Objective-C++ 导入 C++ 类失败，未找到 cassert [英] Objective-C++ importing C++ class fails, cassert not found

问题描述

所以我想在我的 cocos2d + box2d 项目中公开一个 Box2D (C++) 指向其他 Objective-C++ 类的指针.我在我的接口中声明了一个方法getWorld"，它引用了 C++ 类 b2World 并导入了 Box2D.h.我项目中的所有文件都是 .mm 扩展名，我得到以下编译错误:

So I want to publicly expose a Box2D (C++) pointer to other Objective-C++ classes in my cocos2d + box2d project. I declare a method "getWorld" in my interface which references C++ class b2World and imports Box2D.h. All the files in my project are .mm extension, and I get the following compile error:

In file included from DebugDrawLayer.mm:2:
In file included from World.h:10:
In file included from external/Box2d/Box2D/Box2D.h:34:
external/Box2d/Box2D/Common/b2Settings.h:22:10: fatal error: 'cassert' file not found
#include <cassert>

我猜 Box2D.h 不知何故被编译为 C 而不是 C++，但我不明白这是怎么发生的.根据日志，包含链显然是从 .mm 文件开始的.

I guess Box2D.h is somehow compiled as C instead of C++, but I fail to understand how this happens. According to the log the include chain clearly starts from a .mm file.

更新:

日志显示 World.mm(之前编译)清楚地编译为 Objective-c++

The log says for World.mm (compiled earlier) that it clearly compiles as objective-c++

CompileC Objects-normal/i386/World.o World.mm normal i386 objective-c++ com.apple.compilers.llvm.clang.1_0.compiler 

但是对于 DebugDrawLayer.mm 它说的是objective-c

but for DebugDrawLayer.mm it says objective-c

CompileC Objects-normal/i386/DebugDrawLayer.o DebugDrawLayer.mm normal i386 objective-c com.apple.compilers.llvm.clang.1_0.compiler

这两个文件都设置为默认值 - Objective-C++ 源代码.什么给了..?

Both files are set as default - Objective-C++ source. What gives..?

推荐答案

这似乎是 Xcode4 中的一个主要错误，与编译器设置无关 - 只是 Xcode 内部.

This appears to be a MAJOR bug in Xcode4, nothing to do with compiler settings - just Xcode internals.

更新:

我最终找到了根本原因.是的，这是 Xcode/LLVM 中的一个错误.它以错误的顺序编译文件，然后覆盖自己的设置，并自行中断.苹果的技术支持太无能，甚至无法理解这个问题，所以我怀疑他们很快就会修复这个错误.

I eventually found the root cause. Yes, it's a bug in Xcode/LLVM. It compiles files in the wrong order, and then overrides its own settings, and breaks itself. Apple's tech support was too incompetent to even understand the problem, so I doubt they'll be fixing the bug anytime soon.

(注意:跳过此部分，并在下面查看我的原始答案，这给出了一个蛮力但非常快速的解决方案)

(NB: Skip this section, and see below, for my original answer, that gives a BRUTE FORCE but VERY QUICK TO DO solution)

会发生什么......如果编译器看到"一个 C++ 头文件在处理一个 C 类......然后它(内部)将该头文件标记为C"(即使这是几乎不可能).

What happens is ... if the compiler "sees" a C++ header while processing a C class ... it then marks that header (internally) as "C" (even when this is literally impossible).

稍后，当它回到那个头文件，尝试用 C++ 编译它时，它发现它已经告诉自己头文件是C"(因为它非常愚蠢)......并且立即崩溃.

Later on, when it comes back to that header, trying to compile it with C++, it finds it has already told-itself that the header is "C" (because it's incredibly stupid) ... and promptly crashes.

正确解决方案(需要大量时间和精力)是检查项目中的每个 C 文件，并检查(手动，因为 Xcode 很烂)对每个头文件的每个引用 --并且，对于每一个，它导入的每个头文件......等等.

The correct solution (which requires lots of time and effort) is to go through EVERY C FILE in your project, and check (manually, because Xcode sucks) EVERY reference to EVERY header file -- and, for each one, EVERY header file it imports ... etc.

(这可能需要几个小时)

(this can take hours)

...直到找到导致 C 文件看到"C++ 标头的导入链.

...until you find the chain of imports that leads to a C file "seeing" a C++ header.

所有这些都应该是自动化的(但不是).并且根本问题不应该发生(如果 Xcode 编写正确的话).

All of this should be automated (but isn't). And the root problem shouldn't happen (if Xcode were correctly written).

我尝试了网络上其他地方列出的所有方法，大多数解决方案都是不断删除/添加文件，如果幸运的话，Xcode 最终会自行修复".

I tried everything listed elsewhere on the web, most of the solutions are "keep removing/adding the file, and eventually Xcode will fix itself if you're lucky".

我不走运.唯一有效的是:

I wasn't lucky. The only thing that worked was:

1. 转到为您的项目构建设置
2. 找到将源编译为"设置
3. 将其设置为Objective-C++"
4. 重新构建

实际的名称/值是:GCC_INPUT_FILETYPE = sourcecode.cpp.objcpp" - 所以我的猜测是这回避了 Xcode(坏了！)的内部逻辑.

The actual name/value is: "GCC_INPUT_FILETYPE = sourcecode.cpp.objcpp" - so my guess is that this sidesteps Xcode's (broken!) internal logic.

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