Add tests and warnings for -Zextra-link-arg.

src/cargo/core/compiler/custom_build.rs

@@ -289,6 +289,8 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
     paths::create_dir_all(&script_dir)?;
     paths::create_dir_all(&script_out_dir)?;
 
+    let extra_link_arg = cx.bcx.config.cli_unstable().extra_link_arg;
+
     // Prepare the unit of "dirty work" which will actually run the custom build
     // command.
     //
@@ -392,8 +394,13 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
         paths::set_file_time_no_err(output_file, timestamp);
         paths::write(&err_file, &output.stderr)?;
         paths::write(&root_output_file, util::path2bytes(&script_out_dir)?)?;
-        let parsed_output =
-            BuildOutput::parse(&output.stdout, &pkg_name, &script_out_dir, &script_out_dir)?;
+        let parsed_output = BuildOutput::parse(
+            &output.stdout,
+            &pkg_name,
+            &script_out_dir,
+            &script_out_dir,
+            extra_link_arg,
+        )?;
 
         if json_messages {
             emit_build_output(state, &parsed_output, script_out_dir.as_path(), id);
@@ -417,6 +424,7 @@ fn build_work(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Job> {
                 &pkg_name,
                 &prev_script_out_dir,
                 &script_out_dir,
+                extra_link_arg,
             )?,
         };
 
@@ -466,6 +474,7 @@ impl BuildOutput {
         pkg_name: &str,
         script_out_dir_when_generated: &Path,
         script_out_dir: &Path,
+        extra_link_arg: bool,
     ) -> CargoResult<BuildOutput> {
         let contents = paths::read_bytes(path)?;
         BuildOutput::parse(
@@ -473,6 +482,7 @@ impl BuildOutput {
             pkg_name,
             script_out_dir_when_generated,
             script_out_dir,
+            extra_link_arg,
         )
     }
 
@@ -483,6 +493,7 @@ impl BuildOutput {
         pkg_name: &str,
         script_out_dir_when_generated: &Path,
         script_out_dir: &Path,
+        extra_link_arg: bool,
     ) -> CargoResult<BuildOutput> {
         let mut library_paths = Vec::new();
         let mut library_links = Vec::new();
@@ -536,8 +547,20 @@ 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((Some(LinkType::Cdylib), value)),
-                "rustc-bin-link-arg" => linker_args.push((Some(LinkType::Bin), value)),
-                "rustc-link-arg" => linker_args.push((None, value)),
+                "rustc-bin-link-arg" => {
+                    if extra_link_arg {
+                        linker_args.push((Some(LinkType::Bin), value));
+                    } else {
+                        warnings.push(format!("cargo:{} requires -Zextra-link-arg flag", key));
+                    }
+                }
+                "rustc-link-arg" => {
+                    if extra_link_arg {
+                        linker_args.push((None, value));
+                    } else {
+                        warnings.push(format!("cargo:{} requires -Zextra-link-arg flag", key));
+                    }
+                }
                 "rustc-cfg" => cfgs.push(value.to_string()),
                 "rustc-env" => env.push(BuildOutput::parse_rustc_env(&value, &whence)?),
                 "warning" => warnings.push(value.to_string()),
@@ -786,12 +809,15 @@ fn prev_build_output(cx: &mut Context<'_, '_>, unit: &Unit) -> (Option<BuildOutp
         .and_then(|bytes| util::bytes2path(&bytes))
         .unwrap_or_else(|_| script_out_dir.clone());
 
+    let extra_link_arg = cx.bcx.config.cli_unstable().extra_link_arg;
+
     (
         BuildOutput::parse_file(
             &output_file,
             &unit.pkg.to_string(),
             &prev_script_out_dir,
             &script_out_dir,
+            extra_link_arg,
         )
         .ok(),
         prev_script_out_dir,

src/cargo/core/compiler/mod.rs

@@ -215,7 +215,6 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
     // don't pass the `-l` flags.
     let pass_l_flag = unit.target.is_lib() || !unit.pkg.targets().iter().any(|t| t.is_lib());
     let link_type = (&unit.target).into();
-    let extra_link_arg = cx.bcx.config.cli_unstable().extra_link_arg;
 
     let dep_info_name = match cx.files().metadata(unit) {
         Some(metadata) => format!("{}-{}.d", unit.target.crate_name(), metadata),
@@ -264,7 +263,6 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
                     &build_scripts,
                     pass_l_flag,
                     link_type,
-                    extra_link_arg,
                     current_id,
                 )?;
                 add_plugin_deps(&mut rustc, &script_outputs, &build_scripts, &root_output)?;
@@ -347,7 +345,6 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
         build_scripts: &BuildScripts,
         pass_l_flag: bool,
         link_type: Option<LinkType>,
-        extra_link_arg: bool,
         current_id: PackageId,
     ) -> CargoResult<()> {
         for key in build_scripts.to_link.iter() {
@@ -370,14 +367,11 @@ fn rustc(cx: &mut Context<'_, '_>, unit: &Unit, exec: &Arc<dyn Executor>) -> Car
                     }
                 }
                 if link_type.is_some() {
-                    output
-                        .linker_args
-                        .iter()
-                        .filter(|x| x.0.is_none() || x.0 == link_type)
-                        .filter(|x| x.0 == Some(LinkType::Cdylib) || extra_link_arg)
-                        .for_each(|x| {
-                            rustc.arg("-C").arg(format!("link-arg={}", x.1));
-                        });
+                    for (lt, arg) in &output.linker_args {
+                        if lt.is_none() || *lt == link_type {
+                            rustc.arg("-C").arg(format!("link-arg={}", arg));
+                        }
+                    }
                 }
             }
         }

tests/testsuite/build_script_extra_link_arg.rs

@@ -0,0 +1,72 @@
+//! Tests for -Zextra-link-arg.
+
+use cargo_test_support::{basic_bin_manifest, project};
+
+#[cargo_test]
+fn build_script_extra_bin_link_args() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file("src/main.rs", "fn main() {}")
+        .file(
+            "build.rs",
+            r#"
+                fn main() {
+                    println!("cargo:rustc-bin-link-arg=--this-is-a-bogus-flag");
+                }
+            "#,
+        )
+        .build();
+
+    p.cargo("build -Zextra-link-arg -v")
+        .masquerade_as_nightly_cargo()
+        .with_status(101)
+        .with_stderr_contains(
+            "[RUNNING] `rustc --crate-name foo [..]-C link-arg=--this-is-a-bogus-flag[..]",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn build_script_extra_link_args() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file("src/main.rs", "fn main() {}")
+        .file(
+            "build.rs",
+            r#"
+                fn main() {
+                    println!("cargo:rustc-link-arg=--this-is-a-bogus-flag");
+                }
+            "#,
+        )
+        .build();
+
+    p.cargo("build -Zextra-link-arg -v")
+        .masquerade_as_nightly_cargo()
+        .with_status(101)
+        .with_stderr_contains(
+            "[RUNNING] `rustc --crate-name foo [..]-C link-arg=--this-is-a-bogus-flag[..]",
+        )
+        .run();
+}
+
+#[cargo_test]
+fn build_script_extra_link_args_warn_on_stable() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file("src/main.rs", "fn main() {}")
+        .file(
+            "build.rs",
+            r#"
+                fn main() {
+                    println!("cargo:rustc-link-arg=--this-is-a-bogus-flag");
+                }
+            "#,
+        )
+        .build();
+
+    p.cargo("build -vv")
+        .with_status(0)
+        .with_stderr_contains("warning: cargo:rustc-link-arg requires -Zextra-link-arg flag")
+        .run();
+}

tests/testsuite/main.rs

@@ -20,6 +20,7 @@ mod build;
 mod build_plan;
 mod build_script;
 mod build_script_env;
+mod build_script_extra_link_arg;
 mod cache_messages;
 mod cargo_alias_config;
 mod cargo_command;