Rollup merge of #113780 - dtolnay:printkindpath, r=b-naber

Support `--print KIND=PATH` command line syntax

As is already done for `--emit KIND=PATH` and `-L KIND=PATH`.

In the discussion of #110785, it was pointed out that `--print KIND=PATH` is nicer than trying to apply the single global `-o` path to `--print`'s output, because in general there can be multiple print requests within a single rustc invocation, and anyway `-o` would already be used for a different meaning in the case of `link-args` and `native-static-libs`.

I am interested in using `--print cfg=PATH` in Buck2. Currently Buck2 works around the lack of support for `--print KIND=PATH` by [indirecting through a Python wrapper script](d43cf3a51a/prelude/rust/tools/get_rustc_cfg.py) to redirect rustc's stdout into the location dictated by the build system.

From skimming Cargo's usages of `--print`, it definitely seems like it would benefit from `--print KIND=PATH` too. Currently it is working around the lack of this by inserting `--crate-name=___ --print=crate-name` so that it can look for a line containing `___` as a delimiter between the 2 other `--print` informations it actually cares about. This is commented as a "HACK" and "abuse". 31eda6f7c3/src/cargo/core/compiler/build_context/target_info.rs (L242) (FYI `@weihanglo` as you dealt with this recently in https://github.com/rust-lang/cargo/pull/11633.)

Mentioning reviewers active in #110785: `@fee1-dead` `@jyn514` `@bjorn3`

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -12,8 +12,8 @@ use rustc_metadata::fs::{copy_to_stdout, emit_wrapper_file, METADATA_FILENAME};
 use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::dependency_format::Linkage;
 use rustc_middle::middle::exported_symbols::SymbolExportKind;
-use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, Strip};
-use rustc_session::config::{OutputFilenames, OutputType, PrintRequest, SplitDwarfKind};
+use rustc_session::config::{self, CFGuard, CrateType, DebugInfo, OutFileName, Strip};
+use rustc_session::config::{OutputFilenames, OutputType, PrintKind, SplitDwarfKind};
 use rustc_session::cstore::DllImport;
 use rustc_session::output::{check_file_is_writeable, invalid_output_for_target, out_filename};
 use rustc_session::search_paths::PathKind;
@@ -596,8 +596,10 @@ fn link_staticlib<'a>(
 
     all_native_libs.extend_from_slice(&codegen_results.crate_info.used_libraries);
 
-    if sess.opts.prints.contains(&PrintRequest::NativeStaticLibs) {
-        print_native_static_libs(sess, &all_native_libs, &all_rust_dylibs);
+    for print in &sess.opts.prints {
+        if print.kind == PrintKind::NativeStaticLibs {
+            print_native_static_libs(sess, &print.out, &all_native_libs, &all_rust_dylibs);
+        }
     }
 
     Ok(())
@@ -744,8 +746,11 @@ fn link_natively<'a>(
         cmd.env_remove(k.as_ref());
     }
 
-    if sess.opts.prints.contains(&PrintRequest::LinkArgs) {
-        println!("{:?}", &cmd);
+    for print in &sess.opts.prints {
+        if print.kind == PrintKind::LinkArgs {
+            let content = format!("{:?}", cmd);
+            print.out.overwrite(&content, sess);
+        }
     }
 
     // May have not found libraries in the right formats.
@@ -1386,6 +1391,7 @@ enum RlibFlavor {
 
 fn print_native_static_libs(
     sess: &Session,
+    out: &OutFileName,
     all_native_libs: &[NativeLib],
     all_rust_dylibs: &[&Path],
 ) {
@@ -1459,11 +1465,22 @@ fn print_native_static_libs(
             lib_args.push(format!("-l{}", lib));
         }
     }
-    if !lib_args.is_empty() {
-        sess.emit_note(errors::StaticLibraryNativeArtifacts);
-        // Prefix for greppability
-        // Note: This must not be translated as tools are allowed to depend on this exact string.
-        sess.note_without_error(format!("native-static-libs: {}", &lib_args.join(" ")));
+
+    match out {
+        OutFileName::Real(path) => {
+            out.overwrite(&lib_args.join(" "), sess);
+            if !lib_args.is_empty() {
+                sess.emit_note(errors::StaticLibraryNativeArtifactsToFile { path });
+            }
+        }
+        OutFileName::Stdout => {
+            if !lib_args.is_empty() {
+                sess.emit_note(errors::StaticLibraryNativeArtifacts);
+                // Prefix for greppability
+                // Note: This must not be translated as tools are allowed to depend on this exact string.
+                sess.note_without_error(format!("native-static-libs: {}", &lib_args.join(" ")));
+            }
+        }
     }
 }
 

compiler/rustc_codegen_ssa/src/errors.rs

@@ -455,6 +455,12 @@ pub struct LinkerFileStem;
 #[diag(codegen_ssa_static_library_native_artifacts)]
 pub struct StaticLibraryNativeArtifacts;
 
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_static_library_native_artifacts_to_file)]
+pub struct StaticLibraryNativeArtifactsToFile<'a> {
+    pub path: &'a Path,
+}
+
 #[derive(Diagnostic)]
 #[diag(codegen_ssa_link_script_unavailable)]
 pub struct LinkScriptUnavailable;

compiler/rustc_codegen_ssa/src/traits/backend.rs

@@ -23,6 +23,8 @@ use rustc_span::symbol::Symbol;
 use rustc_target::abi::call::FnAbi;
 use rustc_target::spec::Target;
 
+use std::fmt;
+
 pub trait BackendTypes {
     type Value: CodegenObject;
     type Function: CodegenObject;
@@ -61,7 +63,7 @@ pub trait CodegenBackend {
     fn locale_resource(&self) -> &'static str;
 
     fn init(&self, _sess: &Session) {}
-    fn print(&self, _req: PrintRequest, _sess: &Session) {}
+    fn print(&self, _req: &PrintRequest, _out: &mut dyn PrintBackendInfo, _sess: &Session) {}
     fn target_features(&self, _sess: &Session, _allow_unstable: bool) -> Vec<Symbol> {
         vec![]
     }
@@ -162,3 +164,19 @@ pub trait ExtraBackendMethods:
         std::thread::Builder::new().name(name).spawn(f)
     }
 }
+
+pub trait PrintBackendInfo {
+    fn infallible_write_fmt(&mut self, args: fmt::Arguments<'_>);
+}
+
+impl PrintBackendInfo for String {
+    fn infallible_write_fmt(&mut self, args: fmt::Arguments<'_>) {
+        fmt::Write::write_fmt(self, args).unwrap();
+    }
+}
+
+impl dyn PrintBackendInfo + '_ {
+    pub fn write_fmt(&mut self, args: fmt::Arguments<'_>) {
+        self.infallible_write_fmt(args);
+    }
+}

compiler/rustc_codegen_ssa/src/traits/mod.rs

@@ -30,7 +30,9 @@ mod write;
 
 pub use self::abi::AbiBuilderMethods;
 pub use self::asm::{AsmBuilderMethods, AsmMethods, GlobalAsmOperandRef, InlineAsmOperandRef};
-pub use self::backend::{Backend, BackendTypes, CodegenBackend, ExtraBackendMethods};
+pub use self::backend::{
+    Backend, BackendTypes, CodegenBackend, ExtraBackendMethods, PrintBackendInfo,
+};
 pub use self::builder::{BuilderMethods, OverflowOp};
 pub use self::consts::ConstMethods;
 pub use self::coverageinfo::CoverageInfoBuilderMethods;