将源文件扩展名从 .m 更改为 .mm 在屏幕保护程序项目的 Xcode 9.3 中失败

Question

今天我决定要使用 Xcode 为我的 mac 编写一个屏幕保护程序，并希望在 C++ 中完成大部分繁重的工作。根据我之前混合使用 C++ 和 Objective-C++ 的经验，当您想在其中合并一些 C++ 时，只需将 .m 源文件的扩展名更改为 .mm。

不过，我运行遇到了一个烦人的问题。如果我制作了一个 Xcode 屏幕保护程序项目，除了将初始 TestScreenSaverView.m 文件重命名为 TestScreenSaverView.mm 之外什么都不做，屏幕保护程序从编译和链接正常到编译和链接有问题。请注意，除了更改文件的扩展名外，我没有添加任何新代码。这是日志输出：

Showing Recent Issues
Check dependencies

Write auxiliary files

write-file /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver.hmap
write-file /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-generated-files.hmap
write-file /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-all-target-headers.hmap
write-file /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-own-target-headers.hmap
write-file /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-project-headers.hmap
write-file /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-all-non-framework-target-headers.hmap
/bin/mkdir -p /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64
write-file /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaver.LinkFileList

Create product structure

/bin/mkdir -p /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug/TestScreensaver.saver/Contents
/bin/mkdir -p /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug/TestScreensaver.saver/Contents/MacOS

ProcessInfoPlistFile /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug/TestScreensaver.saver/Contents/Info.plist TestScreensaver/Info.plist
    cd /Users/cjh/Documents/code/swift/TestScreensaver
    builtin-infoPlistUtility /Users/cjh/Documents/code/swift/TestScreensaver/TestScreensaver/Info.plist -expandbuildsettings -platform macosx -o /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug/TestScreensaver.saver/Contents/Info.plist

CompileC /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaverView.o TestScreensaver/TestScreensaverView.mm normal x86_64 objective-c++ com.apple.compilers.llvm.clang.1_0.compiler
    cd /Users/cjh/Documents/code/swift/TestScreensaver
    export LANG=en_US.US-ASCII
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -x objective-c++ -arch x86_64 -fmessage-length=0 -fdiagnostics-show-note-include-stack -fmacro-backtrace-limit=0 -std=gnu++14 -stdlib=libc++ -fobjc-arc -fobjc-weak -fmodules -gmodules -fmodules-cache-path=/Users/cjh/Library/Developer/Xcode/DerivedData/ModuleCache.noindex -fmodules-prune-interval=86400 -fmodules-prune-after=345600 -fbuild-session-file=/Users/cjh/Library/Developer/Xcode/DerivedData/ModuleCache.noindex/Session.modulevalidation -fmodules-validate-once-per-build-session -Wnon-modular-include-in-framework-module -Werror=non-modular-include-in-framework-module -Wno-trigraphs -fpascal-strings -O0 -fno-common -Wno-missing-field-initializers -Wno-missing-prototypes -Werror=return-type -Wdocumentation -Wunreachable-code -Wno-implicit-atomic-properties -Werror=deprecated-objc-isa-usage -Werror=objc-root-class -Wno-arc-repeated-use-of-weak -Wimplicit-retain-self -Wno-non-virtual-dtor -Wno-overloaded-virtual -Wno-exit-time-destructors -Wduplicate-method-match -Wno-missing-braces -Wparentheses -Wswitch -Wunused-function -Wno-unused-label -Wno-unused-parameter -Wunused-variable -Wunused-value -Wempty-body -Wuninitialized -Wconditional-uninitialized -Wno-unknown-pragmas -Wno-shadow -Wno-four-char-constants -Wno-conversion -Wconstant-conversion -Wint-conversion -Wbool-conversion -Wenum-conversion -Wno-float-conversion -Wnon-literal-null-conversion -Wobjc-literal-conversion -Wshorten-64-to-32 -Wno-newline-eof -Wno-selector -Wno-strict-selector-match -Wundeclared-selector -Wdeprecated-implementations -Wno-c++11-extensions -DDEBUG=1 -DOBJC_OLD_DISPATCH_PROTOTYPES=0 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -fasm-blocks -fstrict-aliasing -Wprotocol -Wdeprecated-declarations -Winvalid-offsetof -mmacosx-version-min=10.13 -g -fvisibility-inlines-hidden -Wno-sign-conversion -Winfinite-recursion -Wmove -Wcomma -Wblock-capture-autoreleasing -Wstrict-prototypes -Wrange-loop-analysis -Wunguarded-availability -index-store-path /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Index/DataStore -iquote /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-generated-files.hmap -I/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-own-target-headers.hmap -I/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-all-target-headers.hmap -iquote /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/TestScreensaver-project-headers.hmap -I/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug/include -I/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/DerivedSources/x86_64 -I/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/DerivedSources -F/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug -MMD -MT dependencies -MF /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaverView.d --serialize-diagnostics /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaverView.dia -c /Users/cjh/Documents/code/swift/TestScreensaver/TestScreensaver/TestScreensaverView.mm -o /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaverView.o

Ld /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug/TestScreensaver.saver/Contents/MacOS/TestScreensaver normal x86_64
    cd /Users/cjh/Documents/code/swift/TestScreensaver
    export MACOSX_DEPLOYMENT_TARGET=10.13
    /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++ -arch x86_64 -bundle -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -L/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug -F/Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug -filelist /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaver.LinkFileList -mmacosx-version-min=10.13 -Xlinker -object_path_lto -Xlinker /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaver_lto.o -Xlinker -export_dynamic -Xlinker -no_deduplicate -stdlib=libc++ -fobjc-arc -fobjc-link-runtime -ObjC -lc++ -Xlinker -dependency_info -Xlinker /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Intermediates.noindex/TestScreensaver.build/Debug/TestScreensaver.build/Objects-normal/x86_64/TestScreensaver_dependency_info.dat -o /Users/cjh/Library/Developer/Xcode/DerivedData/TestScreensaver-dufowvmnhdeakfekvozrelyhhccq/Build/Products/Debug/TestScreensaver.saver/Contents/MacOS/TestScreensaver

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_ScreenSaverView", referenced from:
      _OBJC_CLASS_$_TestScreensaverView in TestScreensaverView.o
  "_OBJC_METACLASS_$_ScreenSaverView", referenced from:
      _OBJC_METACLASS_$_TestScreensaverView in TestScreensaverView.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)



Activity Log Complete    6/4/18, 2:06 PM

不太确定是什么问题，因为我以前从未遇到过问题。有谁知道可能是什么问题？

为了完整起见，下面是项目初始化的代码：

TestScreensaverView.h

//
//  TestScreensaverView.h
//  TestScreensaver
//
//  Created by C. Howard on 6/4/18.
//  Copyright © 2018 C. Howard. All rights reserved.
//

#import <ScreenSaver/ScreenSaver.h>

@interface TestScreensaverView : ScreenSaverView

@end

TestScreensaverView.mm（原TestScreensaverView.m）

//
//  TestScreensaverView.m
//  TestScreensaver
//
//  Created by C. Howard on 6/4/18.
//  Copyright © 2018 C. Howard. All rights reserved.
//

#import "TestScreensaverView.h"

@implementation TestScreensaverView

- (instancetype)initWithFrame:(NSRect)frame isPreview:(BOOL)isPreview
{
    self = [super initWithFrame:frame isPreview:isPreview];
    if (self) {
        [self setAnimationTimeInterval:1/30.0];
    }
    return self;
}

- (void)startAnimation
{
    [super startAnimation];
}

- (void)stopAnimation
{
    [super stopAnimation];
}

- (void)drawRect:(NSRect)rect
{
    [super drawRect:rect];
}

- (void)animateOneFrame
{
    return;
}

- (BOOL)hasConfigureSheet
{
    return NO;
}

- (NSWindow*)configureSheet
{
    return nil;
}

@end

Answer 1

似乎缺少 Obj-C class ScreenSaverView 的实现，从错误消息中可以明显看出。我在 ld 的命令行中没有看到它，但由于您发布了屏幕截图而不是从日志中复制粘贴，所以我无法搜索它，所以也许我错过了它。

Edit Hokay，让 myself 错过了重点并且一路上对 OP 相当粗鲁，我现在已经到了这个的底部，它很简单。

看来您需要将ScreenSaverView框架添加到您的项目中，您可以按照此处的说明进行操作：

http://docs.onemobilesdk.aol.com/ios-ad-sdk/adding-frameworks-xcode.html

如果您的源文件构建为 .m 不清楚，为什么不需要这样做。你会认为你总是需要它，但显然不是。把它归结为史蒂夫乔布斯的精神，只是在坟墓之外玩弄我们这些凡人。

将源文件扩展名从 .m 更改为 .mm 在屏幕保护程序项目的 Xcode 9.3 中失败

Changing source file extension from .m to .mm failing in Xcode 9.3 for Screen Saver project

c++

objective-c

xcode

objective-c++

screensaver