Xcode gives Apple Mach-O linker error

Question

I just compiled a project and Xcode returns these two errors which don't seem to be my code's fault. How do I fix them?

Undefined symbols for architecture i386:
  "_vImageBoxConvolve_ARGB8888", referenced from:
      -[UIImage(Blur) boxblurImageWithBlur:] in UIImage+Blur.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Kerf

Care to show the related code? – Hluchy

The problem is with the UIImage+Blur.m file. It's looking for a symbol named vImageBoxConvolve_ARGB8888. You need to include the .m (or .c) file that has this symbol. – Idio

Look at these links, they are very similar: #22033487 #20073646 – Romanov

Answer 1

Teaching a man (or women) how to fish:

Usually Mach-O Linker Error means you have not included a header file for a function you are using in your code.

Easiest way is to copy that function or method call and paste into Xcode quick search using shift+command+O. This will search all frameworks (and header files), find that function or method call and show you its location (the header in this case):

In this case, this call belongs to the Accelerate framework so on top of your file, enter:

#import <Accelerate/Accelerate.h>

When doing quick search, you might have to get rid of leading underscore. In other words, search for vImageBoxConvolve_ARGB8888

Hope this helps

Requiem

This isn't accurate. Linker errors of this nature are most frequently due to failing to link against the framework or library that provides a symbol you're using. If you fail to #include or #import the necessary header you're much more likely to get a warning along the lines of warning: implicit declaration of function 'vImageBoxConvolve_ARGB8888' is invalid in C99. Adding the missing #include or #import will address the compiler warning, but does nothing to address the linker error. – Diatomic

This is a good way of finding out which framework you're missing though – Factitious

I can't find out the missing library, can you please tell me how to find out which library is missing. – Jamijamie

Answer 2

Google is your friend: someone else fixed this by adding the Accelerate framework to their project (and this does look like a framework error).

https://github.com/rnystrom/RNBlurModalView/issues/5

Make sure you also have the QuartzCore framework included as well, as that is also required by that library.

Stoeber

It is not necessary to link against QuartzCore to use the Accelerate framework. – Diatomic

I didn't say it was. The library he's using - RNBlurModalView - requires both QuartzCore and Accelerate to function. Chances are good if one was left out, the other was too, so I added it as a note in my answer. – Stoeber

Answer 3

Apparently vImageBoxConvolve_ARGB8888() is not defined. See if the Accelerate framework is properly included in the project.

Chronogram