librustc_back: filter targets for only valid ones

Since we can know which targets are instantiable on a particular host,
it does not make sense to list invalid targets in the target print code.
Filter the list of targets to only include the targets that can be
instantiated.

2 files changed, 10 insertions, 2 deletions

diff --git a/src/librustc_back/target/mod.rs b/src/librustc_back/target/mod.rs
index 84cb6c9ba7d..f5314809228 100644
--- a/src/librustc_back/target/mod.rs
+++ b/src/librustc_back/target/mod.rs
@@ -71,7 +71,7 @@ macro_rules! supported_targets {
         $(mod $module;)*
 
         /// List of supported targets
-        pub const TARGETS: &'static [&'static str] = &[$($triple),*];
+        const TARGETS: &'static [&'static str] = &[$($triple),*];
 
         fn load_specific(target: &str) -> TargetResult {
             match target {
@@ -91,6 +91,14 @@ macro_rules! supported_targets {
             }
         }
 
+        pub fn get_targets() -> Box<Iterator<Item=String>> {
+            Box::new(TARGETS.iter().filter_map(|t| -> Option<String> {
+                load_specific(t)
+                    .map(|t| t.llvm_target)
+                    .ok()
+            }))
+        }
+
         #[cfg(test)]
         mod test_json_encode_decode {
             use serialize::json::ToJson;
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 0a8df923b84..eff920608dc 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -609,7 +609,7 @@ impl RustcDefaultCalls {
         for req in &sess.opts.prints {
             match *req {
                 PrintRequest::TargetList => {
-                    let mut targets = rustc_back::target::TARGETS.to_vec();
+                    let mut targets = rustc_back::target::get_targets().collect::<Vec<String>>();
                     targets.sort();
                     println!("{}", targets.join("\n"));
                 },