runtime/build.gradle: extract bitcode compilation to custom task class

buildSrc/src/main/groovy/org/jetbrains/kotlin/CompileToBitcode.groovy

@@ -0,0 +1,93 @@
+package org.jetbrains.kotlin
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.InputDirectory
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.TaskAction
+
+class CompileCppToBitcode extends DefaultTask {
+    private String name = "main"
+    private File srcRoot;
+
+    private List<String> compilerArgs = []
+    private List<String> linkerArgs = []
+
+    @InputDirectory
+    File getSrcRoot() {
+        return srcRoot ?: project.file("src/$name")
+    }
+
+    @OutputFile
+    File getOutFile() {
+        return new File(project.buildDir, "${name}.bc")
+    }
+
+    private File getSrcDir() {
+        return new File(this.getSrcRoot(), "cpp")
+    }
+
+    private File getHeadersDir() {
+        return new File(this.getSrcRoot(), "headers")
+    }
+
+    private File getObjDir() {
+        return new File(project.buildDir, name)
+    }
+
+    void name(String value) {
+        name = value
+    }
+
+    void srcRoot(File value) {
+        srcRoot = value
+    }
+
+    private List<String> getCompilerArgs() {
+        return compilerArgs
+    }
+
+    private List<String> getLinkerArgs() {
+        return linkerArgs
+    }
+
+    void compilerArgs(String... args) {
+        compilerArgs.addAll(args)
+    }
+
+    void linkerArgs(String... args) {
+        linkerArgs.addAll(args)
+    }
+
+    @TaskAction
+    void compile() {
+        // the strange code below seems to be required due to some Gradle (Groovy?) behaviour
+        File headersDir = this.getHeadersDir()
+        File srcDir = this.getSrcDir()
+        List<String> compilerArgs = this.getCompilerArgs()
+        List<String> linkerArgs = this.getLinkerArgs()
+        File objDir = this.getObjDir()
+        objDir.mkdirs()
+
+        project.exec {
+            workingDir objDir
+            executable "$project.llvmInstallPath/bin/clang++"
+            args '-std=c++11'
+
+            args compilerArgs
+
+            args "-I$headersDir"
+
+            args '-c', '-emit-llvm'
+            args project.fileTree(srcDir).include('**/*.cpp')
+        }
+
+        project.exec {
+            executable "$project.llvmInstallPath/bin/llvm-link"
+            args project.fileTree(objDir).include('**/*.bc')
+
+            args linkerArgs
+
+            args '-o', outFile
+        }
+    }
+}

runtime/build.gradle

@@ -1,39 +1,12 @@
+import org.jetbrains.kotlin.CompileCppToBitcode
+
 // TODO: consider using some Gradle plugins to build and test
 
-def srcDir = 'src/main/cpp'
-def objDir = "$buildDir/bitcode"
-def outFile = "$buildDir/runtime.bc"
 
-task compile(type: Exec) {
-    doFirst {
-         new File(objDir).mkdirs()
-    }
+task build(type: CompileCppToBitcode) {
+    name 'runtime'
+    srcRoot file('src/main')
 
-    inputs.dir srcDir
-    outputs.dir objDir
-
-    workingDir objDir
-
-    executable "$llvmInstallPath/bin/clang"
-    args '-std=c++11'
-
-    args '-c', '-emit-llvm'
-
-    args fileTree(srcDir).include('**/*.cpp')
-}
-
-task build(type: Exec) {
-    dependsOn compile
-
-    inputs.dir objDir
-    outputs.file outFile
-
-    executable "$llvmInstallPath/bin/llvm-link"
-    args '-o', outFile
-
-    doFirst {
-        args fileTree(objDir).include('**/*.bc')
-    }
 }
 
 task test {
@@ -44,7 +17,7 @@ task test {
 	    commandLine "$llvmInstallPath/bin/clang", 'src/test/c/main.c', '-c', '-emit-llvm', '-o', "$buildDir/main.bc"
 	}
         exec {
-	    commandLine "$llvmInstallPath/bin/clang++", outFile, "$buildDir/main.bc", '-o', "$buildDir/main"
+	    commandLine "$llvmInstallPath/bin/clang++", build.outFile, "$buildDir/main.bc", '-o', "$buildDir/main"
 	}
 	exec {
 	    workingDir buildDir