Add cargo:rustc-link-arg to pass custom linker arguments

src/cargo/core/compiler/build_context/mod.rs

@@ -223,6 +223,7 @@ impl TargetConfig {
  let mut output = BuildOutput {
  library_paths: Vec::new(),
  library_links: Vec::new(),
+ linker_args: Vec::new(),
  cfgs: Vec::new(),
  env: Vec::new(),
  metadata: Vec::new(),
@@ -258,6 +259,12 @@ impl TargetConfig {
  .library_paths
  .extend(list.iter().map(|v| PathBuf::from(&v.0)));
  }
+ "rustc-cdylib-link-arg" => {
+ let args = value.list(k)?;
+ output
+ .linker_args
+ .extend(args.iter().map(|v| v.0.clone()));
+ }
  "rustc-cfg" => {
  let list = value.list(k)?;
  output.cfgs.extend(list.iter().map(|v| v.0.clone()));

src/cargo/core/compiler/custom_build.rs

@@ -21,6 +21,8 @@ pub struct BuildOutput {
  pub library_paths: Vec<PathBuf>,
  /// Names and link kinds of libraries, suitable for the `-l` flag.
  pub library_links: Vec<String>,
+ /// Linker arguments suitable to be passed to `-C link-arg=<args>`
+ pub linker_args: Vec<String>,
  /// Various `--cfg` flags to pass to the compiler.
  pub cfgs: Vec<String>,
  /// Additional environment variables to run the compiler with.
@@ -437,6 +439,7 @@ impl BuildOutput {
  ) -> CargoResult<BuildOutput> {
  let mut library_paths = Vec::new();
  let mut library_links = Vec::new();
+ let mut linker_args = Vec::new();
  let mut cfgs = Vec::new();
  let mut env = Vec::new();
  let mut metadata = Vec::new();
@@ -484,6 +487,7 @@ impl BuildOutput {
  }
  "rustc-link-lib" => library_links.push(value.to_string()),
  "rustc-link-search" => library_paths.push(PathBuf::from(value)),
+ "rustc-cdylib-link-arg" => linker_args.push(value.to_string()),
  "rustc-cfg" => cfgs.push(value.to_string()),
  "rustc-env" => env.push(BuildOutput::parse_rustc_env(&value, &whence)?),
  "warning" => warnings.push(value.to_string()),
@@ -496,6 +500,7 @@ impl BuildOutput {
  Ok(BuildOutput {
  library_paths,
  library_links,
+ linker_args,
  cfgs,
  env,
  metadata,

src/cargo/core/compiler/mod.rs

@@ -211,6 +211,7 @@ fn rustc<'a, 'cfg>(
  // If we are a binary and the package also contains a library, then we
  // don't pass the `-l` flags.
  let pass_l_flag = unit.target.is_lib() || !unit.pkg.targets().iter().any(|t| t.is_lib());
+ let pass_cdylib_link_args = unit.target.is_cdylib();
  let do_rename = unit.target.allows_underscores() && !unit.mode.is_any_test();
  let real_name = unit.target.name().to_string();
  let crate_name = unit.target.crate_name();
@@ -257,6 +258,7 @@ fn rustc<'a, 'cfg>(
  &build_state,
  &build_deps,
  pass_l_flag,
+ pass_cdylib_link_args,
  current_id,
  )?;
  add_plugin_deps(&mut rustc, &build_state, &build_deps, &root_output)?;
@@ -346,6 +348,7 @@ fn rustc<'a, 'cfg>(
  build_state: &BuildMap,
  build_scripts: &BuildScripts,
  pass_l_flag: bool,
+ pass_cdylib_link_args: bool,
  current_id: PackageId,
  ) -> CargoResult<()> {
  for key in build_scripts.to_link.iter() {
@@ -367,6 +370,12 @@ fn rustc<'a, 'cfg>(
  rustc.arg("-l").arg(name);
  }
  }
+ if pass_cdylib_link_args {
+ for arg in output.linker_args.iter() {
+ let link_arg = format!("link-arg={}", arg);
+ rustc.arg("-C").arg(link_arg);
+ }
+ }
  }
  }
  Ok(())

src/doc/src/reference/build-scripts.md

@@ -62,6 +62,7 @@ cargo:rustc-link-lib=static=foo
 cargo:rustc-link-search=native=/path/to/foo
 cargo:rustc-cfg=foo
 cargo:rustc-env=FOO=bar
+cargo:rustc-cdylib-link-arg=-Wl,-soname,libfoo.so.1.2.3
 # arbitrary user-defined metadata
 cargo:root=/path/to/foo
 cargo:libdir=/path/to/foo/lib
@@ -93,6 +94,9 @@ crate is built:
  This is useful for embedding additional metadata in crate's code,
  such as the hash of Git HEAD or the unique identifier of a continuous
  integration server.
+* `rustc-cdylib-link-arg=FLAG` is a flag passed to the compiler as
+ `-C link-arg=FLAG` when building a `cdylib`. Its usage is highly platform
+ specific. It is useful to set the shared library version or the runtime-path.
 * `rerun-if-changed=PATH` is a path to a file or directory which indicates that
  the build script should be re-run if it changes (detected by a more-recent
  last-modified timestamp on the file). Normally build scripts are re-run if