Implement printing to file in codegen_backend.print

compiler/rustc_codegen_llvm/src/lib.rs

@@ -262,10 +262,10 @@ impl CodegenBackend for LlvmCodegenBackend {
             |tcx, ()| llvm_util::global_llvm_features(tcx.sess, true)
     }
 
-    fn print(&self, req: &PrintRequest, sess: &Session) {
+    fn print(&self, req: &PrintRequest, out: &mut dyn PrintBackendInfo, sess: &Session) {
         match req.kind {
             PrintKind::RelocationModels => {
-                println!("Available relocation models:");
+                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);
             }
             PrintKind::CodeModels => {
-                println!("Available code models:");
+                writeln!(out, "Available code models:");
                 for name in &["tiny", "small", "kernel", "medium", "large"] {
-                    println!("    {}", name);
+                    writeln!(out, "    {}", name);
                 }
-                println!();
+                writeln!(out);
             }
             PrintKind::TlsModels => {
-                println!("Available TLS models:");
+                writeln!(out, "Available TLS models:");
                 for name in &["global-dynamic", "local-dynamic", "initial-exec", "local-exec"] {
-                    println!("    {}", name);
+                    writeln!(out, "    {}", name);
                 }
-                println!();
+                writeln!(out);
             }
             PrintKind::StackProtectorStrategies => {
-                println!(
+                writeln!(
+                    out,
                     r#"Available stack protector strategies:
     all
         Generate stack canaries in all functions.

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 +30,7 @@ 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/src/lib.rs

@@ -834,7 +834,7 @@ fn print_crate_info(
             | TargetCPUs
             | StackProtectorStrategies
             | TargetFeatures => {
-                codegen_backend.print(req, sess);
+                codegen_backend.print(req, &mut crate_info, sess);
             }
             // Any output here interferes with Cargo's parsing of other printed output
             NativeStaticLibs => {}