stage2: add support for start.zig

This adds a simplified start2.zig that the current stage2 compiler is
able to generate code for.

1 files changed, 25 insertions, 0 deletions

diff --git a/src/Package.zig b/src/Package.zig
index 03c9e9ea3d..d5960dcf9a 100644
--- a/src/Package.zig
+++ b/src/Package.zig
@@ -15,6 +15,9 @@ root_src_path: []const u8,
 table: Table = .{},
 parent: ?*Package = null,
 
+// Used when freeing packages
+seen: bool = false,
+
 /// Allocate a Package. No references to the slices passed are kept.
 pub fn create(
     gpa: *Allocator,
@@ -55,6 +58,14 @@ pub fn destroy(pkg: *Package, gpa: *Allocator) void {
         pkg.root_src_directory.handle.close();
     }
 
+    // First we recurse into all the packages and remove packages from the tables
+    // once we have seen it before. We do this to make sure that that
+    // a package can only be found once in the whole tree.
+    if (!pkg.seen) {
+        pkg.seen = true;
+        pkg.markSeen(gpa);
+    }
+
     {
         var it = pkg.table.iterator();
         while (it.next()) |kv| {
@@ -69,6 +80,20 @@ pub fn destroy(pkg: *Package, gpa: *Allocator) void {
     gpa.destroy(pkg);
 }
 
+fn markSeen(pkg: *Package, gpa: *Allocator) void {
+    var it = pkg.table.iterator();
+    while (it.next()) |kv| {
+        if (pkg != kv.value) {
+            if (kv.value.seen) {
+                pkg.table.removeAssertDiscard(kv.key);
+            } else {
+                kv.value.seen = true;
+                kv.value.markSeen(gpa);
+            }
+        }
+    }
+}
+
 pub fn add(pkg: *Package, gpa: *Allocator, name: []const u8, package: *Package) !void {
     try pkg.table.ensureCapacity(gpa, pkg.table.count() + 1);
     const name_dupe = try mem.dupe(gpa, u8, name);