (LinkOutputKind::StaticDylib, &["dllcrt2.o", "rsbegin.o"]),
  96     ])
  97 }
  98
  99 pub(super) fn post_mingw_fallback() -> CrtObjects {
 100     all("rsend.o")
 101 }
 102
 103 pub(super) fn pre_mingw() -> CrtObjects {
 104     all("rsbegin.o")
 105 }
 106
 107 pub(super) fn post_mingw() -> CrtObjects {
 108     all("rsend.o")
 109 }
 110
 111 pub(super) fn pre_wasi_fallback() -> CrtObjects {
 112     // Use crt1-command.o instead of crt1.o to enable support for new-style
 113     // commands. See https://reviews.llvm.org/D81689 for more info.
 114     new(&[
 115         (LinkOutputKind::DynamicNoPicExe, &["crt1-command.o"]),
 116         (LinkOutputKind::DynamicPicExe, &["crt1-command.o"]),
 117         (LinkOutputKind::StaticNoPicExe, &["crt1-command.o"]),
 118         (LinkOutputKind::StaticPicExe, &["crt1-command.o"]),
 119         (LinkOutputKind::WasiReactorExe, &["crt1-reactor.o"]),
 120     ])
 121 }
 122
 123 pub(super) fn post_wasi_fallback() -> CrtObjects {
 124     new(&[])
 125 }
 126
 127 /// Which logic to use to determine whether to fall back to the "self-contained" mode or not.
 128 #[derive(Clone, Copy, PartialEq, Hash, Debug)]
 129 pub enum CrtObjectsFallback {
 130     Musl,
 131     Mingw,
 132     Wasm,
 133 }
 134
 135 impl FromStr for CrtObjectsFallback {
 136     type Err = ();
 137
 138     fn from_str(s: &str) -> Result<CrtObjectsFallback, ()> {
 139         Ok(match s {
 140             "musl" => CrtObjectsFallback::Musl,
 141             "mingw" => CrtObjectsFallback::Mingw,
 142             "wasm" => CrtObjectsFallback::Wasm,
 143             _ => return Err(()),
 144         })
 145     }
 146 }
 147
 148 impl ToJson for CrtObjectsFallback {
 149     fn to_json(&self) -> Json {
 150         match *self {
 151             CrtObjectsFallback::Musl => "musl",
 152             CrtObjectsFallback::Mingw => "mingw",
 153             CrtObjectsFallback::Wasm => "wasm",
 154         }
 155         .to_json()
 156     }
 157 }