From bc96e42585800d615255d53349da000bf995b2e9 Mon Sep 17 00:00:00 2001
From: Martin Petrov <mpetrov@google.com>
Date: Wed, 25 Mar 2020 13:22:09 -0400
Subject: [PATCH] Produce deterministic klib files.

Build systems like bazel rely on the output of a compilation being
deterministic. File checksums determine when an artifact is safe to
cache across builds. One can produce a klib deterministically by using a
fixed timestamp during klib compression.

Before this change:

```
$ kotlinc-native  -produce library -output /tmp/first/color.klib Color.kt
$ kotlinc-native  -produce library -output /tmp/second/color.klib Color.kt
$ shasum  /tmp/first/color.klib /tmp/second/color.klib
bc3f73678ff025cfbec9009f9a851a8ca74e1037  /tmp/first/color.klib
65aa37886fbd53285f2e449a4dab6a2ad02732e6  /tmp/second/color.klib
```

After this change:

```
$ kotlinc-native  -produce library -output /tmp/first/color.klib Color.kt
$ kotlinc-native  -produce library -output /tmp/second/color.klib Color.kt
$ shasum  /tmp/first/color.klib /tmp/second/color.klib
fcba304493916ae34d372188991f87b60a113cf3  /tmp/first/color.klib
fcba304493916ae34d372188991f87b60a113cf3  /tmp/second/color.klib
```
---
 .../src/org/jetbrains/kotlin/konan/file/File.kt      | 12 +++++++++---
 .../src/org/jetbrains/kotlin/konan/file/ZipUtil.kt   |  4 +++-
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/compiler/util-io/src/org/jetbrains/kotlin/konan/file/File.kt b/compiler/util-io/src/org/jetbrains/kotlin/konan/file/File.kt
index 2bb6fdc12b2..af139394705 100644
--- a/compiler/util-io/src/org/jetbrains/kotlin/konan/file/File.kt
+++ b/compiler/util-io/src/org/jetbrains/kotlin/konan/file/File.kt
@@ -14,7 +14,9 @@ import java.lang.Exception
 import java.nio.MappedByteBuffer
 import java.nio.channels.FileChannel
 import java.nio.file.*
+import java.nio.file.attribute.BasicFileAttributeView
 import java.nio.file.attribute.BasicFileAttributes
+import java.nio.file.attribute.FileTime
 
 data class File constructor(internal val javaPath: Path) {
     constructor(parent: Path, child: String): this(parent.resolve(child))
@@ -62,10 +64,10 @@ data class File constructor(internal val javaPath: Path) {
         Files.copy(javaPath, destination.javaPath, StandardCopyOption.REPLACE_EXISTING)
     }
 
-    fun recursiveCopyTo(destination: File) {
+    fun recursiveCopyTo(destination: File, resetTimeAttributes: Boolean = false) {
         val sourcePath = javaPath
         val destPath = destination.javaPath
-        sourcePath.recursiveCopyTo(destPath)
+        sourcePath.recursiveCopyTo(destPath, resetTimeAttributes = resetTimeAttributes)
     }
 
     fun mkdirs() = Files.createDirectories(javaPath)
@@ -185,7 +187,7 @@ fun createTempFile(name: String, suffix: String? = null)
 fun createTempDir(name: String): File
         = Files.createTempDirectory(name).File()
 
-fun Path.recursiveCopyTo(destPath: Path) {
+fun Path.recursiveCopyTo(destPath: Path, resetTimeAttributes: Boolean = false) {
     val sourcePath = this
     Files.walk(sourcePath).forEach next@ { oldPath ->
 
@@ -202,6 +204,10 @@ fun Path.recursiveCopyTo(destPath: Path) {
         } else {
             Files.copy(oldPath, newPath, StandardCopyOption.REPLACE_EXISTING)
         }
+        if (resetTimeAttributes) {
+            val zero = FileTime.fromMillis(0)
+            Files.getFileAttributeView(newPath, BasicFileAttributeView::class.java).setTimes(zero, zero, zero);
+        }
     }
 }
 
diff --git a/compiler/util-io/src/org/jetbrains/kotlin/konan/file/ZipUtil.kt b/compiler/util-io/src/org/jetbrains/kotlin/konan/file/ZipUtil.kt
index 65fea7bbdb6..a94ce04f054 100644
--- a/compiler/util-io/src/org/jetbrains/kotlin/konan/file/ZipUtil.kt
+++ b/compiler/util-io/src/org/jetbrains/kotlin/konan/file/ZipUtil.kt
@@ -41,7 +41,9 @@ private fun File.toPath() = Paths.get(this.path)
 
 fun File.zipDirAs(unixFile: File) {
     unixFile.withMutableZipFileSystem {
-        this.recursiveCopyTo(it.file("/"))
+        // Time attributes are not preserved to ensure that the output zip file bytes deterministic for a fixed set of
+        // input files.
+        this.recursiveCopyTo(it.file("/"), resetTimeAttributes = true)
     }
 }