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::spec::LinkOutputKind;
  44 use rustc_serialize::json::{Json, ToJson};
  45 use std::collections::BTreeMap;
  46 use std::str::FromStr;
  47
  48 pub type CrtObjects = BTreeMap<LinkOutputKind, Vec<String>>;
  49
  50 pub(super) fn new(obj_table: &[(LinkOutputKind, &[&str])]) -> CrtObjects {
  51     obj_table.iter().map(|(z, k)| (*z, k.iter().map(|b| b.to_string()).collect())).collect()
  52 }
  53
  54 pub(super) fn all(obj: &str) -> CrtObjects {
  55     new(&[
  56         (LinkOutputKind::DynamicNoPicExe, &[obj]),
  57         (LinkOutputKind::DynamicPicExe, &[obj]),
  58         (LinkOutputKind::StaticNoPicExe, &[obj]),
  59         (LinkOutputKind::StaticPicExe, &[obj]),
  60         (LinkOutputKind::DynamicDylib, &[obj]),
  61         (LinkOutputKind::StaticDylib, &[obj]),
  62     ])
  63 }
  64
  65 pub(super) fn pre_musl_fallback() -> CrtObjects {
  66     new(&[
  67         (LinkOutputKind::DynamicNoPicExe, &["crt1.o", "crti.o"]),
  68         (LinkOutputKind::DynamicPicExe, &["Scrt1.o", "crti.o"]),
  69         (LinkOutputKind::StaticNoPicExe, &["crt1.o", "crti.o"]),
  70         (LinkOutputKind::StaticPicExe, &["rcrt1.o", "crti.o"]),
  71         (LinkOutputKind::DynamicDylib, &["crti.o"]),
  72         (LinkOutputKind::StaticDylib, &["crti.o"]),
  73     ])
  74 }
  75
  76 pub(super) fn post_musl_fallback() -> CrtObjects {
  77     all("crtn.o")
  78 }
  79
  80 pub(super) fn pre_mingw_fallback() -> CrtObjects {
  81     new(&[
  82         (LinkOutputKind::DynamicNoPicExe, &["crt2.o", "rsbegin.o"]),
  83         (LinkOutputKind::DynamicPicExe, &["crt2.o", "rsbegin.o"]),
  84         (LinkOutputKind::StaticNoPicExe, &["crt2.o", "rsbegin.o"]),
  85         (LinkOutputKind::StaticPicExe, &["crt2.o", "rsbegin.o"]),
  86         (LinkOutputKind::DynamicDylib, &["dllcrt2.o", "rsbegin.o"]),
  87         (LinkOutputKind::StaticDylib, &["dllcrt2.o", "rsbegin.o"]),
  88     ])
  89 }
  90
  91 pub(super) fn post_mingw_fallback() -> CrtObjects {
  92     all("rsend.o")
  93 }
  94
  95 pub(super) fn pre_mingw() -> CrtObjects {
  96     all("rsbegin.o")
  97 }
  98
  99 pub(super) fn post_mingw() -> CrtObjects {
 100     all("rsend.o")
 101 }
 102
 103 pub(super) fn pre_wasi_fallback() -> CrtObjects {
 104     new(&[
 105         (LinkOutputKind::DynamicNoPicExe, &["crt1.o"]),
 106         (LinkOutputKind::DynamicPicExe, &["crt1.o"]),
 107         (LinkOutputKind::StaticNoPicExe, &["crt1.o"]),
 108         (LinkOutputKind::StaticPicExe, &["crt1.o"]),
 109         (LinkOutputKind::WasiReactorExe, &["crt1-reactor.o"]),
 110     ])
 111 }
 112
 113 pub(super) fn post_wasi_fallback() -> CrtObjects {
 114     new(&[])
 115 }
 116
 117 /// Which logic to use to determine whether to fall back to the "self-contained" mode or not.
 118 #[derive(Clone, Copy, PartialEq, Hash, Debug)]
 119 pub enum CrtObjectsFallback {
 120     Musl,
 121     Mingw,
 122     Wasm,
 123 }
 124
 125 impl FromStr for CrtObjectsFallback {
 126     type Err = ();
 127
 128     fn from_str(s: &str) -> Result<CrtObjectsFallback, ()> {
 129         Ok(match s {
 130             "musl" => CrtObjectsFallback::Musl,
 131             "mingw" => CrtObjectsFallback::Mingw,
 132             "wasm" => CrtObjectsFallback::Wasm,
 133             _ => return Err(()),
 134         })
 135     }
 136 }
 137
 138 impl ToJson for CrtObjectsFallback {
 139     fn to_json(&self) -> Json {
 140         match *self {
 141             CrtObjectsFallback::Musl => "musl",
 142             CrtObjectsFallback::Mingw => "mingw",
 143             CrtObjectsFallback::Wasm => "wasm",
 144         }
 145         .to_json()
 146     }
 147 }