From 9731c203bde0dd1aa9e2d2a0ec9acc8582614865 Mon Sep 17 00:00:00 2001
From: str4d <str4d@mail.i2p>
Date: Sun, 17 Feb 2019 02:13:32 +0000
Subject: [PATCH] Gradle: Improve cross-compilation support

JDK 9+ have a --release flag that correctly configures the bootClasspath.
For JDK 8 we now enforce manual configuration.
---
 build.gradle      | 31 ++++++++++++++++++++++++++++++-
 gradle.properties |  2 +-
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/build.gradle b/build.gradle
index 9f7b1e7f45..cd78dc3589 100644
--- a/build.gradle
+++ b/build.gradle
@@ -32,6 +32,14 @@ String getBuildExtra() {
     buildExtra
 }
 
+String compat(String src) {
+    if (src.contains('.')) {
+        src.substring(src.lastIndexOf('.') + 1)
+    } else {
+        src
+    }
+}
+
 def releaseVersion = getReleaseVersion()
 def buildVersion = getBuildVersion()
 def buildExtra = getBuildExtra()
@@ -63,11 +71,32 @@ configure(javaProjects) {
     }
 
     sourceCompatibility = 1.7
-    // Set i2pBootClasspath=/path/to/rt.jar:/path/to/jce.jar in ~/.gradle/gradle.properties if needed
+    targetCompatibility = 1.7
+
+    def i2pBootClasspath
+    // Set java7BootClasspath=/path/to/rt.jar:/path/to/jce.jar in ~/.gradle/gradle.properties if needed
+    if (java7BootClasspath) {
+        i2pBootClasspath = java7BootClasspath
+    } else {
+        def java7Home = System.getenv("JAVA7_HOME")
+        if (java7Home) {
+            i2pBootClasspath = "${java7Home}/jre/lib/jce.jar:${java7Home}/jre/lib/rt.jar"
+        }
+    }
+
     if (i2pBootClasspath) {
         tasks.withType(AbstractCompile, { AbstractCompile ac ->
             ac.options.bootstrapClasspath = files(i2pBootClasspath)
         })
+    } else {
+        if (JavaVersion.current().java8Compatible && !JavaVersion.current().java9Compatible) {
+            throw new GradleException("Set java7BootClasspath property or JAVA7_HOME environment variable to enable cross-compilation, or run Gradle with JDK 9+")
+        }
+        tasks.withType(JavaCompile) {
+            def version = compat(sourceCompatibility)
+            logger.info("Configuring $name to use --release $version")
+            options.compilerArgs.addAll(['--release', version])
+        }
     }
 }
 
diff --git a/gradle.properties b/gradle.properties
index 63fe06e83e..de9bef3372 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,2 +1,2 @@
 # Override these in ~/.gradle/gradle.properties if necessary
-i2pBootClasspath=
+java7BootClasspath=