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Xcode的Architectures和Valid Architectures的区别

Architectures

这代表，在这个项目里你想要Xcode编译的目标设备列表。

Valid Architectures

还不是太明确这个设置的意图，但是一般来说是不需要更改的。

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在Xcode5.0里的Valid Architectures 设置里，有2个选项：

1. 默认为standard architectures (including 64-bit)(armv7,armv7s,arm64)，这样设置，你的Deployment target最低只能设置为 6.0,(在Xcode5.0.1 之后,最低能够兼容IOS 5.1.1);
2. standard architectures (armv7,armv7s)，这样设置，你的Deployment target最低能设置为 4.3；

原因解释如下：

使用standard architectures (including 64-bit)(armv7,armv7s,arm64)参数， 
则打的包里面有32位、64位两份代码， 
在iPhone5s（iPhone5s的cpu是64位的）下，会首选运行64位代码包， 
其余的iPhone（其余iPhone都是32位的,iPhone5c也是32位）， 
只能运行32位包， 
但是包含两种架构的代码包，只有运行在ios6，ios7系统上。 
这也就是说，这种打包方式，对手机几乎没啥要求，但是对系统有要求，即ios6以上。

而使用standard architectures (armv7,armv7s)参数， 
则打的包里只有32位代码， 
iPhone5s的cpu是64位，但是可以兼容32位代码，即可以运行32位代码。但是这会降低iPhone5s的性能，原因下面的参考有解释。 
其余的iPhone对32位代码包更没问题， 
而32位代码包，对系统也几乎也没什么限制。

所以总结如下： 
要发挥iPhone5s的64位性能，就要包含64位包，那么系统最低要求为ios6。 
如果要兼容ios5以及更低的系统，只能打32位的包，系统都能通用，但是会丧失iPhone5s的性能。

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参考1：

所有IOS设备详情列表 List of iOS devices - Wikipedia, the free encyclopedia

armv6：iPhone 2G/3G，iPod 1G/2G 
armv7：iPhone 3GS/4/4s，iPod 3G/4G，iPad 1G/2G/3G ,iPad Mini 1 
armv7s：iPhone5 ,iPhone5C ,iPad4 
armv8：iPhone5S ,iPad5(iPad Air), iPad Mini 2(iPad Mini Retina)

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参考2：

iOS 7: 如何为iPhone 5S编译64位应用。

Xcode 5编译的iOS 7程序包含了32位和64位两套二进制代码，在32位的iOS系统上会调用32位的二进制代码，在64位系统上会调用64位的二进制代码，以此来解决向后兼容的问题。

同时，考虑到很多32位的程序可能在没有重新编译的情况下部署到64位系统上，64位的iOS系统中带有两套FrameWork，一套是32位的，一套是64位的。 
当64位的iOS系统运行原来的32位程序时，系统会调用32位的FrameWork作为底层支撑，当系统运行64位程序时，系统会调用64位的FrameWork作为底层支撑。

也就是说，当一个iPhone 5S上同时运行32位程序和64位程序时，系统同时将32位和64位两套FrameWork载入了内存中，所以消耗的内存也比较多。

如果一台64位的iOS设备上运行的所有程序都是为64位系统编译过的，iOS系统将只载入64位的FrameWork，这将节省好多内存。所以，如果大家都可以快速将程序传换成64位的，iOS将跑得更快。真的是“大家好才是真的好”。

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参考3：

What's the difference between “Architectures” and “Valid Architectures” in Xcode Build Settings?

Architectures are the ones you want to build, valid architectures are the ones you could conceive of building with your codebase.

So maybe you only want to build your binary for armv7s, but the same source code would compile fine for armv7 and armv6. So VALID_ARCHS = armv6 armv7 armv7s, but you set ARCHS = armv7s because that's all you actually want to build with your code.

Or, in Apple-ese:

ARCHS (Architectures)

Space-separated list of identifiers. Specifies the architectures (ABIs, processor models) to which the binary is targeted. When this build setting specifies more than one architecture, the generated binary may contain object code for each of the specified architectures.

and:

VALID_ARCHS (Valid Architectures)

Space-separated list of identifiers. Specifies the architectures for which the binary may be built. During the build, this list is intersected with the value of ARCHS build setting; the resulting list specifies the architectures the binary can run on. If the resulting architecture list is empty, the target generates no binary.

Source: Xcode Build Setting Reference

In practice, you leave VALID_ARCHS alone and don't worry about changing it, and just fiddle with ARCHSto set the architectures you want to build. Typically, you set a Debug build to just NATIVE_ARCH, since you only want to build the debug version for the machine you'll be testing/running it on, and Release builds for the full spectrum of architectures you plan to support.

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参考4：

Xcode 5 and iOS 7: Architecture and Valid architectures

Set the architecture in build setting to Standard architectures(armv7,armv7s)

iPhone 5S is powered by A7 64bit processor. From apple docs

Xcode can build your app with both 32-bit and 64-bit binaries included. This combined binary requires a minimum deployment target of iOS 7 or later.

Note: A future version of Xcode will let you create a single app that supports the 32-bit runtime on iOS 6 and later, and that supports the 64-bit runtime on iOS 7.

From the documentation what i understood is

• Xcode can create both 64bit 32bit binaries for a single app but the 
  deployment target should be iOS7. They are saying in future it will 
  be iOS 6.0
• 32 bit binary will work fine in iPhone 5S(64 bit processor).

Update (Xcode 5.0.1) 
In Xcode 5.0.1 they added the support to create 64 bit binary for iOS 5.1.1 onwards.

Xcode 5.0.1 can build your app with both 32-bit and 64-bit binaries included. This combined binary requires a minimum deployment target of iOS 5.1.1 or later. The 64-bit binary runs only on 64-bit devices running iOS 7.0.3 and later.

Update (Xcode 5.1) 
Xcode 5.1 made significant change in the architecture section. This answer will be a followup for you. 
Check this

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参考5：

how to stop xcode5.1 building for 64bit

OP is posted the solution along with the question itself. But I feel it would be better to add it as an answer. In Xcode 5.1 apple made significant changes to the architecture section. They made arm64 as part of Standard architectures. That means the projects using the default setting will be automatically build for arm64 also. So what you will do if your app does not support arm64?.

Doc says:

Projects not able to support 64-bit need to specifically set the architectures build setting to not include 64-bit.

How to do that?

1. Goto Targets–>Build Settings–>Architectures–>Architectures

2. Double click on the architecture will popup a menu. Choose others

   

3. Delete the existing row - $(ARCH_STANDARD). Add the required architectures one by one

   

4. Now your architecture section will look like this

   

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参考6：

1. Xcode Build Setting Reference (苹果官方文档)

2. 64-Bit transition Guide for Cocoa Touch (苹果官方文档)

3. Xcode设置项之Architectures和Valid Architectures