import libc::{c_int, c_uint, c_char};
import driver::session;
import session::session;
import lib::llvm::llvm;
import syntax::attr;
import middle::ty;
import metadata::{encoder, cstore};
import middle::trans::common::crate_ctxt;
import metadata::common::link_meta;
import std::map::hashmap;
import std::sha1::sha1;
import syntax::ast;
import syntax::print::pprust;
import lib::llvm::{ModuleRef, mk_pass_manager, mk_target_data, True, False,
        FileType};
import metadata::filesearch;
import syntax::ast_map::{path, path_mod, path_name};
import io::{Writer, WriterUtil};

enum output_type {
    output_type_none,
    output_type_bitcode,
    output_type_assembly,
    output_type_llvm_assembly,
    output_type_object,
    output_type_exe,
}

fn llvm_err(sess: session, msg: ~str) -> ! unsafe {
    let cstr = llvm::LLVMRustGetLastError();
    if cstr == ptr::null() {
        sess.fatal(msg);
    } else { sess.fatal(msg + ~": " + str::unsafe::from_c_str(cstr)); }
}

fn WriteOutputFile(sess:session,
        PM: lib::llvm::PassManagerRef, M: ModuleRef,
        Triple: *c_char,
        // FIXME: When #2334 is fixed, change
        // c_uint to FileType
        Output: *c_char, FileType: c_uint,
        OptLevel: c_int,
        EnableSegmentedStacks: bool) {
    let result = llvm::LLVMRustWriteOutputFile(
            PM, M, Triple, Output, FileType, OptLevel, EnableSegmentedStacks);
    if (!result) {
        llvm_err(sess, ~"Could not write output");
    }
}

mod write {
    fn is_object_or_assembly_or_exe(ot: output_type) -> bool {
        if ot == output_type_assembly || ot == output_type_object ||
               ot == output_type_exe {
            return true;
        }
        return false;
    }

    // Decides what to call an intermediate file, given the name of the output
    // and the extension to use.
    fn mk_intermediate_name(output_path: ~str, extension: ~str) ->
        ~str unsafe {
        let stem = match str::find_char(output_path, '.') {
          some(dot_pos) => str::slice(output_path, 0u, dot_pos),
          none => output_path
        };
        return stem + ~"." + extension;
    }

    fn run_passes(sess: session, llmod: ModuleRef, output: ~str) {
        let opts = sess.opts;
        if sess.time_llvm_passes() { llvm::LLVMRustEnableTimePasses(); }
        let mut pm = mk_pass_manager();
        let td = mk_target_data(
            sess.targ_cfg.target_strs.data_layout);
        llvm::LLVMAddTargetData(td.lltd, pm.llpm);
        // FIXME (#2812): run the linter here also, once there are llvm-c
        // bindings for it.

        // Generate a pre-optimization intermediate file if -save-temps was
        // specified.

        if opts.save_temps {
            match opts.output_type {
              output_type_bitcode => {
                if opts.optimize != session::No {
                    let filename = mk_intermediate_name(output, ~"no-opt.bc");
                    str::as_c_str(filename, |buf| {
                        llvm::LLVMWriteBitcodeToFile(llmod, buf)
                    });
                }
              }
              _ => {
                let filename = mk_intermediate_name(output, ~"bc");
                str::as_c_str(filename, |buf| {
                    llvm::LLVMWriteBitcodeToFile(llmod, buf)
                });
              }
            }
        }
        if !sess.no_verify() { llvm::LLVMAddVerifierPass(pm.llpm); }
        // FIXME (#2396): This is mostly a copy of the bits of opt's -O2 that
        // are available in the C api.
        // Also: We might want to add optimization levels like -O1, -O2,
        // -Os, etc
        // Also: Should we expose and use the pass lists used by the opt
        // tool?

        if opts.optimize != session::No {
            let fpm = mk_pass_manager();
            llvm::LLVMAddTargetData(td.lltd, fpm.llpm);

            let FPMB = llvm::LLVMPassManagerBuilderCreate();
            llvm::LLVMPassManagerBuilderSetOptLevel(FPMB, 2u as c_uint);
            llvm::LLVMPassManagerBuilderPopulateFunctionPassManager(FPMB,
                                                                    fpm.llpm);
            llvm::LLVMPassManagerBuilderDispose(FPMB);

            llvm::LLVMRunPassManager(fpm.llpm, llmod);
            let mut threshold = 225;
            if opts.optimize == session::Aggressive { threshold = 275; }

            let MPMB = llvm::LLVMPassManagerBuilderCreate();
            llvm::LLVMPassManagerBuilderSetOptLevel(MPMB,
                                                    opts.optimize as c_uint);
            llvm::LLVMPassManagerBuilderSetSizeLevel(MPMB, False);
            llvm::LLVMPassManagerBuilderSetDisableUnitAtATime(MPMB, False);
            llvm::LLVMPassManagerBuilderSetDisableUnrollLoops(MPMB, False);
            llvm::LLVMPassManagerBuilderSetDisableSimplifyLibCalls(MPMB,
                                                                   False);

            if threshold != 0u {
                llvm::LLVMPassManagerBuilderUseInlinerWithThreshold
                    (MPMB, threshold as c_uint);
            }
            llvm::LLVMPassManagerBuilderPopulateModulePassManager(MPMB,
                                                                  pm.llpm);

            llvm::LLVMPassManagerBuilderDispose(MPMB);
        }
        if !sess.no_verify() { llvm::LLVMAddVerifierPass(pm.llpm); }
        if is_object_or_assembly_or_exe(opts.output_type) {
            let LLVMOptNone       = 0 as c_int; // -O0
            let LLVMOptLess       = 1 as c_int; // -O1
            let LLVMOptDefault    = 2 as c_int; // -O2, -Os
            let LLVMOptAggressive = 3 as c_int; // -O3

            let mut CodeGenOptLevel = match opts.optimize {
              session::No => LLVMOptNone,
              session::Less => LLVMOptLess,
              session::Default => LLVMOptDefault,
              session::Aggressive => LLVMOptAggressive
            };

            let mut FileType;
            if opts.output_type == output_type_object ||
                   opts.output_type == output_type_exe {
               FileType = lib::llvm::ObjectFile;
            } else { FileType = lib::llvm::AssemblyFile; }
            // Write optimized bitcode if --save-temps was on.

            if opts.save_temps {
                // Always output the bitcode file with --save-temps

                let filename = mk_intermediate_name(output, ~"opt.bc");
                llvm::LLVMRunPassManager(pm.llpm, llmod);
                str::as_c_str(filename, |buf| {
                    llvm::LLVMWriteBitcodeToFile(llmod, buf)
                });
                pm = mk_pass_manager();
                // Save the assembly file if -S is used

                if opts.output_type == output_type_assembly {
                    let _: () = str::as_c_str(
                        sess.targ_cfg.target_strs.target_triple,
                        |buf_t| {
                            str::as_c_str(output, |buf_o| {
                                WriteOutputFile(
                                    sess,
                                    pm.llpm,
                                    llmod,
                                    buf_t,
                                    buf_o,
                                    lib::llvm::AssemblyFile as c_uint,
                                    CodeGenOptLevel,
                                    true)
                            })
                        });
                }


                // Save the object file for -c or --save-temps alone
                // This .o is needed when an exe is built
                if opts.output_type == output_type_object ||
                       opts.output_type == output_type_exe {
                    let _: () = str::as_c_str(
                        sess.targ_cfg.target_strs.target_triple,
                        |buf_t| {
                            str::as_c_str(output, |buf_o| {
                                WriteOutputFile(
                                    sess,
                                    pm.llpm,
                                    llmod,
                                    buf_t,
                                    buf_o,
                                    lib::llvm::ObjectFile as c_uint,
                                    CodeGenOptLevel,
                                    true)
                            })
                        });
                }
            } else {
                // If we aren't saving temps then just output the file
                // type corresponding to the '-c' or '-S' flag used

                let _: () = str::as_c_str(
                    sess.targ_cfg.target_strs.target_triple,
                    |buf_t| {
                        str::as_c_str(output, |buf_o| {
                            WriteOutputFile(
                                sess,
                                pm.llpm,
                                llmod,
                                buf_t,
                                buf_o,
                                FileType as c_uint,
                                CodeGenOptLevel,
                                true)
                        })
                    });
            }
            // Clean up and return

            llvm::LLVMDisposeModule(llmod);
            if sess.time_llvm_passes() { llvm::LLVMRustPrintPassTimings(); }
            return;
        }

        if opts.output_type == output_type_llvm_assembly {
            // Given options "-S --emit-llvm": output LLVM assembly
            str::as_c_str(output, |buf_o| {
                llvm::LLVMRustAddPrintModulePass(pm.llpm, llmod, buf_o)});
        } else {
            // If only a bitcode file is asked for by using the '--emit-llvm'
            // flag, then output it here
            llvm::LLVMRunPassManager(pm.llpm, llmod);
            str::as_c_str(output,
                        |buf| llvm::LLVMWriteBitcodeToFile(llmod, buf) );
        }

        llvm::LLVMDisposeModule(llmod);
        if sess.time_llvm_passes() { llvm::LLVMRustPrintPassTimings(); }
    }
}


/*
 * Name mangling and its relationship to metadata. This is complex. Read
 * carefully.
 *
 * The semantic model of Rust linkage is, broadly, that "there's no global
 * namespace" between crates. Our aim is to preserve the illusion of this
 * model despite the fact that it's not *quite* possible to implement on
 * modern linkers. We initially didn't use system linkers at all, but have
 * been convinced of their utility.
 *
 * There are a few issues to handle:
 *
 *  - Linkers operate on a flat namespace, so we have to flatten names.
 *    We do this using the C++ namespace-mangling technique. Foo::bar
 *    symbols and such.
 *
 *  - Symbols with the same name but different types need to get different
 *    linkage-names. We do this by hashing a string-encoding of the type into
 *    a fixed-size (currently 16-byte hex) cryptographic hash function (CHF:
 *    we use SHA1) to "prevent collisions". This is not airtight but 16 hex
 *    digits on uniform probability means you're going to need 2**32 same-name
 *    symbols in the same process before you're even hitting birthday-paradox
 *    collision probability.
 *
 *  - Symbols in different crates but with same names "within" the crate need
 *    to get different linkage-names.
 *
 * So here is what we do:
 *
 *  - Separate the meta tags into two sets: exported and local. Only work with
 *    the exported ones when considering linkage.
 *
 *  - Consider two exported tags as special (and mandatory): name and vers.
 *    Every crate gets them; if it doesn't name them explicitly we infer them
 *    as basename(crate) and "0.1", respectively. Call these CNAME, CVERS.
 *
 *  - Define CMETA as all the non-name, non-vers exported meta tags in the
 *    crate (in sorted order).
 *
 *  - Define CMH as hash(CMETA + hashes of dependent crates).
 *
 *  - Compile our crate to lib CNAME-CMH-CVERS.so
 *
 *  - Define STH(sym) as hash(CNAME, CMH, type_str(sym))
 *
 *  - Suffix a mangled sym with ::STH@CVERS, so that it is unique in the
 *    name, non-name metadata, and type sense, and versioned in the way
 *    system linkers understand.
 *
 */

fn build_link_meta(sess: session, c: ast::crate, output: ~str,
                   symbol_hasher: &hash::State) -> link_meta {

    type provided_metas =
        {name: option<~str>,
         vers: option<~str>,
         cmh_items: ~[@ast::meta_item]};

    fn provided_link_metas(sess: session, c: ast::crate) ->
       provided_metas {
        let mut name: option<~str> = none;
        let mut vers: option<~str> = none;
        let mut cmh_items: ~[@ast::meta_item] = ~[];
        let linkage_metas = attr::find_linkage_metas(c.node.attrs);
        attr::require_unique_names(sess.diagnostic(), linkage_metas);
        for linkage_metas.each |meta| {
            if attr::get_meta_item_name(meta) == ~"name" {
                match attr::get_meta_item_value_str(meta) {
                  some(v) => { name = some(v); }
                  none => vec::push(cmh_items, meta)
                }
            } else if attr::get_meta_item_name(meta) == ~"vers" {
                match attr::get_meta_item_value_str(meta) {
                  some(v) => { vers = some(v); }
                  none => vec::push(cmh_items, meta)
                }
            } else { vec::push(cmh_items, meta); }
        }
        return {name: name, vers: vers, cmh_items: cmh_items};
    }

    // This calculates CMH as defined above
    fn crate_meta_extras_hash(symbol_hasher: &hash::State,
                              _crate: ast::crate,
                              metas: provided_metas,
                              dep_hashes: ~[~str]) -> ~str {
        fn len_and_str(s: ~str) -> ~str {
            return fmt!{"%u_%s", str::len(s), s};
        }

        fn len_and_str_lit(l: ast::lit) -> ~str {
            return len_and_str(pprust::lit_to_str(@l));
        }

        let cmh_items = attr::sort_meta_items(metas.cmh_items);

        symbol_hasher.reset();
        for cmh_items.each |m_| {
            let m = m_;
            match m.node {
              ast::meta_name_value(key, value) => {
                symbol_hasher.write_str(len_and_str(key));
                symbol_hasher.write_str(len_and_str_lit(value));
              }
              ast::meta_word(name) => {
                symbol_hasher.write_str(len_and_str(name));
              }
              ast::meta_list(_, _) => {
                // FIXME (#607): Implement this
                fail ~"unimplemented meta_item variant";
              }
            }
        }

        for dep_hashes.each |dh| {
            symbol_hasher.write_str(len_and_str(dh));
        }

        return truncated_hash_result(symbol_hasher);
    }

    fn warn_missing(sess: session, name: ~str, default: ~str) {
        if !sess.building_library { return; }
        sess.warn(fmt!{"missing crate link meta `%s`, using `%s` as default",
                       name, default});
    }

    fn crate_meta_name(sess: session, _crate: ast::crate,
                       output: ~str, metas: provided_metas) -> ~str {
        return match metas.name {
              some(v) => v,
              none => {
                let name =
                    {
                        let mut os =
                            str::split_char(path::basename(output), '.');
                        if (vec::len(os) < 2u) {
                            sess.fatal(fmt!{"output file name `%s` doesn't\
                              appear to have an extension", output});
                        }
                        vec::pop(os);
                        str::connect(os, ~".")
                    };
                warn_missing(sess, ~"name", name);
                name
              }
            };
    }

    fn crate_meta_vers(sess: session, _crate: ast::crate,
                       metas: provided_metas) -> ~str {
        return match metas.vers {
              some(v) => v,
              none => {
                let vers = ~"0.0";
                warn_missing(sess, ~"vers", vers);
                vers
              }
            };
    }

    let provided_metas = provided_link_metas(sess, c);
    let name = crate_meta_name(sess, c, output, provided_metas);
    let vers = crate_meta_vers(sess, c, provided_metas);
    let dep_hashes = cstore::get_dep_hashes(sess.cstore);
    let extras_hash =
        crate_meta_extras_hash(symbol_hasher, c, provided_metas, dep_hashes);

    return {name: name, vers: vers, extras_hash: extras_hash};
}

fn truncated_hash_result(symbol_hasher: &hash::State) -> ~str unsafe {
    symbol_hasher.result_str()
}


// This calculates STH for a symbol, as defined above
fn symbol_hash(tcx: ty::ctxt, symbol_hasher: &hash::State, t: ty::t,
               link_meta: link_meta) -> ~str {
    // NB: do *not* use abbrevs here as we want the symbol names
    // to be independent of one another in the crate.

    symbol_hasher.reset();
    symbol_hasher.write_str(link_meta.name);
    symbol_hasher.write_str(~"-");
    symbol_hasher.write_str(link_meta.extras_hash);
    symbol_hasher.write_str(~"-");
    symbol_hasher.write_str(encoder::encoded_ty(tcx, t));
    let hash = truncated_hash_result(symbol_hasher);
    // Prefix with _ so that it never blends into adjacent digits

    return ~"_" + hash;
}

fn get_symbol_hash(ccx: @crate_ctxt, t: ty::t) -> ~str {
    match ccx.type_hashcodes.find(t) {
      some(h) => return h,
      none => {
        let hash = symbol_hash(ccx.tcx, ccx.symbol_hasher, t, ccx.link_meta);
        ccx.type_hashcodes.insert(t, hash);
        return hash;
      }
    }
}


// Name sanitation. LLVM will happily accept identifiers with weird names, but
// gas doesn't!
fn sanitize(s: ~str) -> ~str {
    let mut result = ~"";
    do str::chars_iter(s) |c| {
        match c {
          '@' => result += ~"_sbox_",
          '~' => result += ~"_ubox_",
          '*' => result += ~"_ptr_",
          '&' => result += ~"_ref_",
          ',' => result += ~"_",

          '{' | '(' => result += ~"_of_",
          'a' to 'z'
          | 'A' to 'Z'
          | '0' to '9'
          | '_' => str::push_char(result,c),
          _ => {
            if c > 'z' && char::is_XID_continue(c) {
                str::push_char(result,c);
            }
          }
        }
    }

    // Underscore-qualify anything that didn't start as an ident.
    if result.len() > 0u &&
        result[0] != '_' as u8 &&
        ! char::is_XID_start(result[0] as char) {
        return ~"_" + result;
    }

    return result;
}

fn mangle(sess: session, ss: path) -> ~str {
    // Follow C++ namespace-mangling style

    let mut n = ~"_ZN"; // Begin name-sequence.

    for ss.each |s| {
        match s { path_name(s) | path_mod(s) => {
          let sani = sanitize(sess.str_of(s));
          n += fmt!{"%u%s", str::len(sani), sani};
        } }
    }
    n += ~"E"; // End name-sequence.
    n
}

fn exported_name(sess: session, path: path, hash: ~str, vers: ~str) -> ~str {
    return mangle(sess,
                  vec::append_one(
                      vec::append_one(path, path_name(sess.ident_of(hash))),
                      path_name(sess.ident_of(vers))));
}

fn mangle_exported_name(ccx: @crate_ctxt, path: path, t: ty::t) -> ~str {
    let hash = get_symbol_hash(ccx, t);
    return exported_name(ccx.sess, path, hash, ccx.link_meta.vers);
}

fn mangle_internal_name_by_type_only(ccx: @crate_ctxt,
                                     t: ty::t, name: ~str) ->
   ~str {
    let s = util::ppaux::ty_to_short_str(ccx.tcx, t);
    let hash = get_symbol_hash(ccx, t);
    return mangle(ccx.sess,
                  ~[path_name(ccx.sess.ident_of(name)),
                    path_name(ccx.sess.ident_of(s)),
                    path_name(ccx.sess.ident_of(hash))]);
}

fn mangle_internal_name_by_path_and_seq(ccx: @crate_ctxt, path: path,
                                        flav: ~str) -> ~str {
    return mangle(ccx.sess,
                  vec::append_one(path, path_name(ccx.names(flav))));
}

fn mangle_internal_name_by_path(ccx: @crate_ctxt, path: path) -> ~str {
    return mangle(ccx.sess, path);
}

fn mangle_internal_name_by_seq(ccx: @crate_ctxt, flav: ~str) -> ~str {
    return fmt!("%s_%u", flav, ccx.names(flav));
}

// If the user wants an exe generated we need to invoke
// cc to link the object file with some libs
fn link_binary(sess: session,
               obj_filename: ~str,
               out_filename: ~str,
               lm: link_meta) {
    // Converts a library file name into a cc -l argument
    fn unlib(config: @session::config, filename: ~str) -> ~str unsafe {
        let rmlib = fn@(filename: ~str) -> ~str {
            let found = str::find_str(filename, ~"lib");
            if config.os == session::os_macos ||
                (config.os == session::os_linux ||
                 config.os == session::os_freebsd) &&
                option::is_some(found) && option::get(found) == 0u {
                return str::slice(filename, 3u, str::len(filename));
            } else { return filename; }
        };
        fn rmext(filename: ~str) -> ~str {
            let mut parts = str::split_char(filename, '.');
            vec::pop(parts);
            return str::connect(parts, ~".");
        }
        return match config.os {
              session::os_macos => rmext(rmlib(filename)),
              session::os_linux => rmext(rmlib(filename)),
              session::os_freebsd => rmext(rmlib(filename)),
              _ => rmext(filename)
            };
    }

    let output = if sess.building_library {
        let long_libname =
            os::dll_filename(fmt!{"%s-%s-%s",
                                  lm.name, lm.extras_hash, lm.vers});
        debug!{"link_meta.name:  %s", lm.name};
        debug!{"long_libname: %s", long_libname};
        debug!{"out_filename: %s", out_filename};
        debug!{"dirname(out_filename): %s", path::dirname(out_filename)};

        path::connect(path::dirname(out_filename), long_libname)
    } else { out_filename };

    log(debug, ~"output: " + output);

    // The default library location, we need this to find the runtime.
    // The location of crates will be determined as needed.
    let stage: ~str = ~"-L" + sess.filesearch.get_target_lib_path();

    // In the future, FreeBSD will use clang as default compiler.
    // It would be flexible to use cc (system's default C compiler)
    // instead of hard-coded gcc.
    // For win32, there is no cc command,
    // so we add a condition to make it use gcc.
    let cc_prog: ~str =
        if sess.targ_cfg.os == session::os_win32 { ~"gcc" } else { ~"cc" };
    // The invocations of cc share some flags across platforms

    let mut cc_args =
        vec::append(~[stage], sess.targ_cfg.target_strs.cc_args);
    vec::push(cc_args, ~"-o");
    vec::push(cc_args, output);
    vec::push(cc_args, obj_filename);

    let mut lib_cmd;
    let os = sess.targ_cfg.os;
    if os == session::os_macos {
        lib_cmd = ~"-dynamiclib";
    } else { lib_cmd = ~"-shared"; }

    // # Crate linking

    let cstore = sess.cstore;
    for cstore::get_used_crate_files(cstore).each |cratepath| {
        if str::ends_with(cratepath, ~".rlib") {
            vec::push(cc_args, cratepath);
            again;
        }
        let cratepath = cratepath;
        let dir = path::dirname(cratepath);
        if dir != ~"" { vec::push(cc_args, ~"-L" + dir); }
        let libarg = unlib(sess.targ_cfg, path::basename(cratepath));
        vec::push(cc_args, ~"-l" + libarg);
    }

    let ula = cstore::get_used_link_args(cstore);
    for ula.each |arg| { vec::push(cc_args, arg); }

    // # Extern library linking

    // User-supplied library search paths (-L on the cammand line) These are
    // the same paths used to find Rust crates, so some of them may have been
    // added already by the previous crate linking code. This only allows them
    // to be found at compile time so it is still entirely up to outside
    // forces to make sure that library can be found at runtime.

    let addl_paths = sess.opts.addl_lib_search_paths;
    for addl_paths.each |path| { vec::push(cc_args, ~"-L" + path); }

    // The names of the extern libraries
    let used_libs = cstore::get_used_libraries(cstore);
    for used_libs.each |l| { vec::push(cc_args, ~"-l" + l); }

    if sess.building_library {
        vec::push(cc_args, lib_cmd);

        // On mac we need to tell the linker to let this library
        // be rpathed
        if sess.targ_cfg.os == session::os_macos {
            vec::push(cc_args, ~"-Wl,-install_name,@rpath/"
                      + path::basename(output));
        }
    }

    if !sess.debugging_opt(session::no_rt) {
        // Always want the runtime linked in
        vec::push(cc_args, ~"-lrustrt");
    }

    // 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::os_linux {
        vec::push_all(cc_args, ~[~"-lrt", ~"-ldl"]);

        // LLVM implements the `frem` instruction as a call to `fmod`,
        // which lives in libm. Similar to above, on some linuxes we
        // have to be explicit about linking to it. See #2510
        vec::push(cc_args, ~"-lm");
    }

    if sess.targ_cfg.os == session::os_freebsd {
        vec::push_all(cc_args, ~[~"-pthread", ~"-lrt",
                                ~"-L/usr/local/lib", ~"-lexecinfo",
                                ~"-L/usr/local/lib/gcc46",
                                ~"-L/usr/local/lib/gcc44", ~"-lstdc++",
                                ~"-Wl,-z,origin",
                                ~"-Wl,-rpath,/usr/local/lib/gcc46",
                                ~"-Wl,-rpath,/usr/local/lib/gcc44"]);
    }

    // OS X 10.6 introduced 'compact unwind info', which is produced by the
    // linker from the dwarf unwind info. Unfortunately, it does not seem to
    // understand how to unwind our __morestack frame, so we have to turn it
    // off. This has impacted some other projects like GHC.
    if sess.targ_cfg.os == session::os_macos {
        vec::push(cc_args, ~"-Wl,-no_compact_unwind");
    }

    // Stack growth requires statically linking a __morestack function
    vec::push(cc_args, ~"-lmorestack");

    // FIXME (#2397): At some point we want to rpath our guesses as to where
    // extern libraries might live, based on the addl_lib_search_paths
    vec::push_all(cc_args, rpath::get_rpath_flags(sess, output));

    debug!{"%s link args: %s", cc_prog, str::connect(cc_args, ~" ")};
    // We run 'cc' here
    let prog = run::program_output(cc_prog, cc_args);
    if 0 != prog.status {
        sess.err(fmt!{"linking with `%s` failed with code %d",
                      cc_prog, prog.status});
        sess.note(fmt!{"%s arguments: %s",
                       cc_prog, str::connect(cc_args, ~" ")});
        sess.note(prog.err + prog.out);
        sess.abort_if_errors();
    }

    // Clean up on Darwin
    if sess.targ_cfg.os == session::os_macos {
        run::run_program(~"dsymutil", ~[output]);
    }

    // Remove the temporary object file if we aren't saving temps
    if !sess.opts.save_temps {
        if ! os::remove_file(obj_filename) {
            sess.warn(fmt!{"failed to delete object file `%s`",
                           obj_filename});
        }
    }
}
//
// Local Variables:
// mode: rust
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// End:
//