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

问题描述

所以我想在我的cocos2d + box2d项目中公开一个指向其他Objective-C ++类的Box2D（C ++）指针。我在我的接口中声明一个方法getWorld，引用C ++类b2World并导入Box2D.h。我的项目中的所有文件都是.mm扩展名，并得到以下编译错误：

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>

我想Box2D.h被编译为C而不是C ++，但我不明白发生。根据日志，包含链显然从.mm文件开始。

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：

对于World.mm（早期编译），它清楚地编译为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 

但对于DebugDrawLayer.mm，它表示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 - Objective-C ++源码。

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的内部。

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

UPDATE：

。是的，这是Xcode / LLVM中的一个错误。它以错误的顺序编译文件，然后覆盖其自己的设置，并打破自身。苹果的技术支持太不胜任，甚至不能理解这个问题，所以我怀疑他们很快就会修复这个bug。

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：跳过这一节， ，对于我的原始答案，给予BRUTE FORCE但非常快速做DO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 ++头处理 C类...然后将该标题（内部）标记为C（即使这在字面上是不可能的）。

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).

当它回到那个头，试图用C ++编译它，它发现它已经告诉 - 本身，头是C（因为它是令人难以置信的愚蠢）...并立即崩溃。

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.

正确的解决方案（需要大量的时间和精力）是通过你的项目中的每个C文件，并检查（手动，因为Xcode吸）引用EVERY头文件 - 并为每个头文件导入...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 ++头文件的导入链。

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

应该是自动的（但不是）。而且根本问题不应该发生（如果Xcode正确写入）。

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

，大多数解决方案是保持删除/添加文件，最终Xcode将修复自己，如果你幸运。

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".

我不幸运。唯一的工作是：

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

1. 前往您的专案建立设定


2. Compile Sources Assetting


3. 将其设置为Objective-C ++


4. 重新构建

1. Go to build settings for your project
2. find the "Compile Sources As" setting
3. set it to "Objective-C++"
4. re-build

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的（破碎的）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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