How to Assign specific compiler flags to specific files

I recently needed to add an ARC file to a non-arc enabled project.  There were compiler warnings saying the -fobjc-arc flag needed to be added for the file.  To do this in Xcode go to Targets -> Build Phases -> Compiler Sources.  Then find the file and add the flag.

http://stackoverflow.com/questions/8768176/how-to-add-arc-for-specific-file

"_crypto_sign_ed25519_ref_double_scalarmult_vartime", referenced from:

While trying to build Chartboost v4.1 I get the following error:
"_crypto_sign_ed25519_ref_double_scalarmult_vartime", referenced from:
...
...

This seems to be a problem with Chartboost's latest build.

http://forums.xamarin.com/discussion/13953/linker-error-using-chartboost-binding

Cannot compile when including Google Analytics

The linker complains it can't find the following:

_llvm_gcda_emit_arcs

_llvm_gcda_emit_function

_llvm_gcda_end_file

_llvm_gcda_increment_indirect_counter

_llvm_gcda_start_file

Under the target build setting (be sure to select all)

Set:

• Apple LLVM complier
  • Instrument Program Flow: YES
  • Generate Test Coverage Files: YES

http://stackoverflow.com/questions/12670204/ios-code-coverage-broken-in-xcode-4-5

Unknown class in Interface Builder file

This error can show up when using Storyboard or Interface Builder.  The problem is that no actual code references so the linker optimizes the class out of existence.  One solution to select the .m of the class that is giving you trouble.  Then show the file inspector (View->Utilities->Show file inspector) and check your target under the Target Membership section.

More info here:
http://stackoverflow.com/questions/1725881/unknown-class-myclass-in-interface-builder-file-error-at-runtime

Building Error - don't know how to convert instruction

don't know how to convert instruction ea000002 referencing ....


If you are using Xcode 3.2.5 you may be experiencing this error because your architecture has armv7.  Remove armv7 from the "Architectures" and "Valid Architectures" and this error should go away.

Xcode 4 and Xcode 3 compiler differences

The default compiler in Xcode 4 is LLVM GCC 4.2 while the default compiler in Xcode 3 is GCC 4.2.  Why the difference?  LLVM is supposedly faster than GCC and LLVM GCC has the benefits of LLVM and still compatible with GCC.  See more at this great article:

http://useyourloaf.com/blog/2011/3/21/compiler-options-in-xcode-gcc-or-llvm.html

-libxml2 Library not found

One of the 3rd party solutions we have says to add -libxml2 linker flag, but this causes an error when trying to build with xcode.  Googling this error results in someone with a similar problem.  He fixed it by reverting his project file.  His linker flags show -lxml2 instad of -libxml2.  Using -lxml2 works.

http://stackoverflow.com/questions/6173766/iphone-libxml2-not-found-during-build

What is NoThumb in Google Analytics?

Basically, Thumb is an instruction set.  Similar to how ARM is an instruction set.  In the iOS programming guide it says:
“iPhones and iPod touches support two instruction sets, ARM and Thumb. Xcode uses Thumb instructions by default because using Thumb typically reduces code size by about 35 percent relative to ARM.
Applications that have extensive floating point code might perform better if they use ARM instructions rather than Thumb. You can turn off Thumb for your application by turning off the Compile for Thumb build setting.”


Some frameworks require that you use ARM so this is why the NoThumb version of Google Analytics was in high demand.  (An example of this is: http://www.cocos2d-iphone.org/archives/26)

'TheClassName' may not respond to '-methodName:forKey:withType'

// file.m

- (void)methodName:(id)value forKey:(NSString*)key {

[self methodName:value forKey:key withType:A_TYPE];

}

- (void)methodName:(id)value forKey:(NSString*)key withType:(TYPES)type {

....

}

The above lines will show a warning similar to 'TheClassName' may not respond to '-methodName:forkey:withType'. This is because of the order that the methods are written. When the compiler encounters the first method it flags it because the second method has not yet been defined. Reorder the methods to avoid this annoying warning.

source: http://www.goodbyehelicopter.com/?p=257

Another reason this warning message might show is because the method actually is not defined or cannot be found in the interface file. I had the above method declared in a protocol, not the actual interface file. I imported the protocol, but forgot to tell the class to use the protocol ( i didn't say "@interface TheClassName <TheProtocolName> "). I found this out by doing a right-click -> Jump to Definition. And it gave me two options (one in the protocol and one in the class) instead of just going to the Protocol's declaration.