Rollup merge of rust-lang#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 rust-lang#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](https://github.com/facebook/buck2/blob/d43cf3a51a31f00be2c2248e78271b0fef0452b4/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". https://github.com/rust-lang/cargo/blob/31eda6f7c360d9911f853b3014e057db61238f3e/src/cargo/core/compiler/build_context/target_info.rs#L242 (FYI `@weihanglo` as you dealt with this recently in rust-lang/cargo#11633.)

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

compiler/rustc_codegen_llvm/src/lib.rs

@@ -40,7 +40,7 @@ use rustc_metadata::EncodedMetadata;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
-use rustc_session::config::{OptLevel, OutputFilenames, PrintRequest};
+use rustc_session::config::{OptLevel, OutputFilenames, PrintKind, PrintRequest};
 use rustc_session::Session;
 use rustc_span::symbol::Symbol;
 
@@ -262,10 +262,10 @@ impl CodegenBackend for LlvmCodegenBackend {
             |tcx, ()| llvm_util::global_llvm_features(tcx.sess, true)
     }
 
-    fn print(&self, req: PrintRequest, sess: &Session) {
-        match req {
-            PrintRequest::RelocationModels => {
-                println!("Available relocation models:");
+    fn print(&self, req: &PrintRequest, out: &mut dyn PrintBackendInfo, sess: &Session) {
+        match req.kind {
+            PrintKind::RelocationModels => {
+                writeln!(out, "Available relocation models:");
                 for name in &[
                     "static",
                     "pic",
@@ -276,26 +276,27 @@ impl CodegenBackend for LlvmCodegenBackend {
                     "ropi-rwpi",
                     "default",
                 ] {
-                    println!("    {}", name);
+                    writeln!(out, "    {}", name);
                 }
-                println!();
+                writeln!(out);
             }
-            PrintRequest::CodeModels => {
-                println!("Available code models:");
+            PrintKind::CodeModels => {
+                writeln!(out, "Available code models:");
                 for name in &["tiny", "small", "kernel", "medium", "large"] {
-                    println!("    {}", name);
+                    writeln!(out, "    {}", name);
                 }
-                println!();
+                writeln!(out);
             }
-            PrintRequest::TlsModels => {
-                println!("Available TLS models:");
+            PrintKind::TlsModels => {
+                writeln!(out, "Available TLS models:");
                 for name in &["global-dynamic", "local-dynamic", "initial-exec", "local-exec"] {
-                    println!("    {}", name);
+                    writeln!(out, "    {}", name);
                 }
-                println!();
+                writeln!(out);
             }
-            PrintRequest::StackProtectorStrategies => {
-                println!(
+            PrintKind::StackProtectorStrategies => {
+                writeln!(
+                    out,
                     r#"Available stack protector strategies:
     all
         Generate stack canaries in all functions.
@@ -319,7 +320,7 @@ impl CodegenBackend for LlvmCodegenBackend {
 "#
                 );
             }
-            req => llvm_util::print(req, sess),
+            _other => llvm_util::print(req, out, sess),
         }
     }
 

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2280,7 +2280,12 @@ extern "C" {
 
     pub fn LLVMRustHasFeature(T: &TargetMachine, s: *const c_char) -> bool;
 
-    pub fn LLVMRustPrintTargetCPUs(T: &TargetMachine, cpu: *const c_char);
+    pub fn LLVMRustPrintTargetCPUs(
+        T: &TargetMachine,
+        cpu: *const c_char,
+        print: unsafe extern "C" fn(out: *mut c_void, string: *const c_char, len: usize),
+        out: *mut c_void,
+    );
     pub fn LLVMRustGetTargetFeaturesCount(T: &TargetMachine) -> size_t;
     pub fn LLVMRustGetTargetFeature(
         T: &TargetMachine,

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -8,16 +8,17 @@ use libc::c_int;
 use rustc_codegen_ssa::target_features::{
     supported_target_features, tied_target_features, RUSTC_SPECIFIC_FEATURES,
 };
+use rustc_codegen_ssa::traits::PrintBackendInfo;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::small_c_str::SmallCStr;
 use rustc_fs_util::path_to_c_string;
 use rustc_middle::bug;
-use rustc_session::config::PrintRequest;
+use rustc_session::config::{PrintKind, PrintRequest};
 use rustc_session::Session;
 use rustc_span::symbol::Symbol;
 use rustc_target::spec::{MergeFunctions, PanicStrategy};
-use std::ffi::{CStr, CString};
 
+use std::ffi::{c_char, c_void, CStr, CString};
 use std::path::Path;
 use std::ptr;
 use std::slice;
@@ -350,7 +351,7 @@ fn llvm_target_features(tm: &llvm::TargetMachine) -> Vec<(&str, &str)> {
     ret
 }
 
-fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
+fn print_target_features(out: &mut dyn PrintBackendInfo, sess: &Session, tm: &llvm::TargetMachine) {
     let mut llvm_target_features = llvm_target_features(tm);
     let mut known_llvm_target_features = FxHashSet::<&'static str>::default();
     let mut rustc_target_features = supported_target_features(sess)
@@ -383,36 +384,48 @@ fn print_target_features(sess: &Session, tm: &llvm::TargetMachine) {
         .max()
         .unwrap_or(0);
 
-    println!("Features supported by rustc for this target:");
+    writeln!(out, "Features supported by rustc for this target:");
     for (feature, desc) in &rustc_target_features {
-        println!("    {1:0$} - {2}.", max_feature_len, feature, desc);
+        writeln!(out, "    {1:0$} - {2}.", max_feature_len, feature, desc);
     }
-    println!("\nCode-generation features supported by LLVM for this target:");
+    writeln!(out, "\nCode-generation features supported by LLVM for this target:");
     for (feature, desc) in &llvm_target_features {
-        println!("    {1:0$} - {2}.", max_feature_len, feature, desc);
+        writeln!(out, "    {1:0$} - {2}.", max_feature_len, feature, desc);
     }
     if llvm_target_features.is_empty() {
-        println!("    Target features listing is not supported by this LLVM version.");
+        writeln!(out, "    Target features listing is not supported by this LLVM version.");
     }
-    println!("\nUse +feature to enable a feature, or -feature to disable it.");
-    println!("For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
-    println!("Code-generation features cannot be used in cfg or #[target_feature],");
-    println!("and may be renamed or removed in a future version of LLVM or rustc.\n");
+    writeln!(out, "\nUse +feature to enable a feature, or -feature to disable it.");
+    writeln!(out, "For example, rustc -C target-cpu=mycpu -C target-feature=+feature1,-feature2\n");
+    writeln!(out, "Code-generation features cannot be used in cfg or #[target_feature],");
+    writeln!(out, "and may be renamed or removed in a future version of LLVM or rustc.\n");
 }
 
-pub(crate) fn print(req: PrintRequest, sess: &Session) {
+pub(crate) fn print(req: &PrintRequest, mut out: &mut dyn PrintBackendInfo, sess: &Session) {
     require_inited();
     let tm = create_informational_target_machine(sess);
-    match req {
-        PrintRequest::TargetCPUs => {
+    match req.kind {
+        PrintKind::TargetCPUs => {
             // SAFETY generate a C compatible string from a byte slice to pass
             // the target CPU name into LLVM, the lifetime of the reference is
             // at least as long as the C function
             let cpu_cstring = CString::new(handle_native(sess.target.cpu.as_ref()))
                 .unwrap_or_else(|e| bug!("failed to convert to cstring: {}", e));
-            unsafe { llvm::LLVMRustPrintTargetCPUs(tm, cpu_cstring.as_ptr()) };
+            unsafe extern "C" fn callback(out: *mut c_void, string: *const c_char, len: usize) {
+                let out = &mut *(out as *mut &mut dyn PrintBackendInfo);
+                let bytes = slice::from_raw_parts(string as *const u8, len);
+                write!(out, "{}", String::from_utf8_lossy(bytes));
+            }
+            unsafe {
+                llvm::LLVMRustPrintTargetCPUs(
+                    tm,
+                    cpu_cstring.as_ptr(),
+                    callback,
+                    &mut out as *mut &mut dyn PrintBackendInfo as *mut c_void,
+                );
+            }
         }
-        PrintRequest::TargetFeatures => print_target_features(sess, tm),
+        PrintKind::TargetFeatures => print_target_features(out, sess, tm),
         _ => bug!("rustc_codegen_llvm can't handle print request: {:?}", req),
     }
 }

compiler/rustc_codegen_ssa/messages.ftl

@@ -197,6 +197,8 @@ codegen_ssa_specify_libraries_to_link = use the `-l` flag to specify native libr
 
 codegen_ssa_static_library_native_artifacts = Link against the following native artifacts when linking against this static library. The order and any duplication can be significant on some platforms.
 
+codegen_ssa_static_library_native_artifacts_to_file = Native artifacts to link against have been written to {$path}. The order and any duplication can be significant on some platforms.
+
 codegen_ssa_stripping_debug_info_failed = stripping debug info with `{$util}` failed: {$status}
     .note = {$output}
 

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;

compiler/rustc_driver_impl/messages.ftl

@@ -19,5 +19,3 @@ driver_impl_rlink_rustc_version_mismatch = .rlink file was produced by rustc ver
 driver_impl_rlink_unable_to_read = failed to read rlink file: `{$err}`
 
 driver_impl_rlink_wrong_file_type = The input does not look like a .rlink file
-
-driver_impl_unpretty_dump_fail = pretty-print failed to write `{$path}` due to error `{$err}`