Introduced -nomain flag to disable generation of main(),

in assumption that it is provided by one of the libraries.

backend.native/cli.bc/src/org/jetbrains/kotlin/cli/bc/K2Native.kt

@@ -72,6 +72,7 @@ class K2Native : CLICompiler<K2NativeCompilerArguments>() {
                 put(NOSTDLIB, arguments.nostdlib)
                 put(COMPILE_AS_STDLIB, arguments.compileAsStdlib)
                 put(NOLINK, arguments.nolink)
+                put(NOMAIN, arguments.nomain)
                 put(LIBRARY_FILES,
                         arguments.libraries.toNonNullList())
 

backend.native/cli.bc/src/org/jetbrains/kotlin/cli/bc/K2NativeCompilerArguments.java

@@ -28,6 +28,9 @@ public class K2NativeCompilerArguments extends CommonCompilerArguments {
     @Argument(value = "nolink", description = "Don't link, just produce a bitcode file")
     public boolean nolink;
 
+    @Argument(value = "nomain", description = "Assume 'main' entry point to be provided by external libraries")
+    public boolean nomain;
+
     @Argument(value = "linkerArgs", description = "Pass arguments to linker", delimiter = " ")
     @ValueDescription("<arg>")
     public String[] linkerArguments;

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

@@ -27,6 +27,8 @@ class KonanConfigKeys {
                 = CompilerConfigurationKey.create("compile the module as stdlib")
         val NOLINK: CompilerConfigurationKey<Boolean> 
                 = CompilerConfigurationKey.create("don't link, only produce a bitcode file ")
+        val NOMAIN: CompilerConfigurationKey<Boolean> 
+                = CompilerConfigurationKey.create("assume 'main' entry point to be provided by external libraries")
         val LINKER_ARGS: CompilerConfigurationKey<List<String>>
                 = CompilerConfigurationKey.create("additional linker arguments")
         val TARGET: CompilerConfigurationKey<String?>

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

@@ -144,6 +144,7 @@ internal class LinkStage(val context: Context) {
     val optimize = config.get(KonanConfigKeys.OPTIMIZATION) ?: false
     val emitted = config.get(KonanConfigKeys.BITCODE_FILE)!!
     val nostdlib = config.get(KonanConfigKeys.NOSTDLIB) ?: false
+    val nomain = config.get(KonanConfigKeys.NOMAIN) ?: false
     val libraries = context.config.librariesToLink
 
     fun llvmLto(files: List<BitcodeFile>): ObjectFile {
@@ -188,11 +189,22 @@ internal class LinkStage(val context: Context) {
         return result
     }
 
+    // Ideally we'd want to have 
+    //      #pragma weak main = Konan_main
+    // in the launcher.cpp.
+    // Unfortunately, anything related to weak linking on MacOS
+    // only seems to be working with dynamic libraries.
+    // So we stick to "-alias _main _konan_main" on Mac.
+    // And just do the same on Linux.
+    val entryPointSelector: List<String> 
+        get() = if (nomain) listOf() 
+                else properties.propertyList("entrySelector.$suffix")
+
     fun link(objectFiles: List<ObjectFile>): ExecutableFile {
         val executable = config.get(KonanConfigKeys.EXECUTABLE_FILE)!!
-
         val linkCommand = platform.linkCommand(objectFiles, executable, optimize) +
-                asLinkerArgs(config.getNotNull(KonanConfigKeys.LINKER_ARGS))
+                asLinkerArgs(config.getNotNull(KonanConfigKeys.LINKER_ARGS)) +
+                entryPointSelector
 
         runTool(*linkCommand.toTypedArray())
 

backend.native/konan.properties

@@ -11,6 +11,7 @@ llvmLlcFlags.osx = -mtriple=x86_64-apple-macosx10.10.0 --disable-fp-elim
 linkerKonanFlags.osx = -lc++
 linkerOptimizationFlags.osx = -dead_strip
 osVersionMin.osx = -macosx_version_min 10.10.0
+entrySelector.osx = -alias _Konan_main _main
 
 // iphone
 arch.osx-ios = arm64
@@ -22,6 +23,7 @@ llvmLlcFlags.osx-ios = -mtriple=arm64-apple-ios5.0.0 --disable-fp-elim
 linkerKonanFlags.osx-ios = -lc++
 linkerOptimizationFlags.osx-ios = -dead_strip
 osVersionMin.osx-ios = -iphoneos_version_min 5.0.0
+entrySelector.osx-ios = -alias _Konan_main _main
 
 // iphone_sim
 arch.osx-ios-sim = x86_64
@@ -33,6 +35,7 @@ llvmLlcFlags.osx-ios-sim = -mtriple=x86_64-apple-ios5.0.0 --disable-fp-elim
 linkerKonanFlags.osx-ios-sim = -lc++
 linkerOptimizationFlags.osx-ios-sim = -dead_strip
 osVersionMin.osx-ios-sim = -ios_simulator_version_min 5.0.0
+entrySelector.osx-ios-sim = -alias _Konan_main _main
 
 // linux
 sysRoot.linux = target-gcc-toolchain-3-linux-x86-64/x86_64-unknown-linux-gnu/sysroot
@@ -44,4 +47,5 @@ llvmLlcFlags.linux = -march=x86-64
 linkerKonanFlags.linux = -Bstatic -lstdc++ -Bdynamic -ldl -lm -lpthread
 linkerOptimizationFlags.linux = --gc-sections
 pluginOptimizationFlags.linux = -plugin-opt=mcpu=x86-64 -plugin-opt=O3
+entrySelector.linux = --defsym main=Konan_main
 

runtime/src/launcher/cpp/main.cpp

@@ -1,5 +0,0 @@
-extern "C" int Konan_main(int argc, char** argv);
-
-int main(int argc, char** argv) {
-  return Konan_main(argc, argv);
-}