rustc: Add target_env for triples by default

This adds a new `#[cfg]` matcher against the `target_env` property of the
destination target triple. For example all windows triples today end with `-gnu`
but we will also hopefully support non-`gnu` targets for Windows, at which point
we'll need to differentiate between the two. This new `target_env` matches is
provided and filled in with the target's environment name.

Currently the only non-empty value of this name is `gnu`, but `musl` will be
shortly added for the linux triples.

src/librustc/session/config.rs

@@ -621,6 +621,7 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig {
     let arch = &sess.target.target.arch;
     let wordsz = &sess.target.target.target_pointer_width;
     let os = &sess.target.target.target_os;
+    let env = &sess.target.target.target_env;
 
     let fam = match sess.target.target.options.is_like_windows {
         true  => InternedString::new("windows"),
@@ -634,8 +635,8 @@ pub fn default_configuration(sess: &Session) -> ast::CrateConfig {
          mk(InternedString::new("target_family"), fam),
          mk(InternedString::new("target_arch"), intern(arch)),
          mk(InternedString::new("target_endian"), intern(end)),
-         mk(InternedString::new("target_pointer_width"),
-            intern(wordsz))
+         mk(InternedString::new("target_pointer_width"), intern(wordsz)),
+         mk(InternedString::new("target_env"), intern(env)),
     ];
     if sess.opts.debug_assertions {
         ret.push(attr::mk_word_item(InternedString::new("debug_assertions")));

src/librustc_back/target/aarch64_apple_ios.rs

@@ -22,6 +22,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "aarch64".to_string(),
         target_os: "ios".to_string(),
+        target_env: "".to_string(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+cyclone".to_string(),
             eliminate_frame_pointer: false,

src/librustc_back/target/aarch64_linux_android.rs

@@ -24,6 +24,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "aarch64".to_string(),
         target_os: "android".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }

src/librustc_back/target/aarch64_unknown_linux_gnu.rs

@@ -19,6 +19,7 @@ pub fn target() -> Target {
         llvm_target: "aarch64-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),
+        target_env: "gnu".to_string(),
         arch: "aarch64".to_string(),
         target_os: "linux".to_string(),
         options: base,

src/librustc_back/target/arm_linux_androideabi.rs

@@ -31,6 +31,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "arm".to_string(),
         target_os: "android".to_string(),
+        target_env: "gnu".to_string(),
         options: base,
     }
 }

src/librustc_back/target/arm_unknown_linux_gnueabi.rs

@@ -23,6 +23,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "arm".to_string(),
         target_os: "linux".to_string(),
+        target_env: "gnueabi".to_string(),
 
         options: TargetOptions {
             features: "+v6".to_string(),

src/librustc_back/target/arm_unknown_linux_gnueabihf.rs

@@ -23,6 +23,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "arm".to_string(),
         target_os: "linux".to_string(),
+        target_env: "gnueabihf".to_string(),
 
         options: TargetOptions {
             features: "+v6,+vfp2".to_string(),

src/librustc_back/target/armv7_apple_ios.rs

@@ -19,6 +19,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "arm".to_string(),
         target_os: "ios".to_string(),
+        target_env: "".to_string(),
         options: TargetOptions {
             features: "+v7,+vfp3,+neon".to_string(),
             .. opts(Arch::Armv7)

src/librustc_back/target/armv7s_apple_ios.rs

@@ -19,6 +19,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "arm".to_string(),
         target_os: "ios".to_string(),
+        target_env: "".to_string(),
         options: TargetOptions {
             features: "+v7,+vfp4,+neon".to_string(),
             .. opts(Arch::Armv7s)

src/librustc_back/target/i386_apple_ios.rs

@@ -23,6 +23,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "x86".to_string(),
         target_os: "ios".to_string(),
+        target_env: "".to_string(),
         options: opts(Arch::I386)
     }
 }

src/librustc_back/target/i686_apple_darwin.rs

@@ -26,6 +26,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "x86".to_string(),
         target_os: "macos".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }

src/librustc_back/target/i686_pc_windows_gnu.rs

@@ -30,6 +30,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "x86".to_string(),
         target_os: "windows".to_string(),
+        target_env: "gnu".to_string(),
         options: options,
     }
 }

src/librustc_back/target/i686_unknown_dragonfly.rs

@@ -22,6 +22,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "x86".to_string(),
         target_os: "dragonfly".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }

src/librustc_back/target/i686_unknown_linux_gnu.rs

@@ -22,6 +22,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "x86".to_string(),
         target_os: "linux".to_string(),
+        target_env: "gnu".to_string(),
         options: base,
     }
 }

src/librustc_back/target/mips_unknown_linux_gnu.rs

@@ -22,6 +22,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "mips".to_string(),
         target_os: "linux".to_string(),
+        target_env: "gnu".to_string(),
         options: super::linux_base::opts()
     }
 }

src/librustc_back/target/mipsel_unknown_linux_gnu.rs

@@ -22,6 +22,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "mips".to_string(),
         target_os: "linux".to_string(),
+        target_env: "gnu".to_string(),
 
         options: super::linux_base::opts()
     }

src/librustc_back/target/mod.rs

@@ -100,6 +100,8 @@ pub struct Target {
     pub target_pointer_width: String,
     /// OS name to use for conditional compilation.
     pub target_os: String,
+    /// Environment name to use for conditional compilation.
+    pub target_env: String,
     /// Architecture to use for ABI considerations. Valid options: "x86", "x86_64", "arm",
     /// "aarch64", "mips", and "powerpc". "mips" includes "mipsel".
     pub arch: String,
@@ -250,6 +252,8 @@ impl Target {
             target_pointer_width: get_req_field("target-pointer-width"),
             arch: get_req_field("arch"),
             target_os: get_req_field("os"),
+            target_env: obj.find("env").and_then(|s| s.as_string())
+                           .map(|s| s.to_string()).unwrap_or(String::new()),
             options: Default::default(),
         };
 

src/librustc_back/target/powerpc_unknown_linux_gnu.rs

@@ -21,6 +21,7 @@ pub fn target() -> Target {
         target_pointer_width: "32".to_string(),
         arch: "powerpc".to_string(),
         target_os: "linux".to_string(),
+        target_env: "gnu".to_string(),
         options: base,
     }
 }

src/librustc_back/target/x86_64_apple_darwin.rs

@@ -25,6 +25,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "macos".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }

src/librustc_back/target/x86_64_apple_ios.rs

@@ -21,6 +21,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "ios".to_string(),
+        target_env: "".to_string(),
         options: opts(Arch::X86_64)
     }
 }

src/librustc_back/target/x86_64_pc_windows_gnu.rs

@@ -27,6 +27,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "windows".to_string(),
+        target_env: "gnu".to_string(),
         options: base,
     }
 }

src/librustc_back/target/x86_64_unknown_bitrig.rs

@@ -23,6 +23,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "bitrig".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }

src/librustc_back/target/x86_64_unknown_dragonfly.rs

@@ -24,6 +24,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "dragonfly".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }

src/librustc_back/target/x86_64_unknown_freebsd.rs

@@ -24,6 +24,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "freebsd".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }

src/librustc_back/target/x86_64_unknown_linux_gnu.rs

@@ -24,6 +24,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "linux".to_string(),
+        target_env: "gnu".to_string(),
         options: base,
     }
 }

src/librustc_back/target/x86_64_unknown_openbsd.rs

@@ -23,6 +23,7 @@ pub fn target() -> Target {
         target_pointer_width: "64".to_string(),
         arch: "x86_64".to_string(),
         target_os: "openbsd".to_string(),
+        target_env: "".to_string(),
         options: base,
     }
 }