[Native] Enable real Android Native executables (#4624)

* Add AndroidProgramType binary option, override entry point, fix linker flags

* Add Konan_main_standalone entry point to the Android runtime

* Add compiler warning

* Make standalone programs print to stdout

* Fix warning message and readability

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/AndroidProgramType.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.backend.konan
+
+import org.jetbrains.kotlin.konan.target.LinkerOutputKind
+
+/**
+ * For historical reasons, Android Native executables can be of two types:
+ * - [Standalone] is a regular executable, in which the Konan entry point receives command line arguments as usual.
+ * - [NativeActivity] is a shared library in which the Konan entry point matches Android NDK's NativeActivity
+ *   signature ( https://developer.android.com/ndk/reference/group/native-activity#anativeactivity_createfunc ).
+ */
+enum class AndroidProgramType(
+        val konanMainOverride: String?,
+        val linkerOutputKindOverride: LinkerOutputKind?,
+        val consolePrintsToLogcat: Boolean
+) {
+
+    /** Regular executable. The runtime entry point name is not Konan_main for historical reasons. */
+    Standalone("Konan_main_standalone", null, false),
+
+    /** Native activity "executable" - a shared library with a specific entry point. */
+    NativeActivity(null, LinkerOutputKind.DYNAMIC_LIBRARY, true);
+
+    companion object {
+        val Default = NativeActivity
+    }
+}

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/BinaryOptions.kt

@@ -21,6 +21,8 @@ object BinaryOptions : BinaryOptionRegistry() {
     val stripDebugInfoFromNativeLibs by booleanOption()
 
     val sourceInfoType by option<SourceInfoType>()
+
+    val androidProgramType by option<AndroidProgramType>()
 }
 
 open class BinaryOption<T : Any>(

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/CompilerOutput.kt

@@ -85,8 +85,9 @@ private fun insertAliasToEntryPoint(context: Context) {
     if (context.config.produce != CompilerOutputKind.PROGRAM || nomain)
         return
     val module = context.llvmModule
-    val entryPoint = LLVMGetNamedFunction(module, "Konan_main")
-            ?: error("Module doesn't contain `Konan_main`")
+    val entryPointName = context.config.entryPointName
+    val entryPoint = LLVMGetNamedFunction(module, entryPointName)
+            ?: error("Module doesn't contain `$entryPointName`")
     LLVMAddAlias(module, LLVMTypeOf(entryPoint)!!, entryPoint, "main")
 }
 

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/KonanConfig.kt

@@ -275,6 +275,29 @@ class KonanConfig(val project: Project, val configuration: CompilerConfiguration
     internal val propertyLazyInitialization: Boolean get() = configuration.get(KonanConfigKeys.PROPERTY_LAZY_INITIALIZATION)!!
 
     internal val lazyIrForCaches: Boolean get() = configuration.get(KonanConfigKeys.LAZY_IR_FOR_CACHES)!!
+
+    internal val entryPointName: String by lazy {
+        if (target.family == Family.ANDROID) {
+            val androidProgramTypeOrNull = configuration.get(BinaryOptions.androidProgramType)
+            if (androidProgramTypeOrNull == null) {
+                configuration.report(CompilerMessageSeverity.WARNING, """
+                    Android Native executables are currently built as shared libraries with NativeActivity support, but the default behavior is going to change in 1.7.0 to build regular executables instead.
+                    To keep using NativeActivity support, add binaryOptions["androidProgramType"] = "nativeActivity" to your androidNative executable configuration block in Gradle script:
+                    binaries {
+                        executable {
+                            binaryOptions["androidProgramType"] = "nativeActivity"
+                        }
+                    }
+                    See https://youtrack.jetbrains.com/issue/KT-49406 for more details.
+                """.trimIndent())
+            }
+            val androidProgramType = androidProgramTypeOrNull ?: AndroidProgramType.Default
+            if (androidProgramType.konanMainOverride != null) {
+                return@lazy androidProgramType.konanMainOverride
+            }
+        }
+        "Konan_main"
+    }
 }
 
 fun CompilerConfiguration.report(priority: CompilerMessageSeverity, message: String)

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/Linker.kt

@@ -21,7 +21,16 @@ internal fun determineLinkerOutput(context: Context): LinkerOutputKind =
             CompilerOutputKind.DYNAMIC -> LinkerOutputKind.DYNAMIC_LIBRARY
             CompilerOutputKind.STATIC_CACHE,
             CompilerOutputKind.STATIC -> LinkerOutputKind.STATIC_LIBRARY
-            CompilerOutputKind.PROGRAM -> LinkerOutputKind.EXECUTABLE
+            CompilerOutputKind.PROGRAM -> run {
+                if (context.config.target.family == Family.ANDROID) {
+                    val configuration = context.config.configuration
+                    val androidProgramType = configuration.get(BinaryOptions.androidProgramType) ?: AndroidProgramType.Default
+                    if (androidProgramType.linkerOutputKindOverride != null) {
+                        return@run androidProgramType.linkerOutputKindOverride
+                    }
+                }
+                LinkerOutputKind.EXECUTABLE
+            }
             else -> TODO("${context.config.produce} should not reach native linker stage")
         }
 

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt

@@ -2745,6 +2745,11 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
                             functionType(int32Type, false, int8TypePtr, int8TypePtr, int32Type))
             overrideRuntimeGlobal("Kotlin_getSourceInfo_Function", constValue(getSourceInfoFunction!!))
         }
+        if (context.config.target.family == Family.ANDROID && context.config.produce == CompilerOutputKind.PROGRAM) {
+            val configuration = context.config.configuration
+            val programType = configuration.get(BinaryOptions.androidProgramType) ?: AndroidProgramType.Default
+            overrideRuntimeGlobal("Kotlin_printToAndroidLogcat", Int32(if (programType.consolePrintsToLogcat) 1 else 0))
+        }
     }
 
     //-------------------------------------------------------------------------//