Add --dep-info to write Makefile-compatible dependency info.

When --dep-info is given, rustc will write out a `$input_base.d` file in the
output directory that contains Makefile compatible dependency information for
use with tools like make and ninja.

src/librustc/back/link.rs

@@ -720,7 +720,7 @@ pub fn link_binary(sess: Session,
                    trans: &CrateTranslation,
                    obj_filename: &Path,
                    out_filename: &Path,
-                   lm: &LinkMeta) {
+                   lm: &LinkMeta) -> ~[Path] {
     // If we're generating a test executable, then ignore all other output
     // styles at all other locations
     let outputs = if sess.opts.test {
@@ -729,15 +729,19 @@ pub fn link_binary(sess: Session,
         (*sess.outputs).clone()
     };
 
+    let mut out_filenames = ~[];
     for output in outputs.move_iter() {
-        link_binary_output(sess, trans, output, obj_filename, out_filename, lm);
+        let out_file = link_binary_output(sess, trans, output, obj_filename, out_filename, lm);
+        out_filenames.push(out_file);
     }
 
     // Remove the temporary object file and metadata if we aren't saving temps
     if !sess.opts.save_temps {
         fs::unlink(obj_filename);
         fs::unlink(&obj_filename.with_extension("metadata.o"));
     }
+
+    out_filenames
 }
 
 fn is_writeable(p: &Path) -> bool {
@@ -754,7 +758,7 @@ fn link_binary_output(sess: Session,
                       output: session::OutputStyle,
                       obj_filename: &Path,
                       out_filename: &Path,
-                      lm: &LinkMeta) {
+                      lm: &LinkMeta) -> Path {
     let libname = output_lib_filename(lm);
     let out_filename = match output {
         session::OutputRlib => {
@@ -805,6 +809,8 @@ fn link_binary_output(sess: Session,
             link_natively(sess, true, obj_filename, &out_filename);
         }
     }
+
+    out_filename
 }
 
 // Create an 'rlib'

src/librustc/driver/driver.rs

@@ -384,13 +384,34 @@ pub fn phase_5_run_llvm_passes(sess: Session,
 /// This should produce either a finished executable or library.
 pub fn phase_6_link_output(sess: Session,
                            trans: &CrateTranslation,
+                           input: &input,
                            outputs: &OutputFilenames) {
-    time(sess.time_passes(), "linking", (), |_|
+    let outputs = time(sess.time_passes(), "linking", (), |_|
          link::link_binary(sess,
                            trans,
                            &outputs.obj_filename,
                            &outputs.out_filename,
                            &trans.link));
+
+    // Write out dependency rules to the .d file if requested
+    if sess.opts.write_dependency_info {
+        match *input {
+            file_input(ref input_path) => {
+                let files: ~[@str] = sess.codemap.files.iter()
+                    .filter_map(|fmap| if fmap.is_real_file() { Some(fmap.name) } else { None })
+                    .collect();
+                let mut output_path = outputs[0].dir_path();
+                let filestem = input_path.filestem().expect("input file must have stem");
+                output_path.push(Path::new(filestem).with_extension("d"));
+                let mut file = io::File::create(&output_path);
+                for output in outputs.iter() {
+                    write!(&mut file as &mut Writer,
+                           "{}: {}\n\n", output.display(), files.connect(" "));
+                }
+            }
+            str_input(_) => {}
+        }
+    }
 }
 
 pub fn stop_after_phase_3(sess: Session) -> bool {
@@ -438,7 +459,7 @@ pub fn compile_input(sess: Session, cfg: ast::CrateConfig, input: &input,
     };
     phase_5_run_llvm_passes(sess, &trans, outputs);
     if stop_after_phase_5(sess) { return; }
-    phase_6_link_output(sess, &trans, outputs);
+    phase_6_link_output(sess, &trans, input, outputs);
 }
 
 struct IdentifiedAnnotation {
@@ -750,6 +771,7 @@ pub fn build_session_options(binary: @str,
     let cfg = parse_cfgspecs(matches.opt_strs("cfg"), demitter);
     let test = matches.opt_present("test");
     let android_cross_path = matches.opt_str("android-cross-path");
+    let write_dependency_info = matches.opt_present("dep-info");
 
     let custom_passes = match matches.opt_str("passes") {
         None => ~[],
@@ -793,7 +815,8 @@ pub fn build_session_options(binary: @str,
         parse_only: parse_only,
         no_trans: no_trans,
         debugging_opts: debugging_opts,
-        android_cross_path: android_cross_path
+        android_cross_path: android_cross_path,
+        write_dependency_info: write_dependency_info,
     };
     return sopts;
 }
@@ -902,6 +925,8 @@ pub fn optgroups() -> ~[getopts::groups::OptGroup] {
                           or identified (fully parenthesized,
                           AST nodes and blocks with IDs)", "TYPE"),
   optflag("S", "",    "Compile only; do not assemble or link"),
+  optflag("", "dep-info",
+                        "Output dependency info to .d file after compiling"),
   optflag("", "save-temps",
                         "Write intermediate files (.bc, .opt.bc, .o)
                           in addition to normal output"),

src/librustc/driver/session.rs

@@ -170,6 +170,8 @@ pub struct options {
     no_trans: bool,
     debugging_opts: uint,
     android_cross_path: Option<~str>,
+    // Whether to write .d dependency files
+    write_dependency_info: bool,
 }
 
 pub struct crate_metadata {
@@ -393,6 +395,7 @@ pub fn basic_options() -> @options {
         no_trans: false,
         debugging_opts: 0u,
         android_cross_path: None,
+        write_dependency_info: false,
     }
 }
 

src/librustpkg/util.rs

@@ -353,7 +353,8 @@ pub fn compile_crate_from_input(input: &Path,
 
     // bad copy
     debug!("out_dir = {}", out_dir.display());
-    let mut outputs = driver::build_output_filenames(&driver::file_input(input.clone()),
+    let file_input = driver::file_input(input.clone());
+    let mut outputs = driver::build_output_filenames(&file_input,
                                                      &Some(out_dir.clone()), &None,
                                                      crate.attrs, sess);
     match what {
@@ -388,7 +389,7 @@ pub fn compile_crate_from_input(input: &Path,
     // -c
     if driver::stop_after_phase_5(sess)
         || stop_before == Link || stop_before == Assemble { return Some(outputs.out_filename); }
-    driver::phase_6_link_output(sess, &translation, outputs);
+    driver::phase_6_link_output(sess, &translation, &file_input, outputs);
 
     // Register dependency on the source file
     // FIXME (#9639): This needs to handle non-utf8 paths

src/libsyntax/codemap.rs

@@ -260,6 +260,10 @@ impl FileMap {
         };
         self.multibyte_chars.push(mbc);
     }
+
+    pub fn is_real_file(&self) -> bool {
+        !(self.name.starts_with("<") && self.name.ends_with(">"))
+    }
 }
 
 pub struct CodeMap {