Allow entry points without args: Array<String> (#2049)

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

@@ -36,16 +36,21 @@ internal fun findMainEntryPoint(context: Context): FunctionDescriptor? {
 
     val packageScope = context.builtIns.builtInsModule.getPackage(packageName).memberScope
 
-    val main = packageScope.getContributedFunctions(entryName,
-        NoLookupLocation.FROM_BACKEND).singleOrNull {
+    val candidates = packageScope.getContributedFunctions(entryName,
+        NoLookupLocation.FROM_BACKEND).filter {
             it.returnType?.isUnit() == true &&
-            it.hasSingleArrayOfStringParameter &&
             it.typeParameters.isEmpty() &&
             it.visibility.isPublicAPI
         }
-    if (main == null) {
-        context.reportCompilationError("Could not find '$entryName' in '$packageName' package.")
-    }
+
+    val main =
+        candidates.singleOrNull { it.hasSingleArrayOfStringParameter } ?:
+        candidates.singleOrNull { it.hasNoParameters } ?:
+        run {
+            context.reportCompilationError("Could not find '$entryName' in '$packageName' package.")
+            null
+        }
+
     return main
 }
 
@@ -73,3 +78,5 @@ private val KotlinType.isArrayOfString: Boolean
 private val FunctionDescriptor.hasSingleArrayOfStringParameter: Boolean
     get() = valueParameters.singleOrNull()?.type?.isArrayOfString ?: false
 
+private val FunctionDescriptor.hasNoParameters: Boolean
+    get() = valueParameters.isEmpty()

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

@@ -2618,9 +2618,9 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
     //-------------------------------------------------------------------------//
 
     private fun entryPointSelector(entryPoint: LLVMValueRef,
-        entryPointType: LLVMTypeRef, selectorName: String): LLVMValueRef {
+        entryPointType: LLVMTypeRef, selectorName: String, argCount: Int): LLVMValueRef {
 
-        assert(LLVMCountParams(entryPoint) == 1)
+        assert(LLVMCountParams(entryPoint) <= 1)
 
         val selector = LLVMAddFunction(context.llvmModule, selectorName, entryPointType)!!
         generateFunction(codegen, selector) {
@@ -2629,8 +2629,11 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
             // scheme for arguments guarantees, that reference is being held in C++
             // launcher, so we could optimize out creating slot for 'parameter' in
             // this function.
-            val parameter = LLVMGetParam(selector, 0)!!
-            call(entryPoint, listOf(parameter), Lifetime.IRRELEVANT, ExceptionHandler.Caller)
+            val parameters = if (argCount == 1)
+                listOf(LLVMGetParam(selector, 0)!!)
+            else
+                emptyList()
+            call(entryPoint, parameters, Lifetime.IRRELEVANT, ExceptionHandler.Caller)
             ret(null)
         }
         return selector
@@ -2644,8 +2647,10 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
         val entryPoint = codegen.llvmFunction(descriptor)
         val selectorName = "EntryPointSelector"
         val entryPointType = getFunctionType(entryPoint)
+        val argCount = descriptor.valueParameters.size
+        assert(argCount <= 1)
 
-        val selector = entryPointSelector(entryPoint, entryPointType, selectorName)
+        val selector = entryPointSelector(entryPoint, entryPointType, selectorName, argCount)
 
         LLVMSetLinkage(selector, LLVMLinkage.LLVMExternalLinkage)
     }

backend.native/tests/build.gradle

@@ -546,6 +546,17 @@ task entry2(type: LinkKonanTest) {
     flags = ["-entry", "foo"] 
 }
 
+task entry3(type: RunStandaloneKonanTest) {
+    goldValue = "Hello, without args.\n"
+    source = "runtime/basic/entry1.kt"
+    flags = ["-entry", "bar"]
+}
+
+task entry4(type: RunStandaloneKonanTest) {
+    goldValue = "This is main without args\n"
+    source = "runtime/basic/entry4.kt"
+}
+
 task readline0(type: RunStandaloneKonanTest) {
     goldValue = "41"
     testData = "41\r\n"

backend.native/tests/runtime/basic/entry1.kt

@@ -11,6 +11,10 @@ fun foo(args: Array<String>) {
     println("Hello.")
 }
 
+fun bar() {
+    println("Hello, without args.")
+}
+
 
 fun main(args: Array<String>) {
     fail()

backend.native/tests/runtime/basic/entry4.kt

@@ -0,0 +1,3 @@
+fun main() {
+    println("This is main without args")
+}