wip: split out linker-info from linker-messages

jyn514 · jyn514 · commit c666de87d9f9 · 2025-12-12T17:32:41.000-05:00
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -22,6 +22,7 @@ use rustc_errors::{DiagCtxtHandle, LintDiagnostic};
 use rustc_fs_util::{TempDirBuilder, fix_windows_verbatim_for_gcc, try_canonicalize};
 use rustc_hir::attrs::NativeLibKind;
 use rustc_hir::def_id::{CrateNum, LOCAL_CRATE};
+use rustc_lint_defs::builtin::LINKER_INFO;
 use rustc_macros::LintDiagnostic;
 use rustc_metadata::fs::{METADATA_FILENAME, copy_to_stdout, emit_wrapper_file};
 use rustc_metadata::{
@@ -60,7 +61,8 @@ use super::rpath::{self, RPathConfig};
 use super::{apple, versioned_llvm_target};
 use crate::base::needs_allocator_shim_for_linking;
 use crate::{
-    CodegenLintLevels, CodegenResults, CompiledModule, CrateInfo, NativeLib, errors, looks_like_rust_object_file
+    CodegenLintLevels, CodegenResults, CompiledModule, CrateInfo, NativeLib, errors,
+    looks_like_rust_object_file,
 };
 
 pub fn ensure_removed(dcx: DiagCtxtHandle<'_>, path: &Path) {
@@ -678,37 +680,106 @@ fn is_msvc_link_exe(sess: &Session) -> bool {
         && linker_path.to_str() == Some("link.exe")
 }
 
+fn is_macos_ld(sess: &Session) -> bool {
+    let (_, flavor) = linker_and_flavor(sess);
+    sess.target.is_like_darwin && matches!(flavor, LinkerFlavor::Darwin(_, Lld::No))
+}
+
+fn is_windows_gnu_ld(sess: &Session) -> bool {
+    let (_, flavor) = linker_and_flavor(sess);
+    sess.target.is_like_windows
+        && !sess.target.is_like_msvc
+        && matches!(flavor, LinkerFlavor::Gnu(_, Lld::No))
+}
+
 fn report_linker_output(sess: &Session, levels: CodegenLintLevels, stdout: &[u8], stderr: &[u8]) {
-    let escaped_stderr = escape_string(&stderr);
+    let mut escaped_stderr = escape_string(&stderr);
     let mut escaped_stdout = escape_string(&stdout);
+    let mut linker_info = String::new();
+
     info!("linker stderr:\n{}", &escaped_stderr);
     info!("linker stdout:\n{}", &escaped_stdout);
 
+    fn for_each(bytes: &[u8], mut f: impl FnMut(&str, &mut String)) -> String {
+        let mut output = String::new();
+        if let Ok(str) = str::from_utf8(bytes) {
+            info!("line: {str}");
+            output = String::with_capacity(str.len());
+            for line in str.lines() {
+                f(line.trim(), &mut output);
+            }
+        }
+        escape_string(output.trim().as_bytes())
+    }
+
     // Hide some progress messages from link.exe that we don't care about.
     // See https://github.com/chromium/chromium/blob/bfa41e41145ffc85f041384280caf2949bb7bd72/build/toolchain/win/tool_wrapper.py#L144-L146
     if is_msvc_link_exe(sess) {
-        if let Ok(str) = str::from_utf8(&stdout) {
-            let mut output = String::with_capacity(str.len());
-            for line in str.lines() {
-                if line.starts_with("   Creating library")
-                    || line.starts_with("Generating code")
-                        || line.starts_with("Finished generating code")
-                {
-                    continue;
-                } else {
-                    output += line;
-                    output += "\r\n"
-                }
+        escaped_stdout = for_each(&stdout, |line, output| {
+            if line.starts_with("   Creating library")
+                || line.starts_with("Generating code")
+                || line.starts_with("Finished generating code")
+            {
+                linker_info += line;
+                linker_info += "\r\n";
+            } else {
+                *output += line;
+                *output += "\r\n"
             }
-            escaped_stdout = escape_string(output.trim().as_bytes())
-        }
+        });
+    } else if is_macos_ld(sess) {
+        let deployment_mismatch = |line: &str| {
+            line.starts_with("ld: warning: object file (")
+                && line.contains("was built for newer 'macOS' version")
+                && line.contains("than being linked")
+        };
+        let search_path = |line: &str| {
+            line.starts_with("ld: warning: search path '") && line.ends_with("' not found")
+        };
+        escaped_stderr = for_each(&stderr, |line, output| {
+            if line.starts_with("ld: warning: ignoring duplicate libraries: ")
+                || deployment_mismatch(line)
+                || search_path(line)
+            {
+                linker_info += line;
+                linker_info += "\n";
+            } else {
+                *output += line;
+                *output += "\n"
+            }
+        });
+    } else if is_windows_gnu_ld(sess) {
+        let mut saw_exclude_symbol = false;
+        let exclude_symbols = |line: &str| {
+            line.starts_with("Warning: .drectve `-exclude-symbols:")
+                && line.ends_with("' unrecognized")
+        };
+        // FIXME: are we sure this is stderr and not stdout?
+        escaped_stderr = for_each(&stderr, |line, output| {
+            if exclude_symbols(line) {
+                saw_exclude_symbol = true;
+                linker_info += line;
+                linker_info += "\n";
+            } else if saw_exclude_symbol && line == "Warning: corrupt .drectve at end of def file" {
+                linker_info += line;
+                linker_info += "\n";
+            } else {
+                *output += line;
+                *output += "\n"
+            }
+        });
     }
 
     let lint_msg = |msg| {
         lint_level(sess, LINKER_MESSAGES, levels.linker_messages, None, |diag| {
             LinkerOutput { inner: msg }.decorate_lint(diag)
         })
     };
+    let lint_info = |msg| {
+        lint_level(sess, LINKER_INFO, levels.linker_info, None, |diag| {
+            LinkerOutput { inner: msg }.decorate_lint(diag)
+        })
+    };
 
     if !escaped_stderr.is_empty() {
         // We already print `warning:` at the start of the diagnostic. Remove it from the linker output if present.
@@ -721,6 +792,9 @@ fn report_linker_output(sess: &Session, levels: CodegenLintLevels, stdout: &[u8]
     if !escaped_stdout.is_empty() {
         lint_msg(format!("linker stdout: {}", escaped_stdout))
     }
+    if !linker_info.is_empty() {
+        lint_info(linker_info);
+    }
 }
 
 /// Create a dynamic library or executable.
@@ -960,7 +1034,12 @@ fn link_natively(
                 sess.dcx().abort_if_errors();
             }
 
-            report_linker_output(sess, codegen_results.crate_info.lint_levels, &prog.stdout, &prog.stderr);
+            report_linker_output(
+                sess,
+                codegen_results.crate_info.lint_levels,
+                &prog.stdout,
+                &prog.stderr,
+            );
         }
         Err(e) => {
             let linker_not_found = e.kind() == io::ErrorKind::NotFound;
diff --git a/compiler/rustc_codegen_ssa/src/lib.rs b/compiler/rustc_codegen_ssa/src/lib.rs
@@ -26,6 +26,7 @@ use rustc_data_structures::unord::UnordMap;
 use rustc_hir::CRATE_HIR_ID;
 use rustc_hir::attrs::{CfgEntry, NativeLibKind};
 use rustc_hir::def_id::CrateNum;
+use rustc_lint_defs::builtin::LINKER_INFO;
 use rustc_macros::{Decodable, Encodable, HashStable};
 use rustc_metadata::EncodedMetadata;
 use rustc_middle::dep_graph::WorkProduct;
@@ -360,10 +361,14 @@ impl CodegenResults {
 #[derive(Copy, Clone, Debug, Encodable, Decodable)]
 pub struct CodegenLintLevels {
     linker_messages: LevelAndSource,
+    linker_info: LevelAndSource,
 }
 
 impl CodegenLintLevels {
     pub fn from_tcx(tcx: TyCtxt<'_>) -> Self {
-        Self { linker_messages: tcx.lint_level_at_node(LINKER_MESSAGES, CRATE_HIR_ID) }
+        Self {
+            linker_messages: tcx.lint_level_at_node(LINKER_MESSAGES, CRATE_HIR_ID),
+            linker_info: tcx.lint_level_at_node(LINKER_INFO, CRATE_HIR_ID),
+        }
     }
 }
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
@@ -58,6 +58,7 @@ declare_lint_pass! {
         LARGE_ASSIGNMENTS,
         LATE_BOUND_LIFETIME_ARGUMENTS,
         LEGACY_DERIVE_HELPERS,
+        LINKER_INFO,
         LINKER_MESSAGES,
         LONG_RUNNING_CONST_EVAL,
         LOSSY_PROVENANCE_CASTS,
@@ -4010,10 +4011,44 @@ declare_lint! {
     /// and actionable warning of similar quality to our other diagnostics. See this tracking
     /// issue for more details: <https://github.com/rust-lang/rust/issues/136096>.
     pub LINKER_MESSAGES,
-    Allow,
+    Warn,
     "warnings emitted at runtime by the target-specific linker program"
 }
 
+declare_lint! {
+    /// The `linker_info` lint forwards warnings from the linker that are known to be informational-only.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,ignore (needs CLI args, platform-specific)
+    /// #[warn(linker_info)]
+    /// fn main () {}
+    /// ```
+    ///
+    /// On MacOS, using `-C link-arg=-lc` and the default linker, this will produce
+    ///
+    /// ```text
+    /// warning: linker stderr: ld: ignoring duplicate libraries: '-lc'
+    ///   |
+    /// note: the lint level is defined here
+    ///  --> ex.rs:1:9
+    ///   |
+    /// 1 | #![warn(linker_info)]
+    ///   |         ^^^^^^^^^^^^^^^
+    /// ```
+    ///
+    /// ### Explanation
+    ///
+    /// Many linkers are very "chatty" and print lots of information that is not necessarily
+    /// indicative of an issue. This output has been ignored for many years and is often not
+    /// actionable by developers. It is silenced unless the developer specifically requests for it
+    /// to be printed. See this tracking issue for more details:
+    /// <https://github.com/rust-lang/rust/issues/136096>.
+    pub LINKER_INFO,
+    Allow,
+    "linker warnings known to be informational-only and not indicative of a problem"
+}
+
 declare_lint! {
     /// The `named_arguments_used_positionally` lint detects cases where named arguments are only
     /// used positionally in format strings. This usage is valid but potentially very confusing.
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
@@ -642,7 +642,7 @@ passes_unused_empty_lints_note =
     attribute `{$name}` with an empty list has no effect
 
 passes_unused_linker_messages_note =
-    the `linker_messages` lint can only be controlled at the root of a crate that needs to be linked
+    the `linker_messages` and `linker_info` lints can only be controlled at the root of a crate that needs to be linked
 
 passes_unused_multiple =
     multiple `{$name}` attributes
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
@@ -1947,7 +1947,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         } else if attr.has_any_name(&[sym::allow, sym::warn, sym::deny, sym::forbid, sym::expect])
             && let Some(meta) = attr.meta_item_list()
             && meta.iter().any(|meta| {
-                meta.meta_item().map_or(false, |item| item.path == sym::linker_messages)
+                meta.meta_item().map_or(false, |item| {
+                    item.path == sym::linker_messages || item.path == sym::linker_info
+                })
             })
         {
             if hir_id != CRATE_HIR_ID {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
@@ -1328,6 +1328,7 @@ symbols! {
         link_section,
         linkage,
         linker,
+        linker_info,
         linker_messages,
         linkonce,
         linkonce_odr,
diff --git a/tests/ui/linking/macos-ignoring-duplicate.rs b/tests/ui/linking/macos-ignoring-duplicate.rs
@@ -0,0 +1,6 @@
+//@ only-apple
+//@ compile-flags: -C link-arg=-lc -C link-arg=-lc
+//@ build-fail
+#![deny(linker_info)]
+//~? ERROR ignoring duplicate libraries
+fn main() {}
diff --git a/tests/ui/linking/macos-ignoring-duplicate.stderr b/tests/ui/linking/macos-ignoring-duplicate.stderr
@@ -0,0 +1,11 @@
+error: ld: warning: ignoring duplicate libraries: '-lc'
+       
+   |
+note: the lint level is defined here
+  --> $DIR/macos-ignoring-duplicate.rs:4:9
+   |
+LL | #![deny(linker_info)]
+   |         ^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/linking/macos-search-path.rs b/tests/ui/linking/macos-search-path.rs
@@ -0,0 +1,6 @@
+//@ only-apple
+//@ compile-flags: -C link-arg=-Wl,-L/no/such/file/or/directory
+//@ build-fail
+#![deny(linker_info)]
+//~? ERROR search path
+fn main() {}
diff --git a/tests/ui/linking/macos-search-path.stderr b/tests/ui/linking/macos-search-path.stderr
@@ -0,0 +1,11 @@
+error: ld: warning: search path '/no/such/file/or/directory' not found
+       
+   |
+note: the lint level is defined here
+  --> $DIR/macos-search-path.rs:4:9
+   |
+LL | #![deny(linker_info)]
+   |         ^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
