output target json files

src/librustc/session/config.rs

@@ -164,6 +164,7 @@ pub enum PrintRequest {
     CrateName,
     Cfg,
     TargetList,
+    TargetSpec,
 }
 
 pub enum Input {
@@ -905,7 +906,7 @@ pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
                  "[asm|llvm-bc|llvm-ir|obj|link|dep-info]"),
         opt::multi_s("", "print", "Comma separated list of compiler information to \
                                print on stdout",
-                 "[crate-name|file-names|sysroot|cfg|target-list]"),
+                 "[crate-name|file-names|sysroot|cfg|target-list|target-spec]"),
         opt::flagmulti_s("g",  "",  "Equivalent to -C debuginfo=2"),
         opt::flagmulti_s("O", "", "Equivalent to -C opt-level=2"),
         opt::opt_s("o", "", "Write output to <filename>", "FILENAME"),
@@ -1189,6 +1190,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
             "sysroot" => PrintRequest::Sysroot,
             "cfg" => PrintRequest::Cfg,
             "target-list" => PrintRequest::TargetList,
+            "target-spec" => PrintRequest::TargetSpec,
             req => {
                 early_error(error_format, &format!("unknown print request `{}`", req))
             }

src/librustc_back/target/mod.rs

@@ -45,7 +45,8 @@
 //! settings, though `target-feature` and `link-args` will *add* to the list
 //! specified by the target, rather than replace.
 
-use serialize::json::Json;
+use serialize::json::{Json, ToJson};
+use std::collections::BTreeMap;
 use std::default::Default;
 use std::io::prelude::*;
 use syntax::abi::Abi;
@@ -504,6 +505,80 @@ impl Target {
     }
 }
 
+impl ToJson for Target {
+    fn to_json(&self) -> Json {
+        let mut d = BTreeMap::new();
+        let default: TargetOptions = Default::default();
+
+        macro_rules! target_val {
+            ($attr:ident) => ( {
+                let name = (stringify!($attr)).replace("_", "-");
+                d.insert(name.to_string(), self.$attr.to_json());
+            } );
+            ($attr:ident, $key_name:expr) => ( {
+                let name = $key_name;
+                d.insert(name.to_string(), self.$attr.to_json());
+            } );
+        }
+
+        macro_rules! target_option_val {
+            ($attr:ident) => ( {
+                let name = (stringify!($attr)).replace("_", "-");
+                if default.$attr != self.options.$attr {
+                    d.insert(name.to_string(), self.options.$attr.to_json());
+                }
+            } );
+            ($attr:ident, $key_name:expr) => ( {
+                let name = $key_name;
+                if default.$attr != self.options.$attr {
+                    d.insert(name.to_string(), self.options.$attr.to_json());
+                }
+            } );
+        }
+
+        target_val!(llvm_target);
+        target_val!(target_endian);
+        target_val!(target_pointer_width);
+        target_val!(arch);
+        target_val!(target_os, "os");
+        target_val!(target_env, "env");
+        target_val!(target_vendor, "vendor");
+
+        target_option_val!(cpu);
+        target_option_val!(ar);
+        target_option_val!(linker);
+        target_option_val!(relocation_model);
+        target_option_val!(code_model);
+        target_option_val!(dll_prefix);
+        target_option_val!(dll_suffix);
+        target_option_val!(exe_suffix);
+        target_option_val!(staticlib_prefix);
+        target_option_val!(staticlib_suffix);
+        target_option_val!(features);
+        target_option_val!(data_layout);
+        target_option_val!(dynamic_linking);
+        target_option_val!(executables);
+        target_option_val!(disable_redzone);
+        target_option_val!(eliminate_frame_pointer);
+        target_option_val!(function_sections);
+        target_option_val!(target_family);
+        target_option_val!(is_like_osx);
+        target_option_val!(is_like_windows);
+        target_option_val!(is_like_msvc);
+        target_option_val!(linker_is_gnu);
+        target_option_val!(has_rpath);
+        target_option_val!(no_compiler_rt);
+        target_option_val!(no_default_libraries);
+        target_option_val!(pre_link_args);
+        target_option_val!(post_link_args);
+        target_option_val!(archive_format);
+        target_option_val!(allow_asm);
+        target_option_val!(custom_unwind_resume);
+
+        Json::Object(d)
+    }
+}
+
 fn maybe_jemalloc() -> String {
     if cfg!(feature = "jemalloc") {
         "alloc_jemalloc".to_string()

src/librustc_driver/lib.rs

@@ -76,6 +76,8 @@ use rustc_metadata::loader;
 use rustc_metadata::cstore::CStore;
 use rustc::util::common::time;
 
+use serialize::json::ToJson;
+
 use std::cmp::max;
 use std::cmp::Ordering::Equal;
 use std::default::Default;
@@ -560,6 +562,7 @@ impl RustcDefaultCalls {
                     println!("{}", targets.join("\n"));
                 },
                 PrintRequest::Sysroot => println!("{}", sess.sysroot().display()),
+                PrintRequest::TargetSpec => println!("{}", sess.target.target.to_json().pretty()),
                 PrintRequest::FileNames |
                 PrintRequest::CrateName => {
                     let input = match input {

src/test/run-make/target-specs/Makefile

@@ -6,3 +6,4 @@ all:
 	$(RUSTC) foo.rs --target=my-incomplete-platform.json 2>&1 | grep 'Field llvm-target'
 	RUST_TARGET_PATH=. $(RUSTC) foo.rs --target=my-awesome-platform --crate-type=lib --emit=asm
 	RUST_TARGET_PATH=. $(RUSTC) foo.rs --target=x86_64-unknown-linux-gnu --crate-type=lib --emit=asm
+	$(RUSTC) --target=my-awesome-platform.json --print target-spec > $(TMPDIR)/test-platform.json && $(RUSTC) --target=$(TMPDIR)/test-platform.json --print target-spec | diff -q $(TMPDIR)/test-platform.json -