Produce a warning in case we could not find an entry point.

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

@@ -16,13 +16,23 @@
 
 package org.jetbrains.kotlin.backend.konan
 
+/**
+ * This is a common ancestor of all Kotlin/Native exceptions.
+ */
+open class KonanException(message: String = "", cause: Throwable? = null) : Exception(message, cause)
+
 /**
  * Represents a compilation error caused by mistakes in an input file, e.g. undefined reference.
  */
-class KonanCompilationException(message: String = "", cause: Throwable? = null) : Exception(message, cause) {}
+class KonanCompilationException(message: String = "", cause: Throwable? = null) : KonanException(message, cause)
 
 /**
  * Internal compiler error: could not deserialize IR for inline function body.
  */
-class KonanIrDeserializationException(message: String = "", cause: Throwable? = null) : Exception(message, cause)
+class KonanIrDeserializationException(message: String = "", cause: Throwable? = null) : KonanException(message, cause)
+
+/**
+ * An error occured during external tool invocation. Such as non-zero exit code. 
+ */
+class KonanExternalToolFailure(message: String = "", cause: Throwable? = null) : KonanException(message, cause)
 

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

@@ -292,7 +292,7 @@ internal class LinkStage(val context: Context) {
     private val entryPointSelector: List<String>
         get() = if (nomain) emptyList() else platform.entrySelector
 
-    private fun link(objectFiles: List<ObjectFile>, libraryProvidedLinkerFlags: List<String>): ExecutableFile {
+    private fun link(objectFiles: List<ObjectFile>, libraryProvidedLinkerFlags: List<String>): ExecutableFile? {
         val executable = context.config.outputFile
 
         val linkCommand = platform.linkCommand(objectFiles, executable, optimize, debug) +
@@ -302,13 +302,16 @@ internal class LinkStage(val context: Context) {
                 platform.linkCommandSuffix() +
                 libraryProvidedLinkerFlags
 
-        runTool(*linkCommand.toTypedArray())
+        try {
+            runTool(*linkCommand.toTypedArray())
+        } catch (e: KonanExternalToolFailure) {
+            return null
+        }
         if (platform is MacOSBasedPlatform && context.shouldContainDebugInfo()) {
             if (context.phase?.verbose ?: false)
                 runTool(*platform.dsymutilDryRunVerboseCommand(executable).toTypedArray())
             runTool(*platform.dsymutilCommand(executable).toTypedArray())
         }
-
         return executable
     }
 
@@ -349,7 +352,7 @@ internal class LinkStage(val context: Context) {
 
     private fun runTool(vararg command: String) {
         val code = executeCommand(*command)
-        if (code != 0) error("The ${command[0]} command returned non-zero exit code: $code.")
+        if (code != 0) throw KonanExternalToolFailure("The ${command[0]} command returned non-zero exit code: $code.")
     }
 
     fun linkStage() {

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

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.backend.konan
 
 import org.jetbrains.kotlin.backend.common.CommonBackendContext
 import org.jetbrains.kotlin.cli.common.messages.CompilerMessageSeverity
+import org.jetbrains.kotlin.cli.common.messages.CompilerMessageLocation
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.declarations.IrFile
 import org.jetbrains.kotlin.ir.util.getCompilerMessageLocation
@@ -27,3 +28,11 @@ internal fun CommonBackendContext.reportCompilationError(message: String, irFile
     this.messageCollector.report(CompilerMessageSeverity.ERROR, message, location)
     throw KonanCompilationException()
 }
+
+internal fun CommonBackendContext.reportCompilationError(message: String) {
+    this.messageCollector.report(CompilerMessageSeverity.ERROR, message, null)
+}
+
+internal fun CommonBackendContext.reportCompilationWarning(message: String) {
+    this.messageCollector.report(CompilerMessageSeverity.WARNING, message, null)
+}

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

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.backend.konan.llvm
 
+import org.jetbrains.kotlin.backend.konan.reportCompilationError
 import org.jetbrains.kotlin.backend.konan.Context
 import org.jetbrains.kotlin.backend.konan.KonanConfigKeys
 import org.jetbrains.kotlin.backend.konan.descriptors.isArray
@@ -49,6 +50,9 @@ internal fun findMainEntryPoint(context: Context): FunctionDescriptor? {
             it.typeParameters.isEmpty() &&
             it.isExported()
         }
+    if (main == null) {
+        context.reportCompilationError("Could not find '$entryName' in '$packageName' package.")
+    }
     return main
 }