Check tasty file hash

Author: nicolasstucki

compiler/src/dotty/tools/backend/jvm/GenBCode.scala

@@ -26,6 +26,7 @@ import scala.tools.asm
 import scala.tools.asm.tree._
 import tpd._
 import StdNames._
+import dotty.tools.dotc.core.tasty.TastyPickler
 import dotty.tools.io._
 
 class GenBCode extends Phase {
@@ -221,9 +222,9 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
                 val outstream = new DataOutputStream(outTastyFile.bufferedOutput)
                 try outstream.write(binary)
                 finally outstream.close()
-                // TASTY attribute is created but 0 bytes are stored in it.
-                // A TASTY attribute has length 0 if and only if the .tasty file exists.
-                Array.empty[Byte]
+                // TASTY attribute is created but only the header bytes are stored in it.
+                // A TASTY attribute has length `headerSize` if and only if the .tasty file exists.
+                java.util.Arrays.copyOf(binary, TastyPickler.headerSize)
               } else {
                 // Create an empty file to signal that a tasty section exist in the corresponding .class
                 // This is much cheaper and simpler to check than doing classfile parsing

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -6,6 +6,7 @@ package classfile
 import Contexts._, Symbols._, Types._, Names._, StdNames._, NameOps._, Scopes._, Decorators._
 import SymDenotations._, unpickleScala2.Scala2Unpickler._, Constants._, Annotations._, util.Positions._
 import NameKinds.{ModuleClassName, DefaultGetterName}
+import dotty.tools.dotc.core.tasty.TastyPickler
 import ast.tpd._
 import java.io.{ ByteArrayInputStream, ByteArrayOutputStream, DataInputStream, File, IOException }
 import java.nio
@@ -785,7 +786,7 @@ class ClassfileParser(
 
       if (scan(tpnme.TASTYATTR)) {
         val attrLen = in.nextInt
-        if (attrLen == 0) { // A tasty attribute implies the existence of the .tasty file
+        if (attrLen == TastyPickler.headerSize) { // A tasty attribute implies the existence of the .tasty file
           val tastyBytes: Array[Byte] = classfile.underlyingSource match { // TODO: simplify when #3552 is fixed
             case None =>
               ctx.error("Could not load TASTY from .tasty for virtual file " + classfile)
@@ -816,8 +817,11 @@ class ClassfileParser(
                 Array.empty
               }
           }
-          if (tastyBytes.nonEmpty)
+          if (tastyBytes.nonEmpty) {
+            for (i <- 0 until TastyPickler.headerSize if tastyBytes(i) != in.nextByte)
+              ctx.error("Contents of TASTY file did not correspond to classfile. One of the files might be outdated or corrupted.")
             return unpickleTASTY(tastyBytes)
+          }
         }
         else return unpickleTASTY(in.nextBytes(attrLen))
       }

compiler/src/dotty/tools/dotc/core/tasty/TastyPickler.scala

@@ -29,12 +29,14 @@ class TastyPickler(val rootCls: ClassSymbol) {
     val uuidHi: Long = sections.iterator.map(x => pjwHash64(x._2.bytes)).fold(0L)(_ ^ _)
 
     val headerBuffer = {
-      val buf = new TastyBuffer(header.length + 24)
+      val buf = new TastyBuffer(TastyPickler.headerSize)
       for (ch <- header) buf.writeByte(ch.toByte)
+      // TODO use writeUncompressedLong to ensure that the header has a constant size across versions
       buf.writeNat(MajorVersion)
       buf.writeNat(MinorVersion)
       buf.writeUncompressedLong(uuidLow)
       buf.writeUncompressedLong(uuidHi)
+      assert(buf.length == TastyPickler.headerSize)
       buf
     }
 
@@ -90,3 +92,7 @@ class TastyPickler(val rootCls: ClassSymbol) {
     h
   }
 }
+
+object TastyPickler {
+  val headerSize = header.length + 18
+}