“初始化器不是编译时间常数".错误在.mm中起作用? [英] "Initializer is not a compile time constant" error works in .mm?

问题描述

我对正在观察的情况感到困惑，并希望获得一些见识.首先，我使用Xcode 5，并将LLVM 5编译器选项设置为默认值.

I'm puzzled by a situation I'm observing and would love some insight. First, I'm using Xcode 5, with LLVM 5 compiler options set to defaults.

.m文件中有一行，例如:

I have a line in a .m file such as:

static NSArray * const kSchemaVersions = @[@"1"];

而且，正如预期的那样，我看到一个编译器错误，提示Initializer element is not a compile-time constant.

And, as expected, I see a compiler error saying Initializer element is not a compile-time constant.

但是，如果我将同一行放在.mm(Objective C ++)文件中，则编译器不会抱怨.

However, if I place this same line in a .mm (Objective C++) file, the compiler does not complain.

我完全理解为什么它不应该工作，但是我对为什么它看起来困惑不解.

I completely understand why it shouldn't work, but I'm baffled as to why it appears to.

有想法吗?

推荐答案

正如您提到的，在C和Objective-C中，静态变量只能使用编译时常量进行初始化.另一方面，在C ++(因此是Objective-C ++)中，在运行main之前，在运行时分配了静态变量.

As you mentioned, in C and Objective-C static variables can only be initialised with compile-time constants. In C++ (and therefore Objective-C++) on the other hand, static variables are assigned at run time, before main runs.

有关更多详细信息，请参阅Eli Bendersky的 C和C ++中的非常数全局初始化

For more details have a look at Eli Bendersky's Non-constant global initialization in C and C++

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