Redesign src/out scoping

We no longer enter paths from the src tree into scope map. Instead, targets
from the src tree now include their out tree directory (in essence their
"configuration"). This is then used to find a target's scope. See the
comment in class target for details.

The result of this change is that we can now again build multiple
configurations (out trees) for same project at once.

1 files changed, 76 insertions, 34 deletions

diff --git a/build2/search.cxx b/build2/search.cxx
index 7e85dab..cea7a7e 100644
--- a/build2/search.cxx
+++ b/build2/search.cxx
@@ -23,7 +23,7 @@ namespace build2
 
     const target_key& tk (pk.tk);
 
-    // Look for an existing target in this directory scope.
+    // Look for an existing target in the prerequisite's scope.
     //
     dir_path d;
     if (tk.dir->absolute ())
@@ -39,7 +39,23 @@ namespace build2
       }
     }
 
-    auto i (targets.find (*tk.type, d, *tk.name, tk.ext, trace));
+    // Prerequisite's out directory can be on of the following:
+    //
+    // empty    This means out is undetermined and we simply search for a
+    //          target that is in the out tree which happens to be indicated
+    //          by an empty value, so we can just pass this as is.
+    //
+    // absolute This is the "final" value that doesn't require any processing
+    //          and we simply use it as is.
+    //
+    // relative The out directory was specified using @-syntax as relative (to
+    //          the prerequisite's scope) and we need to complete it similar
+    //          to how we complete the relative dir above. This is @@ OUT TODO.
+    //
+    // What if we have user-supplied out but it is in-src build. Shouldn't we
+    // drop it?
+    //
+    auto i (targets.find (*tk.type, d, *tk.out, *tk.name, tk.ext, trace));
 
     if (i == targets.end ())
       return 0;
@@ -51,7 +67,7 @@ namespace build2
   }
 
   target*
-  search_existing_file (const prerequisite_key& cpk, const dir_paths& sp)
+  search_existing_file (const prerequisite_key& cpk)
   {
     tracer trace ("search_existing_file");
 
@@ -85,50 +101,73 @@ namespace build2
     // Make a copy with the updated extension.
     //
     const prerequisite_key pk {
-      cpk.proj, target_key {ctk.type, ctk.dir, ctk.name, ext}, cpk.scope};
+      cpk.proj, {ctk.type, ctk.dir, ctk.out, ctk.name, ext}, cpk.scope};
     const target_key& tk (pk.tk);
 
-    // Go over paths looking for a file.
+    // Check if there is a file.
     //
-    for (const dir_path& d: sp)
+    const dir_path& s (pk.scope->src_path ());
+    path f (s / *tk.dir / path (*tk.name));
+    f.normalize ();
+
+    if (!ext->empty ())
     {
-      path f (d / *tk.dir / path (*tk.name));
-      f.normalize ();
+      f += '.';
+      f += *ext;
+    }
 
-      if (!ext->empty ())
-      {
-        f += '.';
-        f += *ext;
-      }
+    timestamp mt (file_mtime (f));
 
-      timestamp mt (file_mtime (f));
+    if (mt == timestamp_nonexistent)
+    {
+      l4 ([&]{trace << "no existing file for prerequisite " << cpk;});
+      return nullptr;
+    }
 
-      if (mt == timestamp_nonexistent)
-        continue;
+    l5 ([&]{trace << "found existing file " << f << " for prerequisite "
+                  << cpk;});
 
-      l5 ([&]{trace << "found existing file " << f << " for prerequisite "
-                    << cpk;});
+    dir_path d (f.directory ());
 
-      // Find or insert. Note: using our updated extension.
-      //
-      auto r (targets.insert (*tk.type, f.directory (), *tk.name, ext, trace));
+    // Calculate the corresponding out. We have the same three options for the
+    // prerequisite's out directory as in search_existing_target(). If it is
+    // empty (undetermined), then we need to calculate it since this target
+    // will be from the src tree.
+    //
+    // In the other two cases we use the prerequisite's out (in case it is
+    // relative, we need to complete it, which is @@ OUT TODO). Note that we
+    // blindly trust the user's value which can be use for some interesting
+    // tricks, for example:
+    //
+    // ../cxx{foo}@./
+    //
+    dir_path out;
 
-      // Has to be a file_target.
-      //
-      file& t (dynamic_cast<file&> (r.first));
+    if (tk.out->empty ())
+    {
+      if (pk.scope->out_path () != s)
+        out = out_src (d, *pk.scope);
+    }
+    else
+      out = *tk.out;
 
-      l5 ([&]{trace << (r.second ? "new" : "existing") << " target " << t
-                    << " for prerequisite " << cpk;});
+    // Find or insert. Note that we are using our updated extension.
+    //
+    auto r (targets.insert (
+              *tk.type, move (d), move (out), *tk.name, ext, trace));
 
-      if (t.path ().empty ())
-        t.path (move (f));
+    // Has to be a file_target.
+    //
+    file& t (dynamic_cast<file&> (r.first));
 
-      t.mtime (mt);
-      return &t;
-    }
+    l5 ([&]{trace << (r.second ? "new" : "existing") << " target " << t
+                  << " for prerequisite " << cpk;});
+
+    if (t.path ().empty ())
+      t.path (move (f));
 
-    l4 ([&]{trace << "no existing file for prerequisite " << cpk;});
-    return nullptr;
+    t.mtime (mt);
+    return &t;
   }
 
   target&
@@ -156,7 +195,10 @@ namespace build2
 
     // Find or insert.
     //
-    auto r (targets.insert (*tk.type, move (d), *tk.name, tk.ext, trace));
+    // @@ OUT: same story as in search_existing_target() re out.
+    //
+    auto r (targets.insert (
+              *tk.type, move (d), *tk.out, *tk.name, tk.ext, trace));
     assert (r.second);
 
     target& t (r.first);