Add rustc-bin-link-arg and rustc-link-arg custom build options

Both are similar to rustc-cdylib-link-arg. The rustc-bin-link-arg option
adds -C link-arg=... on binary targets. The rustc-link-arg option adds -C
link-arg=... on all supported targets (currently only binaries and cdylib
libraries).

Author: npmccallum

src/cargo/core/compiler/custom_build.rs

@@ -1,5 +1,5 @@
 use super::job::{Freshness, Job, Work};
-use super::{fingerprint, Context, Unit};
+use super::{fingerprint, Context, LinkType, Unit};
 use crate::core::compiler::context::Metadata;
 use crate::core::compiler::job_queue::JobState;
 use crate::core::{profiles::ProfileRoot, PackageId};
@@ -23,7 +23,7 @@ pub struct BuildOutput {
     /// 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>,
+    pub linker_args: Vec<(Option<LinkType>, String)>,
     /// Various `--cfg` flags to pass to the compiler.
     pub cfgs: Vec<String>,
     /// Additional environment variables to run the compiler with.
@@ -535,7 +535,9 @@ 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-cdylib-link-arg" => linker_args.push((Some(LinkType::Cdylib), value)),
+                "rustc-bin-link-arg" => linker_args.push((Some(LinkType::Bin), value)),
+                "rustc-link-arg" => linker_args.push((None, value)),
                 "rustc-cfg" => cfgs.push(value.to_string()),
                 "rustc-env" => env.push(BuildOutput::parse_rustc_env(&value, &whence)?),
                 "warning" => warnings.push(value.to_string()),

src/cargo/core/compiler/mod.rs

@@ -59,6 +59,24 @@ use crate::util::{internal, join_paths, paths, profile};
 
 const RUSTDOC_CRATE_VERSION_FLAG: &str = "--crate-version";
 
+#[derive(Copy, Clone, Hash, Debug, PartialEq, Eq)]
+pub enum LinkType {
+    Cdylib,
+    Bin,
+}
+
+impl From<&super::Target> for Option<LinkType> {
+    fn from(value: &super::Target) -> Self {
+        if value.is_cdylib() {
+            Some(LinkType::Cdylib)
+        } else if value.is_bin() {
+            Some(LinkType::Bin)
+        } else {
+            None
+        }
+    }
+}
+
 /// A glorified callback for executing calls to rustc. Rather than calling rustc
 /// directly, we'll use an `Executor`, giving clients an opportunity to intercept
 /// the build calls.
@@ -196,7 +214,7 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
     // 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 link_type = unit.target.into();
 
     let dep_info_name = match cx.files().metadata(unit) {
         Some(metadata) => format!("{}-{}.d", unit.target.crate_name(), metadata),
@@ -244,7 +262,7 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
                     &script_outputs,
                     &build_scripts,
                     pass_l_flag,
-                    pass_cdylib_link_args,
+                    link_type,
                     current_id,
                 )?;
                 add_plugin_deps(&mut rustc, &script_outputs, &build_scripts, &root_output)?;
@@ -326,7 +344,7 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
         build_script_outputs: &BuildScriptOutputs,
         build_scripts: &BuildScripts,
         pass_l_flag: bool,
-        pass_cdylib_link_args: bool,
+        link_type: Option<LinkType>,
         current_id: PackageId,
     ) -> CargoResult<()> {
         for key in build_scripts.to_link.iter() {
@@ -348,8 +366,14 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
                         rustc.arg("-l").arg(name);
                     }
                 }
-                if pass_cdylib_link_args {
-                    for arg in output.linker_args.iter() {
+
+                if link_type.is_some() {
+                    for arg in output
+                        .linker_args
+                        .iter()
+                        .filter(|x| x.0.is_none() || x.0 == link_type)
+                        .map(|x| &x.1)
+                    {
                         let link_arg = format!("link-arg={}", arg);
                         rustc.arg("-C").arg(link_arg);
                     }

src/cargo/util/config/target.rs

@@ -1,5 +1,5 @@
 use super::{Config, ConfigKey, ConfigRelativePath, OptValue, PathAndArgs, StringList, CV};
-use crate::core::compiler::BuildOutput;
+use crate::core::compiler::{BuildOutput, LinkType};
 use crate::util::CargoResult;
 use serde::Deserialize;
 use std::collections::{BTreeMap, HashMap};
@@ -131,7 +131,18 @@ fn parse_links_overrides(
                 }
                 "rustc-cdylib-link-arg" => {
                     let args = value.list(key)?;
-                    output.linker_args.extend(args.iter().map(|v| v.0.clone()));
+                    let args = args.iter().map(|v| (Some(LinkType::Cdylib), v.0.clone()));
+                    output.linker_args.extend(args);
+                }
+                "rustc-bin-link-arg" => {
+                    let args = value.list(key)?;
+                    let args = args.iter().map(|v| (Some(LinkType::Bin), v.0.clone()));
+                    output.linker_args.extend(args);
+                }
+                "rustc-link-arg" => {
+                    let args = value.list(key)?;
+                    let args = args.iter().map(|v| (None, v.0.clone()));
+                    output.linker_args.extend(args);
                 }
                 "rustc-cfg" => {
                     let list = value.list(key)?;

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

@@ -105,6 +105,10 @@ one detailed below.
 * [`cargo:rustc-env=VAR=VALUE`](#rustc-env) — Sets an environment variable.
 * [`cargo:rustc-cdylib-link-arg=FLAG`](#rustc-cdylib-link-arg) — Passes custom
   flags to a linker for cdylib crates.
+* [`cargo:rustc-bin-link-arg=FLAG`](#rustc-bin-link-arg) — Passes custom
+  flags to a linker for bin crates.
+* [`cargo:rustc-link-arg=FLAG`](#rustc-link-arg) — Passes custom
+  flags to a linker for all supported crates.
 * [`cargo:warning=MESSAGE`](#cargo-warning) — Displays a warning on the
   terminal.
 * [`cargo:KEY=VALUE`](#the-links-manifest-key) — Metadata, used by `links`
@@ -205,6 +209,26 @@ to set the shared library version or the runtime-path.
 
 [link-arg]: ../../rustc/codegen-options/index.md#link-arg
 
+<a id="rustc-bin-link-arg"></a>
+#### `cargo:rustc-bin-link-arg=FLAG`
+
+The `rustc-bin-link-arg` instruction tells Cargo to pass the [`-C
+link-arg=FLAG` option][link-arg] to the compiler, but only when building a
+binary target. Its usage is highly platform specific. It is useful
+to set a linker script or other linker options.
+
+[link-arg]: ../../rustc/codegen-options/index.md#link-arg
+
+<a id="rustc-link-arg"></a>
+#### `cargo:rustc-link-arg=FLAG`
+
+The `rustc-link-arg` instruction tells Cargo to pass the [`-C link-arg=FLAG`
+option][link-arg] to the compiler, but only when building a supported target
+(currently a binary or `cdylib` library). Its usage is highly platform
+specific. It is useful to set the shared library version or linker script.
+
+[link-arg]: ../../rustc/codegen-options/index.md#link-arg
+
 <a id="cargo-warning"></a>
 #### `cargo:warning=MESSAGE`
 
@@ -372,6 +396,8 @@ rustc-flags = "-L /some/path"
 rustc-cfg = ['key="value"']
 rustc-env = {key = "value"}
 rustc-cdylib-link-arg = ["…"]
+rustc-bin-link-arg = ["…"]
+rustc-link-arg = ["…"]
 metadata_key1 = "value"
 metadata_key2 = "value"
 ```