Xcode / Cocoa : What are the differences between debug and release builds

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What are the differences between debug and release builds for a Cocoa application?
I know the debug version contains additional information for debugging but what else is different?

Best Answer

Debug builds will contain debugging symbols which can be used by a debugger. Release builds often do not contain debugging symbols, so if you get a crash dump, all you'll get are a bunch of hexadecimal addresses instead of useful symbol names.

Debug builds are not compiled with optimization (-O0 with gcc), whereas release builds are compiled with optimization (typically -O2 or -O3). Optimization makes debugging much, much harder. If you attempt to debug a release application, the debugger will get very confused, since assembly statements no longer match up with HLL statements, statements get reordered, functions get inlined, loops get unrolled, etc.

Debug and release builds also defined different preprocessor symbols, and some code is conditionally compiled based on those (for example, array bounds checks, assertions, etc.), although that is highly application-dependent. A typical example would be to #define NDEBUG for release mode, which causes assertions to be removed.

Related Solutions

Ios – Constants in Objective-C

You should create a header file like

// Constants.h
FOUNDATION_EXPORT NSString *const MyFirstConstant;
FOUNDATION_EXPORT NSString *const MySecondConstant;
//etc.

(you can use extern instead of FOUNDATION_EXPORT if your code will not be used in mixed C/C++ environments or on other platforms)

You can include this file in each file that uses the constants or in the pre-compiled header for the project.

You define these constants in a .m file like

// Constants.m
NSString *const MyFirstConstant = @"FirstConstant";
NSString *const MySecondConstant = @"SecondConstant";

Constants.m should be added to your application/framework's target so that it is linked in to the final product.

The advantage of using string constants instead of #define'd constants is that you can test for equality using pointer comparison (stringInstance == MyFirstConstant) which is much faster than string comparison ([stringInstance isEqualToString:MyFirstConstant]) (and easier to read, IMO).

Ios – How to check for an active Internet connection on iOS or macOS

Important: This check should always be performed asynchronously. The majority of answers below are synchronous so be careful otherwise you'll freeze up your app.

Swift

Install via CocoaPods or Carthage: https://github.com/ashleymills/Reachability.swift

Test reachability via closures

let reachability = Reachability()!

reachability.whenReachable = { reachability in
    if reachability.connection == .wifi {
        print("Reachable via WiFi")
    } else {
        print("Reachable via Cellular")
    }
}

reachability.whenUnreachable = { _ in
    print("Not reachable")
}

do {
    try reachability.startNotifier()
} catch {
    print("Unable to start notifier")
}

Objective-C

Add SystemConfiguration framework to the project but don't worry about including it anywhere
Add Tony Million's version of Reachability.h and Reachability.m to the project (found here: https://github.com/tonymillion/Reachability)

Update the interface section

#import "Reachability.h"

// Add this to the interface in the .m file of your view controller
@interface MyViewController ()
{
    Reachability *internetReachableFoo;
}
@end

Then implement this method in the .m file of your view controller which you can call

// Checks if we have an internet connection or not
- (void)testInternetConnection
{
    internetReachableFoo = [Reachability reachabilityWithHostname:@"www.google.com"];

    // Internet is reachable
    internetReachableFoo.reachableBlock = ^(Reachability*reach)
    {
        // Update the UI on the main thread
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"Yayyy, we have the interwebs!");
        });
    };

    // Internet is not reachable
    internetReachableFoo.unreachableBlock = ^(Reachability*reach)
    {
        // Update the UI on the main thread
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"Someone broke the internet :(");
        });
    };

    [internetReachableFoo startNotifier];
}

Important Note: The Reachability class is one of the most used classes in projects so you might run into naming conflicts with other projects. If this happens, you'll have to rename one of the pairs of Reachability.h and Reachability.m files to something else to resolve the issue.

Note: The domain you use doesn't matter. It's just testing for a gateway to any domain.