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Editorial Team
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Asked: 2026-06-12T22:24:31+00:00

I don’t think I’m giving any Apple secrets away here, so I’ll ask. My

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I don’t think I’m giving any Apple secrets away here, so I’ll ask.
My .pch file looks like this:

#ifndef __IPHONE_4_0
#warning "This project uses features only available in iOS SDK 4.0 and later."
#endif

#ifdef __OBJC__
    #import <Foundation/Foundation.h>
    #import <Availability.h> 
    #import <UIKit/UIKit.h>
    #import "DejaViewAppDelegate.h"
#endif

So, a warning appears on line 2 that says “This project uses features only available in iOS SDK 4.0 and later.”.

The SDK warning is echoing the ifndef warning when #import Availability.h comes AFTER the ifndef statement.
It does NOT throw a warning when the #import Availability.h BEFORE the idndef.

Any reason why?

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1 Answer

  1. Editorial Team

    In the standard project template, <Availability.h> is the first import. That makes sense because that’s where __IPHONE_4_0 is defined.

    The macro at the top checks if IPHONE_4_0 is defined and issues a compiler warning if it’s not. As the macro is defined later (by importing <Availability.h>, you see the compiler warning.

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