std/rustc/rustpkg/syntax: Support the extern mod = ... form

This commit allows you to write:

 extern mod x = "a/b/c";

which means rustc will search in the RUST_PATH for a package with
ID a/b/c, and bind it to the name `x` if it's found.

Incidentally, move get_relative_to from back::rpath into std::path

Author: catamorphism

doc/rust.md

@@ -744,7 +744,7 @@ There are several kinds of view item:
 ##### Extern mod declarations
 
 ~~~~~~~~ {.ebnf .gram}
-extern_mod_decl : "extern" "mod" ident [ '(' link_attrs ')' ] ? ;
+extern_mod_decl : "extern" "mod" ident [ '(' link_attrs ')' ] ? [ '=' string_lit ] ? ;
 link_attrs : link_attr [ ',' link_attrs ] + ;
 link_attr : ident '=' literal ;
 ~~~~~~~~
@@ -755,20 +755,34 @@ as the `ident` provided in the `extern_mod_decl`.
 
 The external crate is resolved to a specific `soname` at compile time,
 and a runtime linkage requirement to that `soname` is passed to the linker for
-loading at runtime. The `soname` is resolved at compile time by scanning the
-compiler's library path and matching the `link_attrs` provided in the
-`use_decl` against any `#link` attributes that were declared on the external
-crate when it was compiled. If no `link_attrs` are provided, a default `name`
-attribute is assumed, equal to the `ident` given in the `use_decl`.
-
-Three examples of `extern mod` declarations:
+loading at runtime.
+The `soname` is resolved at compile time by scanning the compiler's library path
+and matching the `link_attrs` provided in the `use_decl` against any `#link` attributes that
+were declared on the external crate when it was compiled.
+If no `link_attrs` are provided,
+a default `name` attribute is assumed,
+equal to the `ident` given in the `use_decl`.
+
+Optionally, an identifier in an `extern mod` declaration may be followed by an equals sign,
+then a string literal denoting a relative path on the filesystem.
+This path should exist in one of the directories in the Rust path,
+which by default contains the `.rust` subdirectory of the current directory and each of its parents,
+as well as any directories in the colon-separated (or semicolon-separated on Windows)
+list of paths that is the `RUST_PATH` environment variable.
+The meaning of `extern mod a = "b/c/d";`, supposing that `/a` is in the RUST_PATH,
+is that the name `a` should be taken as a reference to the crate whose absolute location is
+`/a/b/c/d`.
+
+Four examples of `extern mod` declarations:
 
 ~~~~~~~~{.xfail-test}
 extern mod pcre (uuid = "54aba0f8-a7b1-4beb-92f1-4cf625264841");
 
 extern mod extra; // equivalent to: extern mod extra ( name = "extra" );
 
 extern mod rustextra (name = "extra"); // linking to 'extra' under another name
+
+extern mod complicated_mod = "some-file/in/the-rust/path";
 ~~~~~~~~
 
 ##### Use declarations

src/librustc/back/link.rs

@@ -16,7 +16,7 @@ use lib::llvm::llvm;
 use lib::llvm::ModuleRef;
 use lib;
 use metadata::common::LinkMeta;
-use metadata::{encoder, csearch, cstore};
+use metadata::{encoder, csearch, cstore, filesearch};
 use middle::trans::context::CrateContext;
 use middle::trans::common::gensym_name;
 use middle::ty;
@@ -497,35 +497,40 @@ pub fn build_link_meta(sess: Session,
     struct ProvidedMetas {
         name: Option<@str>,
         vers: Option<@str>,
+        pkg_id: Option<@str>,
         cmh_items: ~[@ast::MetaItem]
     }
 
     fn provided_link_metas(sess: Session, c: &ast::Crate) ->
        ProvidedMetas {
         let mut name = None;
         let mut vers = None;
+        let mut pkg_id = None;
         let mut cmh_items = ~[];
         let linkage_metas = attr::find_linkage_metas(c.attrs);
         attr::require_unique_names(sess.diagnostic(), linkage_metas);
         foreach meta in linkage_metas.iter() {
             match meta.name_str_pair() {
                 Some((n, value)) if "name" == n => name = Some(value),
                 Some((n, value)) if "vers" == n => vers = Some(value),
+                Some((n, value)) if "package_id" == n => pkg_id = Some(value),
                 _ => cmh_items.push(*meta)
             }
         }
 
         ProvidedMetas {
             name: name,
             vers: vers,
+            pkg_id: pkg_id,
             cmh_items: cmh_items
         }
     }
 
     // This calculates CMH as defined above
     fn crate_meta_extras_hash(symbol_hasher: &mut hash::State,
                               cmh_items: ~[@ast::MetaItem],
-                              dep_hashes: ~[@str]) -> @str {
+                              dep_hashes: ~[@str],
+                              pkg_id: Option<@str>) -> @str {
         fn len_and_str(s: &str) -> ~str {
             fmt!("%u_%s", s.len(), s)
         }
@@ -563,7 +568,10 @@ pub fn build_link_meta(sess: Session,
             write_string(symbol_hasher, len_and_str(*dh));
         }
 
-    // tjc: allocation is unfortunate; need to change std::hash
+        for pkg_id.iter().advance |p| {
+            write_string(symbol_hasher, len_and_str(*p));
+        }
+
         return truncated_hash_result(symbol_hasher).to_managed();
     }
 
@@ -605,18 +613,20 @@ pub fn build_link_meta(sess: Session,
     let ProvidedMetas {
         name: opt_name,
         vers: opt_vers,
+        pkg_id: opt_pkg_id,
         cmh_items: cmh_items
     } = provided_link_metas(sess, c);
     let name = crate_meta_name(sess, output, opt_name);
     let vers = crate_meta_vers(sess, opt_vers);
     let dep_hashes = cstore::get_dep_hashes(sess.cstore);
     let extras_hash =
         crate_meta_extras_hash(symbol_hasher, cmh_items,
-                               dep_hashes);
+                               dep_hashes, opt_pkg_id);
 
     LinkMeta {
         name: name,
         vers: vers,
+        package_id: opt_pkg_id,
         extras_hash: extras_hash
     }
 }
@@ -939,6 +949,11 @@ pub fn link_args(sess: Session,
         args.push(~"-L" + path.to_str());
     }
 
+    let rustpath = filesearch::rust_path();
+    for rustpath.iter().advance |path| {
+        args.push(~"-L" + path.to_str());
+    }
+
     // The names of the extern libraries
     let used_libs = cstore::get_used_libraries(cstore);
     foreach l in used_libs.iter() { args.push(~"-l" + *l); }

src/librustc/back/rpath.rs

@@ -14,10 +14,7 @@ use metadata::cstore;
 use metadata::filesearch;
 
 use std::hashmap::HashSet;
-use std::num;
-use std::os;
-use std::util;
-use std::vec;
+use std::{num, os, path, uint, util, vec};
 
 fn not_win32(os: session::os) -> bool {
   os != session::os_win32
@@ -122,44 +119,10 @@ pub fn get_rpath_relative_to_output(os: session::os,
         session::os_win32 => util::unreachable()
     };
 
-    Path(prefix).push_rel(&get_relative_to(&os::make_absolute(output),
+    Path(prefix).push_rel(&path::get_relative_to(&os::make_absolute(output),
                                            &os::make_absolute(lib)))
 }
 
-// Find the relative path from one file to another
-pub fn get_relative_to(abs1: &Path, abs2: &Path) -> Path {
-    assert!(abs1.is_absolute);
-    assert!(abs2.is_absolute);
-    let abs1 = abs1.normalize();
-    let abs2 = abs2.normalize();
-    debug!("finding relative path from %s to %s",
-           abs1.to_str(), abs2.to_str());
-    let split1: &[~str] = abs1.components;
-    let split2: &[~str] = abs2.components;
-    let len1 = split1.len();
-    let len2 = split2.len();
-    assert!(len1 > 0);
-    assert!(len2 > 0);
-
-    let max_common_path = num::min(len1, len2) - 1;
-    let mut start_idx = 0;
-    while start_idx < max_common_path
-        && split1[start_idx] == split2[start_idx] {
-        start_idx += 1;
-    }
-
-    let mut path = ~[];
-    foreach _ in range(start_idx, len1 - 1) { path.push(~".."); };
-
-    path.push_all(split2.slice(start_idx, len2 - 1));
-
-    return if !path.is_empty() {
-        Path("").push_many(path)
-    } else {
-        Path(".")
-    }
-}
-
 fn get_absolute_rpaths(libs: &[Path]) -> ~[Path] {
     libs.iter().transform(|a| get_absolute_rpath(a)).collect()
 }
@@ -199,7 +162,6 @@ mod test {
     #[cfg(test)]
     #[cfg(test)]
     use back::rpath::{get_absolute_rpath, get_install_prefix_rpath};
-    use back::rpath::{get_relative_to, get_rpath_relative_to_output};
     use back::rpath::{minimize_rpaths, rpaths_to_flags};
     use driver::session;
 
@@ -244,78 +206,9 @@ mod test {
         assert_eq!(res, ~[Path("1a"), Path("2"), Path("4a"), Path("3")]);
     }
 
-    #[test]
-    fn test_relative_to1() {
-        let p1 = Path("/usr/bin/rustc");
-        let p2 = Path("/usr/lib/mylib");
-        let res = get_relative_to(&p1, &p2);
-        assert_eq!(res, Path("../lib"));
-    }
-
-    #[test]
-    fn test_relative_to2() {
-        let p1 = Path("/usr/bin/rustc");
-        let p2 = Path("/usr/bin/../lib/mylib");
-        let res = get_relative_to(&p1, &p2);
-        assert_eq!(res, Path("../lib"));
-    }
-
-    #[test]
-    fn test_relative_to3() {
-        let p1 = Path("/usr/bin/whatever/rustc");
-        let p2 = Path("/usr/lib/whatever/mylib");
-        let res = get_relative_to(&p1, &p2);
-        assert_eq!(res, Path("../../lib/whatever"));
-    }
-
-    #[test]
-    fn test_relative_to4() {
-        let p1 = Path("/usr/bin/whatever/../rustc");
-        let p2 = Path("/usr/lib/whatever/mylib");
-        let res = get_relative_to(&p1, &p2);
-        assert_eq!(res, Path("../lib/whatever"));
-    }
-
-    #[test]
-    fn test_relative_to5() {
-        let p1 = Path("/usr/bin/whatever/../rustc");
-        let p2 = Path("/usr/lib/whatever/../mylib");
-        let res = get_relative_to(&p1, &p2);
-        assert_eq!(res, Path("../lib"));
-    }
-
-    #[test]
-    fn test_relative_to6() {
-        let p1 = Path("/1");
-        let p2 = Path("/2/3");
-        let res = get_relative_to(&p1, &p2);
-        assert_eq!(res, Path("2"));
-    }
-
-    #[test]
-    fn test_relative_to7() {
-        let p1 = Path("/1/2");
-        let p2 = Path("/3");
-        let res = get_relative_to(&p1, &p2);
-        assert_eq!(res, Path(".."));
-    }
-
-    #[test]
-    fn test_relative_to8() {
-        let p1 = Path("/home/brian/Dev/rust/build/").push_rel(
-            &Path("stage2/lib/rustc/i686-unknown-linux-gnu/lib/librustc.so"));
-        let p2 = Path("/home/brian/Dev/rust/build/stage2/bin/..").push_rel(
-            &Path("lib/rustc/i686-unknown-linux-gnu/lib/libstd.so"));
-        let res = get_relative_to(&p1, &p2);
-        debug!("test_relative_tu8: %s vs. %s",
-               res.to_str(),
-               Path(".").to_str());
-        assert_eq!(res, Path("."));
-    }
-
     #[test]
     #[cfg(target_os = "linux")]
-    #[cfg(target_os = "andorid")]
+    #[cfg(target_os = "android")]
     fn test_rpath_relative() {
       let o = session::os_linux;
       let res = get_rpath_relative_to_output(o,

src/librustc/front/std_inject.rs

@@ -47,7 +47,7 @@ fn inject_libstd_ref(sess: Session, crate: &ast::Crate) -> @ast::Crate {
             let n1 = sess.next_node_id();
             let vi1 = ast::view_item {
                 node: ast::view_item_extern_mod(
-                        sess.ident_of("std"), ~[], n1),
+                        sess.ident_of("std"), None, ~[], n1),
                 attrs: ~[
                     attr::mk_attr(
                         attr::mk_name_value_item_str(@"vers", STD_VERSION.to_managed()))

src/librustc/front/test.rs

@@ -282,7 +282,7 @@ fn mk_std(cx: &TestCtxt) -> ast::view_item {
                                             cx.sess.next_node_id()))])
     } else {
         let mi = attr::mk_name_value_item_str(@"vers", @"0.8-pre");
-        ast::view_item_extern_mod(id_extra, ~[mi], cx.sess.next_node_id())
+        ast::view_item_extern_mod(id_extra, None, ~[mi], cx.sess.next_node_id())
     };
     ast::view_item {
         node: vi,

src/librustc/metadata/common.rs

@@ -185,5 +185,7 @@ pub static tag_item_impl_vtables: uint = 0x82;
 pub struct LinkMeta {
     name: @str,
     vers: @str,
+    // Optional package ID
+    package_id: Option<@str>, // non-None if this was a URL-like package ID
     extras_hash: @str
 }