Prefix exported symbols via UnmanagedCallersOnly attribute

src/mono/mono/mini/aot-compiler.c

@@ -5244,9 +5244,9 @@ MONO_RESTORE_WARNING
 				for (j = 0; j < decoded_args->named_args_num; ++j) {
 					if (decoded_args->named_args_info [j].field && !strcmp (decoded_args->named_args_info [j].field->name, "EntryPoint")) {
 						named = (const char *)decoded_args->named_args[j]->value.primitive;
-						slen = mono_metadata_decode_value (named, &named);
+						slen = mono_metadata_decode_value (named, &named) + (int)strlen(acfg->user_symbol_prefix);
 						export_name = (char *)g_malloc (slen + 1);
-						memcpy (export_name, named, slen);
+						sprintf (export_name, "%s%s", acfg->user_symbol_prefix, named);
 						export_name [slen] = 0;
 					}
 				}
@@ -5258,7 +5258,7 @@ MONO_RESTORE_WARNING
 				add_method (acfg, wrapper);
 				if (export_name) {
 					g_hash_table_insert (acfg->export_names, wrapper, export_name);
-					g_string_append_printf (export_symbols, "%s%s\n", acfg->user_symbol_prefix, export_name);
+					g_string_append_printf (export_symbols, "%s\n", export_name);
 				}
 			}
 

src/tests/FunctionalTests/iOS/Device/ExportManagedSymbols/ILLink.Descriptors.xml

@@ -0,0 +1,8 @@
+<linker>
+  <!-- this is here to show how to configure the trimming -->
+  <assembly fullname="iOS.Device.ExportManagedSymbols.Test">
+    <type fullname="Program">
+        <method name="ManagedMethod" />
+    </type>
+  </assembly>
+</linker>

src/tests/FunctionalTests/iOS/Device/ExportManagedSymbols/Program.cs

@@ -0,0 +1,25 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Runtime.InteropServices;
+
+public static class Program
+{
+    [DllImport("__Internal")]
+    public static extern void mono_ios_set_summary (string value);
+
+    [UnmanagedCallersOnly(EntryPoint="exposed_managed_method")]
+    public static int ManagedMethod() => 42;
+
+    public static async Task<int> Main(string[] args)
+    {
+        mono_ios_set_summary($"Starting functional test");
+        Console.WriteLine("Done!");
+        await Task.Delay(5000);
+
+        return 42;
+    }
+}

src/tests/FunctionalTests/iOS/Device/ExportManagedSymbols/iOS.Device.ExportManagedSymbols.Test.csproj

@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk" TreatAsLocalProperty="MonoForceInterpreter">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <MonoForceInterpreter>false</MonoForceInterpreter>
+    <RunAOTCompilation>true</RunAOTCompilation>
+    <TestRuntime>true</TestRuntime>
+    <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
+    <TargetOS Condition="'$(TargetOS)' == ''">iOS</TargetOS>
+    <MainLibraryFileName>iOS.Device.ExportManagedSymbols.Test.dll</MainLibraryFileName>
+    <IncludesTestRunner>false</IncludesTestRunner>
+    <ExpectedExitCode>42</ExpectedExitCode>
+    <EnableAggressiveTrimming>true</EnableAggressiveTrimming>
+    <MonoEnableLLVM>true</MonoEnableLLVM>
+    <NativeMainSource>$(MSBuildProjectDirectory)/main.m</NativeMainSource>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Program.cs" />
+    <!-- Prevent trimming of the exposed managed method via ILLinker -->
+    <TrimmerRootDescriptor Include="$(MSBuildProjectDirectory)/ILLink.Descriptors.xml" />
+  </ItemGroup>
+</Project>

src/tests/FunctionalTests/iOS/Device/ExportManagedSymbols/main.m

@@ -0,0 +1,106 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#import <UIKit/UIKit.h>
+#import <dlfcn.h>
+#import "runtime.h"
+#include <TargetConditionals.h>
+
+@interface ViewController : UIViewController
+@end
+
+@interface AppDelegate : UIResponder <UIApplicationDelegate>
+@property (strong, nonatomic) UIWindow *window;
+@property (strong, nonatomic) ViewController *controller;
+@end
+
+@implementation AppDelegate
+- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
+    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
+    self.controller = [[ViewController alloc] initWithNibName:nil bundle:nil];
+    self.window.rootViewController = self.controller;
+    [self.window makeKeyAndVisible];
+    return YES;
+}
+@end
+
+UILabel *summaryLabel;
+UITextView* logLabel;
+
+@implementation ViewController
+
+- (void)viewDidLoad {
+    [super viewDidLoad];
+
+    CGRect applicationFrame = [[UIScreen mainScreen] bounds];
+    logLabel = [[UITextView alloc] initWithFrame:
+        CGRectMake(2.0, 50.0, applicationFrame.size.width - 2.0, applicationFrame.size.height - 50.0)];
+    logLabel.font = [UIFont systemFontOfSize:9.0];
+    logLabel.backgroundColor = [UIColor blackColor];
+    logLabel.textColor = [UIColor greenColor];
+    logLabel.scrollEnabled = YES;
+    logLabel.alwaysBounceVertical = YES;
+#ifndef TARGET_OS_TV
+    logLabel.editable = NO;
+#endif
+    logLabel.clipsToBounds = YES;
+
+    summaryLabel = [[UILabel alloc] initWithFrame: CGRectMake(10.0, 0.0, applicationFrame.size.width - 10.0, 50)];
+    summaryLabel.textColor = [UIColor whiteColor];
+    summaryLabel.font = [UIFont boldSystemFontOfSize: 12];
+    summaryLabel.numberOfLines = 2;
+    summaryLabel.textAlignment = NSTextAlignmentLeft;
+#if !TARGET_OS_SIMULATOR || FORCE_AOT
+    summaryLabel.text = @"Loading...";
+#else
+    summaryLabel.text = @"Jitting...";
+#endif
+    [self.view addSubview:logLabel];
+    [self.view addSubview:summaryLabel];
+
+    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+        void *del = dlsym (RTLD_DEFAULT, "exposed_managed_method");
+        NSAssert(del != NULL, @"'exposed_managed_method' not found");
+        mono_ios_runtime_init ();
+    });
+}
+
+@end
+
+// called from C#
+void
+invoke_external_native_api (void (*callback)(void))
+{
+    if (callback)
+        callback();
+}
+
+// can be called from C# to update UI
+void
+mono_ios_set_summary (const char* value)
+{
+    NSString* nsstr = [NSString stringWithUTF8String:value];
+    dispatch_async(dispatch_get_main_queue(), ^{
+        summaryLabel.text = nsstr;
+    });
+}
+
+// can be called from C# to update UI
+void
+mono_ios_append_output (const char* value)
+{
+    NSString* nsstr = [NSString stringWithUTF8String:value];
+    dispatch_async(dispatch_get_main_queue(), ^{
+        logLabel.text = [logLabel.text stringByAppendingString:nsstr];
+        CGRect caretRect = [logLabel caretRectForPosition:logLabel.endOfDocument];
+        [logLabel scrollRectToVisible:caretRect animated:NO];
+        [logLabel setScrollEnabled:NO];
+        [logLabel setScrollEnabled:YES];
+    });
+}
+
+int main(int argc, char * argv[]) {
+    @autoreleasepool {
+        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
+    }
+}