auto merge of #10367 : alexcrichton/rust/system-abi, r=nikomatsakis

This adds an other ABI option which allows a custom selection over the target
architecture and OS. The only current candidate for this change is that kernel32
on win32 uses stdcall, but on win64 it uses the cdecl calling convention.
Otherwise everywhere else this is defined as using the Cdecl calling convention.

cc #10049
Closes #8774

13 files changed, 131 insertions, 106 deletions

diff --git a/src/librustc/back/arm.rs b/src/librustc/back/arm.rs
index 42855b63ff8..a3ac468a5f0 100644
--- a/src/librustc/back/arm.rs
+++ b/src/librustc/back/arm.rs
@@ -10,17 +10,17 @@
 
 use back::target_strs;
 use driver::session::sess_os_to_meta_os;
-use driver::session;
 use metadata::loader::meta_section_name;
+use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_strs::t {
+pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
     return target_strs::t {
         module_asm: ~"",
 
         meta_sect_name: meta_section_name(sess_os_to_meta_os(target_os)).to_owned(),
 
         data_layout: match target_os {
-          session::OsMacos => {
+          abi::OsMacos => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -28,7 +28,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsWin32 => {
+          abi::OsWin32 => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -36,7 +36,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsLinux => {
+          abi::OsLinux => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -44,7 +44,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsAndroid => {
+          abi::OsAndroid => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -52,7 +52,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsFreebsd => {
+          abi::OsFreebsd => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
diff --git a/src/librustc/back/link.rs b/src/librustc/back/link.rs
index b88966c0ab2..21268c132ba 100644
--- a/src/librustc/back/link.rs
+++ b/src/librustc/back/link.rs
@@ -32,6 +32,7 @@ use std::run;
 use std::str;
 use std::vec;
 use std::rt::io::fs;
+use syntax::abi;
 use syntax::ast;
 use syntax::ast_map::{path, path_mod, path_name, path_pretty_name};
 use syntax::attr;
@@ -877,13 +878,13 @@ pub fn mangle_internal_name_by_path(ccx: &mut CrateContext, path: path) -> ~str
 }
 
 
-pub fn output_dll_filename(os: session::Os, lm: LinkMeta) -> ~str {
+pub fn output_dll_filename(os: abi::Os, lm: LinkMeta) -> ~str {
     let (dll_prefix, dll_suffix) = match os {
-        session::OsWin32 => (win32::DLL_PREFIX, win32::DLL_SUFFIX),
-        session::OsMacos => (macos::DLL_PREFIX, macos::DLL_SUFFIX),
-        session::OsLinux => (linux::DLL_PREFIX, linux::DLL_SUFFIX),
-        session::OsAndroid => (android::DLL_PREFIX, android::DLL_SUFFIX),
-        session::OsFreebsd => (freebsd::DLL_PREFIX, freebsd::DLL_SUFFIX),
+        abi::OsWin32 => (win32::DLL_PREFIX, win32::DLL_SUFFIX),
+        abi::OsMacos => (macos::DLL_PREFIX, macos::DLL_SUFFIX),
+        abi::OsLinux => (linux::DLL_PREFIX, linux::DLL_SUFFIX),
+        abi::OsAndroid => (android::DLL_PREFIX, android::DLL_SUFFIX),
+        abi::OsFreebsd => (freebsd::DLL_PREFIX, freebsd::DLL_SUFFIX),
     };
     format!("{}{}-{}-{}{}", dll_prefix, lm.name, lm.extras_hash, lm.vers, dll_suffix)
 }
@@ -898,7 +899,7 @@ pub fn get_cc_prog(sess: Session) -> ~str {
     match sess.opts.linker {
         Some(ref linker) => linker.to_str(),
         None => match sess.targ_cfg.os {
-            session::OsAndroid =>
+            abi::OsAndroid =>
                 match &sess.opts.android_cross_path {
                     &Some(ref path) => {
                         format!("{}/bin/arm-linux-androideabi-gcc", *path)
@@ -908,7 +909,7 @@ pub fn get_cc_prog(sess: Session) -> ~str {
                                     (--android-cross-path)")
                     }
                 },
-            session::OsWin32 => ~"g++",
+            abi::OsWin32 => ~"g++",
             _ => ~"cc"
         }
     }
@@ -956,7 +957,7 @@ pub fn link_binary(sess: Session,
     }
 
     // Clean up on Darwin
-    if sess.targ_cfg.os == session::OsMacos {
+    if sess.targ_cfg.os == abi::OsMacos {
         // FIXME (#9639): This needs to handle non-utf8 paths
         run::process_status("dsymutil", [output.as_str().unwrap().to_owned()]);
     }
@@ -985,7 +986,7 @@ pub fn link_args(sess: Session,
     // Converts a library file-stem into a cc -l argument
     fn unlib(config: @session::config, stem: ~str) -> ~str {
         if stem.starts_with("lib") &&
-            config.os != session::OsWin32 {
+            config.os != abi::OsWin32 {
             stem.slice(3, stem.len()).to_owned()
         } else {
             stem
@@ -1029,7 +1030,7 @@ pub fn link_args(sess: Session,
         obj_filename.as_str().unwrap().to_owned()]);
 
     let lib_cmd = match sess.targ_cfg.os {
-        session::OsMacos => ~"-dynamiclib",
+        abi::OsMacos => ~"-dynamiclib",
         _ => ~"-shared"
     };
 
@@ -1080,7 +1081,7 @@ pub fn link_args(sess: Session,
 
         // On mac we need to tell the linker to let this library
         // be rpathed
-        if sess.targ_cfg.os == session::OsMacos {
+        if sess.targ_cfg.os == abi::OsMacos {
             // FIXME (#9639): This needs to handle non-utf8 paths
             args.push("-Wl,-install_name,@rpath/"
                       + output.filename_str().unwrap());
@@ -1089,7 +1090,7 @@ pub fn link_args(sess: Session,
 
     // On linux librt and libdl are an indirect dependencies via rustrt,
     // and binutils 2.22+ won't add them automatically
-    if sess.targ_cfg.os == session::OsLinux {
+    if sess.targ_cfg.os == abi::OsLinux {
         args.push_all([~"-lrt", ~"-ldl"]);
 
         // LLVM implements the `frem` instruction as a call to `fmod`,
@@ -1097,12 +1098,12 @@ pub fn link_args(sess: Session,
         // have to be explicit about linking to it. See #2510
         args.push(~"-lm");
     }
-    else if sess.targ_cfg.os == session::OsAndroid {
+    else if sess.targ_cfg.os == abi::OsAndroid {
         args.push_all([~"-ldl", ~"-llog",  ~"-lsupc++", ~"-lgnustl_shared"]);
         args.push(~"-lm");
     }
 
-    if sess.targ_cfg.os == session::OsFreebsd {
+    if sess.targ_cfg.os == abi::OsFreebsd {
         args.push_all([~"-pthread", ~"-lrt",
                        ~"-L/usr/local/lib", ~"-lexecinfo",
                        ~"-L/usr/local/lib/gcc46",
diff --git a/src/librustc/back/mips.rs b/src/librustc/back/mips.rs
index 52d8463adfe..cbe39efdf8c 100644
--- a/src/librustc/back/mips.rs
+++ b/src/librustc/back/mips.rs
@@ -9,18 +9,18 @@
 // except according to those terms.
 
 use back::target_strs;
-use driver::session;
 use driver::session::sess_os_to_meta_os;
 use metadata::loader::meta_section_name;
+use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_strs::t {
+pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
     return target_strs::t {
         module_asm: ~"",
 
         meta_sect_name: meta_section_name(sess_os_to_meta_os(target_os)).to_owned(),
 
         data_layout: match target_os {
-          session::OsMacos => {
+          abi::OsMacos => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -28,7 +28,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsWin32 => {
+          abi::OsWin32 => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -36,7 +36,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsLinux => {
+          abi::OsLinux => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -44,7 +44,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsAndroid => {
+          abi::OsAndroid => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
@@ -52,7 +52,7 @@ pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_st
                 "-a0:0:64-n32"
           }
 
-          session::OsFreebsd => {
+          abi::OsFreebsd => {
             ~"e-p:32:32:32" +
                 "-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64" +
                 "-f32:32:32-f64:64:64" +
diff --git a/src/librustc/back/rpath.rs b/src/librustc/back/rpath.rs
index 6f76b228d3e..5e6a5080dce 100644
--- a/src/librustc/back/rpath.rs
+++ b/src/librustc/back/rpath.rs
@@ -15,9 +15,10 @@ use metadata::filesearch;
 
 use std::hashmap::HashSet;
 use std::{os, vec};
+use syntax::abi;
 
-fn not_win32(os: session::Os) -> bool {
-  os != session::OsWin32
+fn not_win32(os: abi::Os) -> bool {
+  os != abi::OsWin32
 }
 
 pub fn get_rpath_flags(sess: session::Session, out_filename: &Path)
@@ -25,7 +26,7 @@ pub fn get_rpath_flags(sess: session::Session, out_filename: &Path)
     let os = sess.targ_cfg.os;
 
     // No rpath on windows
-    if os == session::OsWin32 {
+    if os == abi::OsWin32 {
         return ~[];
     }
 
@@ -55,7 +56,7 @@ pub fn rpaths_to_flags(rpaths: &[~str]) -> ~[~str] {
     rpaths.iter().map(|rpath| format!("-Wl,-rpath,{}",*rpath)).collect()
 }
 
-fn get_rpaths(os: session::Os,
+fn get_rpaths(os: abi::Os,
               sysroot: &Path,
               output: &Path,
               libs: &[Path],
@@ -100,13 +101,13 @@ fn get_rpaths(os: session::Os,
     return rpaths;
 }
 
-fn get_rpaths_relative_to_output(os: session::Os,
+fn get_rpaths_relative_to_output(os: abi::Os,
                                  output: &Path,
                                  libs: &[Path]) -> ~[~str] {
     libs.iter().map(|a| get_rpath_relative_to_output(os, output, a)).collect()
 }
 
-pub fn get_rpath_relative_to_output(os: session::Os,
+pub fn get_rpath_relative_to_output(os: abi::Os,
                                     output: &Path,
                                     lib: &Path)
                                  -> ~str {
@@ -116,10 +117,10 @@ pub fn get_rpath_relative_to_output(os: session::Os,
 
     // Mac doesn't appear to support $ORIGIN
     let prefix = match os {
-        session::OsAndroid | session::OsLinux | session::OsFreebsd
+        abi::OsAndroid | abi::OsLinux | abi::OsFreebsd
                           => "$ORIGIN",
-        session::OsMacos => "@loader_path",
-        session::OsWin32 => unreachable!()
+        abi::OsMacos => "@loader_path",
+        abi::OsWin32 => unreachable!()
     };
 
     let mut lib = os::make_absolute(lib);
@@ -169,13 +170,10 @@ pub fn minimize_rpaths(rpaths: &[~str]) -> ~[~str] {
 mod test {
     use std::os;
 
-    // FIXME(#2119): the outer attribute should be #[cfg(unix, test)], then
-    // these redundant #[cfg(test)] blocks can be removed
-    #[cfg(test)]
-    #[cfg(test)]
     use back::rpath::{get_absolute_rpath, get_install_prefix_rpath};
     use back::rpath::{minimize_rpaths, rpaths_to_flags, get_rpath_relative_to_output};
     use driver::session;
+    use syntax::abi;
 
     #[test]
     fn test_rpaths_to_flags() {
@@ -219,7 +217,7 @@ mod test {
     #[cfg(target_os = "linux")]
     #[cfg(target_os = "android")]
     fn test_rpath_relative() {
-      let o = session::OsLinux;
+      let o = abi::OsLinux;
       let res = get_rpath_relative_to_output(o,
             &Path::new("bin/rustc"), &Path::new("lib/libstd.so"));
       assert_eq!(res.as_slice(), "$ORIGIN/../lib");
@@ -228,7 +226,7 @@ mod test {
     #[test]
     #[cfg(target_os = "freebsd")]
     fn test_rpath_relative() {
-        let o = session::OsFreebsd;
+        let o = abi::OsFreebsd;
         let res = get_rpath_relative_to_output(o,
             &Path::new("bin/rustc"), &Path::new("lib/libstd.so"));
         assert_eq!(res.as_slice(), "$ORIGIN/../lib");
@@ -237,7 +235,7 @@ mod test {
     #[test]
     #[cfg(target_os = "macos")]
     fn test_rpath_relative() {
-        let o = session::OsMacos;
+        let o = abi::OsMacos;
         let res = get_rpath_relative_to_output(o,
                                                &Path::new("bin/rustc"),
                                                &Path::new("lib/libstd.so"));
diff --git a/src/librustc/back/x86.rs b/src/librustc/back/x86.rs
index 4518ec0a148..b3c92bc4057 100644
--- a/src/librustc/back/x86.rs
+++ b/src/librustc/back/x86.rs
@@ -11,35 +11,35 @@
 
 use back::target_strs;
 use driver::session::sess_os_to_meta_os;
-use driver::session;
 use metadata::loader::meta_section_name;
+use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_strs::t {
+pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
     return target_strs::t {
         module_asm: ~"",
 
         meta_sect_name: meta_section_name(sess_os_to_meta_os(target_os)).to_owned(),
 
         data_layout: match target_os {
-          session::OsMacos => {
+          abi::OsMacos => {
             ~"e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16" +
                 "-i32:32:32-i64:32:64" +
                 "-f32:32:32-f64:32:64-v64:64:64" +
                 "-v128:128:128-a0:0:64-f80:128:128" + "-n8:16:32"
           }
 
-          session::OsWin32 => {
+          abi::OsWin32 => {
             ~"e-p:32:32-f64:64:64-i64:64:64-f80:32:32-n8:16:32"
           }
 
-          session::OsLinux => {
+          abi::OsLinux => {
             ~"e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32"
           }
-          session::OsAndroid => {
+          abi::OsAndroid => {
             ~"e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32"
           }
 
-          session::OsFreebsd => {
+          abi::OsFreebsd => {
             ~"e-p:32:32-f64:32:64-i64:32:64-f80:32:32-n8:16:32"
           }
         },
diff --git a/src/librustc/back/x86_64.rs b/src/librustc/back/x86_64.rs
index 3833f0d2b94..3237085dfb9 100644
--- a/src/librustc/back/x86_64.rs
+++ b/src/librustc/back/x86_64.rs
@@ -11,41 +11,41 @@
 
 use back::target_strs;
 use driver::session::sess_os_to_meta_os;
-use driver::session;
 use metadata::loader::meta_section_name;
+use syntax::abi;
 
-pub fn get_target_strs(target_triple: ~str, target_os: session::Os) -> target_strs::t {
+pub fn get_target_strs(target_triple: ~str, target_os: abi::Os) -> target_strs::t {
     return target_strs::t {
         module_asm: ~"",
 
         meta_sect_name: meta_section_name(sess_os_to_meta_os(target_os)).to_owned(),
 
         data_layout: match target_os {
-          session::OsMacos => {
+          abi::OsMacos => {
             ~"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-"+
                 "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
                 "s0:64:64-f80:128:128-n8:16:32:64"
           }
 
-          session::OsWin32 => {
+          abi::OsWin32 => {
             // FIXME: Test this. Copied from linux (#2398)
             ~"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-"+
                 "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
                 "s0:64:64-f80:128:128-n8:16:32:64-S128"
           }
 
-          session::OsLinux => {
+          abi::OsLinux => {
             ~"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-"+
                 "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
                 "s0:64:64-f80:128:128-n8:16:32:64-S128"
           }
-          session::OsAndroid => {
+          abi::OsAndroid => {
             ~"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-"+
                 "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
                 "s0:64:64-f80:128:128-n8:16:32:64-S128"
           }
 
-          session::OsFreebsd => {
+          abi::OsFreebsd => {
             ~"e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-"+
                 "f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-"+
                 "s0:64:64-f80:128:128-n8:16:32:64-S128"
diff --git a/src/librustc/driver/driver.rs b/src/librustc/driver/driver.rs
index 6346e4856f2..34c03ac8e42 100644
--- a/src/librustc/driver/driver.rs
+++ b/src/librustc/driver/driver.rs
@@ -69,11 +69,11 @@ pub fn source_name(input: &input) -> @str {
 pub fn default_configuration(sess: Session) ->
    ast::CrateConfig {
     let tos = match sess.targ_cfg.os {
-        session::OsWin32 =>   @"win32",
-        session::OsMacos =>   @"macos",
-        session::OsLinux =>   @"linux",
-        session::OsAndroid => @"android",
-        session::OsFreebsd => @"freebsd"
+        abi::OsWin32 =>   @"win32",
+        abi::OsMacos =>   @"macos",
+        abi::OsLinux =>   @"linux",
+        abi::OsAndroid => @"android",
+        abi::OsFreebsd => @"freebsd"
     };
 
     // ARM is bi-endian, however using NDK seems to default
@@ -353,7 +353,7 @@ pub fn phase_5_run_llvm_passes(sess: Session,
     // segmented stacks are enabled.  However, unwind info directives in assembly
     // output are OK, so we generate assembly first and then run it through
     // an external assembler.
-    if sess.targ_cfg.os == session::OsWin32 &&
+    if sess.targ_cfg.os == abi::OsWin32 &&
         (sess.opts.output_type == link::output_type_object ||
          sess.opts.output_type == link::output_type_exe) {
         let output_type = link::output_type_assembly;
@@ -567,19 +567,19 @@ pub fn pretty_print_input(sess: Session,
                         is_expanded);
 }
 
-pub fn get_os(triple: &str) -> Option<session::Os> {
+pub fn get_os(triple: &str) -> Option<abi::Os> {
     for &(name, os) in os_names.iter() {
         if triple.contains(name) { return Some(os) }
     }
     None
 }
-static os_names : &'static [(&'static str, session::Os)] = &'static [
-    ("mingw32", session::OsWin32),
-    ("win32",   session::OsWin32),
-    ("darwin",  session::OsMacos),
-    ("android", session::OsAndroid),
-    ("linux",   session::OsLinux),
-    ("freebsd", session::OsFreebsd)];
+static os_names : &'static [(&'static str, abi::Os)] = &'static [
+    ("mingw32", abi::OsWin32),
+    ("win32",   abi::OsWin32),
+    ("darwin",  abi::OsMacos),
+    ("android", abi::OsAndroid),
+    ("linux",   abi::OsLinux),
+    ("freebsd", abi::OsFreebsd)];
 
 pub fn get_arch(triple: &str) -> Option<abi::Architecture> {
     for &(arch, abi) in architecture_abis.iter() {
diff --git a/src/librustc/driver/session.rs b/src/librustc/driver/session.rs
index 8c1693935c7..57edb355d32 100644
--- a/src/librustc/driver/session.rs
+++ b/src/librustc/driver/session.rs
@@ -31,9 +31,6 @@ use syntax;
 use std::int;
 use std::hashmap::{HashMap,HashSet};
 
-#[deriving(Eq)]
-pub enum Os { OsWin32, OsMacos, OsLinux, OsAndroid, OsFreebsd, }
-
 #[deriving(Clone)]
 pub enum crate_type {
     bin_crate,
@@ -42,7 +39,7 @@ pub enum crate_type {
 }
 
 pub struct config {
-    os: Os,
+    os: abi::Os,
     arch: abi::Architecture,
     target_strs: target_strs::t,
     int_type: int_ty,
@@ -410,15 +407,15 @@ pub fn building_library(req_crate_type: crate_type,
     }
 }
 
-pub fn sess_os_to_meta_os(os: Os) -> metadata::loader::Os {
+pub fn sess_os_to_meta_os(os: abi::Os) -> metadata::loader::Os {
     use metadata::loader;
 
     match os {
-        OsWin32 => loader::OsWin32,
-        OsLinux => loader::OsLinux,
-        OsAndroid => loader::OsAndroid,
-        OsMacos => loader::OsMacos,
-        OsFreebsd => loader::OsFreebsd
+        abi::OsWin32 => loader::OsWin32,
+        abi::OsLinux => loader::OsLinux,
+        abi::OsAndroid => loader::OsAndroid,
+        abi::OsMacos => loader::OsMacos,
+        abi::OsFreebsd => loader::OsFreebsd
     }
 }
 
diff --git a/src/librustc/middle/entry.rs b/src/librustc/middle/entry.rs
index 2ebb6e6926e..20b630e3063 100644
--- a/src/librustc/middle/entry.rs
+++ b/src/librustc/middle/entry.rs
@@ -11,6 +11,7 @@
 
 use driver::session;
 use driver::session::Session;
+use syntax::abi;
 use syntax::ast::{Crate, NodeId, item, item_fn};
 use syntax::ast_map;
 use syntax::attr;
@@ -48,7 +49,7 @@ pub fn find_entry_point(session: Session, crate: &Crate, ast_map: ast_map::map)
 
     // FIXME #4404 android JNI hacks
     if *session.building_library &&
-        session.targ_cfg.os != session::OsAndroid {
+        session.targ_cfg.os != abi::OsAndroid {
         // No need to find a main function
         return;
     }
@@ -151,7 +152,7 @@ fn configure_main(this: &mut EntryContext) {
         } else {
             // If we *are* building a library, then we're on android where we still might
             // optionally want to translate main $4404
-            assert_eq!(this.session.targ_cfg.os, session::OsAndroid);
+            assert_eq!(this.session.targ_cfg.os, abi::OsAndroid);
         }
     }
 }
diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index 37e4d4e82be..8c9cc3b8e13 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -85,7 +85,7 @@ use syntax::parse::token;
 use syntax::parse::token::{special_idents};
 use syntax::print::pprust::stmt_to_str;
 use syntax::{ast, ast_util, codemap, ast_map};
-use syntax::abi::{X86, X86_64, Arm, Mips, Rust, RustIntrinsic};
+use syntax::abi::{X86, X86_64, Arm, Mips, Rust, RustIntrinsic, OsWin32, OsAndroid};
 use syntax::visit;
 use syntax::visit::Visitor;
 
@@ -853,7 +853,8 @@ pub fn trans_external_path(ccx: &mut CrateContext, did: ast::DefId, t: ty::t) ->
     let name = csearch::get_symbol(ccx.sess.cstore, did);
     match ty::get(t).sty {
         ty::ty_bare_fn(ref fn_ty) => {
-            match fn_ty.abis.for_arch(ccx.sess.targ_cfg.arch) {
+            match fn_ty.abis.for_target(ccx.sess.targ_cfg.os,
+                                        ccx.sess.targ_cfg.arch) {
                 Some(Rust) | Some(RustIntrinsic) => {
                     get_extern_rust_fn(ccx, fn_ty.sig.inputs, fn_ty.sig.output, name, did)
                 }
@@ -2312,7 +2313,7 @@ fn finish_register_fn(ccx: @mut CrateContext, sp: Span, sym: ~str, node_id: ast:
     // FIXME #4404 android JNI hacks
     let is_entry = is_entry_fn(&ccx.sess, node_id) && (!*ccx.sess.building_library ||
                       (*ccx.sess.building_library &&
-                       ccx.sess.targ_cfg.os == session::OsAndroid));
+                       ccx.sess.targ_cfg.os == OsAndroid));
     if is_entry {
         create_entry_wrapper(ccx, sp, llfn);
     }
@@ -2981,7 +2982,7 @@ pub fn decl_crate_map(sess: session::Session, mapmeta: LinkMeta,
     };
     // On windows we'd like to export the toplevel cratemap
     // such that we can find it from libstd.
-    if targ_cfg.os == session::OsWin32 && "toplevel" == mapname {
+    if targ_cfg.os == OsWin32 && "toplevel" == mapname {
         lib::llvm::SetLinkage(map, lib::llvm::DLLExportLinkage);
     } else {
         lib::llvm::SetLinkage(map, lib::llvm::ExternalLinkage);
@@ -3157,7 +3158,7 @@ pub fn trans_crate(sess: session::Session,
     // __rust_crate_map_toplevel symbol (extra underscore) which it will
     // subsequently fail to find. So to mitigate that we just introduce
     // an alias from the symbol it expects to the one that actually exists.
-    if ccx.sess.targ_cfg.os == session::OsWin32 &&
+    if ccx.sess.targ_cfg.os == OsWin32 &&
        !*ccx.sess.building_library {
 
         let maptype = val_ty(ccx.crate_map).to_ref();
diff --git a/src/librustc/middle/trans/cabi_x86.rs b/src/librustc/middle/trans/cabi_x86.rs
index 244087f814c..f8cc246f682 100644
--- a/src/librustc/middle/trans/cabi_x86.rs
+++ b/src/librustc/middle/trans/cabi_x86.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 
-use driver::session::{OsWin32, OsMacos};
+use syntax::abi::{OsWin32, OsMacos};
 use lib::llvm::*;
 use super::cabi::*;
 use super::common::*;
diff --git a/src/librustc/middle/trans/foreign.rs b/src/librustc/middle/trans/foreign.rs
index ef843b56f4b..7da80507df0 100644
--- a/src/librustc/middle/trans/foreign.rs
+++ b/src/librustc/middle/trans/foreign.rs
@@ -32,7 +32,7 @@ use syntax::codemap::Span;
 use syntax::{ast};
 use syntax::{attr, ast_map};
 use syntax::parse::token::special_idents;
-use syntax::abi::{RustIntrinsic, Rust, Stdcall, Fastcall,
+use syntax::abi::{RustIntrinsic, Rust, Stdcall, Fastcall, System,
                   Cdecl, Aapcs, C, AbiSet};
 use util::ppaux::{Repr, UserString};
 use middle::trans::type_::Type;
@@ -75,8 +75,9 @@ struct LlvmSignature {
 
 pub fn llvm_calling_convention(ccx: &mut CrateContext,
                                abis: AbiSet) -> Option<CallConv> {
+    let os = ccx.sess.targ_cfg.os;
     let arch = ccx.sess.targ_cfg.arch;
-    abis.for_arch(arch).map(|abi| {
+    abis.for_target(os, arch).map(|abi| {
         match abi {
             RustIntrinsic => {
                 // Intrinsics are emitted by monomorphic fn
@@ -89,6 +90,9 @@ pub fn llvm_calling_convention(ccx: &mut CrateContext,
                     format!("Foreign functions with Rust ABI"));
             }
 
+            // It's the ABI's job to select this, not us.
+            System => ccx.sess.bug("System abi should be selected elsewhere"),
+
             Stdcall => lib::llvm::X86StdcallCallConv,
             Fastcall => lib::llvm::X86FastcallCallConv,
             C => lib::llvm::CCallConv,
diff --git a/src/libsyntax/abi.rs b/src/libsyntax/abi.rs
index ed20b160eb4..972d2f43e73 100644
--- a/src/libsyntax/abi.rs
+++ b/src/libsyntax/abi.rs
@@ -11,6 +11,9 @@
 use std::to_bytes;
 
 #[deriving(Eq)]
+pub enum Os { OsWin32, OsMacos, OsLinux, OsAndroid, OsFreebsd, }
+
+#[deriving(Eq)]
 pub enum Abi {
     // NB: This ordering MUST match the AbiDatas array below.
     // (This is ensured by the test indices_are_correct().)
@@ -24,6 +27,7 @@ pub enum Abi {
     // Multiplatform ABIs second
     Rust,
     C,
+    System,
     RustIntrinsic,
 }
 
@@ -76,6 +80,7 @@ static AbiDatas: &'static [AbiData] = &[
     // adjusting the indices below.
     AbiData {abi: Rust, name: "Rust", abi_arch: RustArch},
     AbiData {abi: C, name: "C", abi_arch: AllArch},
+    AbiData {abi: System, name: "system", abi_arch: AllArch},
     AbiData {abi: RustIntrinsic, name: "rust-intrinsic", abi_arch: RustArch},
 ];
 
@@ -125,6 +130,14 @@ impl Abi {
     pub fn name(&self) -> &'static str {
         self.data().name
     }
+
+    pub fn for_target(&self, os: Os, arch: Architecture) -> Abi {
+        match (*self, os, arch) {
+            (System, OsWin32, X86) => Stdcall,
+            (System, _, _) => C,
+            (me, _, _) => me,
+        }
+    }
 }
 
 impl Architecture {
@@ -196,7 +209,7 @@ impl AbiSet {
         self.bits == 0
     }
 
-    pub fn for_arch(&self, arch: Architecture) -> Option<Abi> {
+    pub fn for_target(&self, os: Os, arch: Architecture) -> Option<Abi> {
         // NB---Single platform ABIs come first
 
         let mut res = None;
@@ -210,7 +223,7 @@ impl AbiSet {
             }
         };
 
-        res
+        res.map(|r| r.for_target(os, arch))
     }
 
     pub fn check_valid(&self) -> Option<(Abi, Abi)> {
@@ -345,6 +358,11 @@ fn cannot_combine_rust_intrinsic_and_cdecl() {
 }
 
 #[test]
+fn can_combine_system_and_cdecl() {
+    can_combine(System, Cdecl);
+}
+
+#[test]
 fn can_combine_c_and_stdcall() {
     can_combine(C, Stdcall);
 }
@@ -382,36 +400,41 @@ fn abi_to_str_rust() {
 #[test]
 fn indices_are_correct() {
     for (i, abi_data) in AbiDatas.iter().enumerate() {
-        assert!(i == abi_data.abi.index());
+        assert_eq!(i, abi_data.abi.index());
     }
 
     let bits = 1 << (X86 as u32);
     let bits = bits | 1 << (X86_64 as u32);
-    assert!(IntelBits == bits);
+    assert_eq!(IntelBits, bits);
 
     let bits = 1 << (Arm as u32);
-    assert!(ArmBits == bits);
+    assert_eq!(ArmBits, bits);
 }
 
 #[cfg(test)]
-fn check_arch(abis: &[Abi], arch: Architecture, expect: Option<Abi>) {
+fn get_arch(abis: &[Abi], os: Os, arch: Architecture) -> Option<Abi> {
     let mut set = AbiSet::empty();
     for &abi in abis.iter() {
         set.add(abi);
     }
-    let r = set.for_arch(arch);
-    assert!(r == expect);
+    set.for_target(os, arch)
 }
 
 #[test]
 fn pick_multiplatform() {
-    check_arch([C, Cdecl], X86, Some(Cdecl));
-    check_arch([C, Cdecl], X86_64, Some(Cdecl));
-    check_arch([C, Cdecl], Arm, Some(C));
+    assert_eq!(get_arch([C, Cdecl], OsLinux, X86), Some(Cdecl));
+    assert_eq!(get_arch([C, Cdecl], OsLinux, X86_64), Some(Cdecl));
+    assert_eq!(get_arch([C, Cdecl], OsLinux, Arm), Some(C));
 }
 
 #[test]
 fn pick_uniplatform() {
-    check_arch([Stdcall], X86, Some(Stdcall));
-    check_arch([Stdcall], Arm, None);
+    assert_eq!(get_arch([Stdcall], OsLinux, X86), Some(Stdcall));
+    assert_eq!(get_arch([Stdcall], OsLinux, Arm), None);
+    assert_eq!(get_arch([System], OsLinux, X86), Some(C));
+    assert_eq!(get_arch([System], OsWin32, X86), Some(Stdcall));
+    assert_eq!(get_arch([System], OsWin32, X86_64), Some(C));
+    assert_eq!(get_arch([System], OsWin32, Arm), Some(C));
+    assert_eq!(get_arch([Stdcall], OsWin32, X86), Some(Stdcall));
+    assert_eq!(get_arch([Stdcall], OsWin32, X86_64), Some(Stdcall));
 }