Linker Command Failed with exit code 1 (Use -v to see invocation) iOS Error

Question

In my application I'm using a static library named ABC.a in that library in a c file named Layout.c there is a function called init(). And I linked the library to the projects and added the .h file. The program is compiled without error but while linking the function its throwing the error. Why?

Info: I've added that static library in build phases also.

And the library is built for armv7, armv7s and arm64. bitcode enabled: No and Build active architectures : NO

Example error:

Undefined symbols for architecture arm64: "AMID_INIT(int*, int*, int)", referenced from: -[ViewController microphone:hasAudioReceived:withBufferSize:withNumberOfChannels:] in Test_lto.o "amid_Val(float const*, int, int*, int, unsigned int)", referenced from: -[ViewController microphone:hasAudioReceived:withBufferSize:withNumberOfChannels:] in Test_lto.o

Please help two days gone for this.

At a guess, the headers for the library don't have C++ guards and you're using them in an objective-C++ program. try wrapping the #import 'lib.h' in an extern "C" {\n#import 'lib.h'\n} to see if that helps things. — Anya Shenanigans
– Anya Shenanigans, Commented May 23, 2017 at 8:28
try this : If your Architectures and Valid Architectures are all right, you may check whether you have add $(inherited) to Other Linker Flags. — KKRocks
– KKRocks, Commented May 23, 2017 at 8:33
@Petesh Your comment is absolutely correct. Awesome man. You saved a lot of my time. Thanks. Put an answer I will check it up. — AMI amitekh
– AMI amitekh, Commented May 23, 2017 at 9:12

Anya Shenanigans · Accepted Answer · 2017-05-23 14:22:03Z

This is based on the fact that you mention that the .a file is generated from a c file. The linker error:

 "AMID_INIT(int*, int*, int)", referenced from: -[ViewController microphone:hasAudioReceived:withBufferSize:withNumberOfChannels:] in Test_lto.o

indicates that the AMID_INIT definition came from a C++/Objective-C++ file - this is because C files would not have information about the parameters of the routine.

From this I was able to surmise that the library header file did not have c++ guards.

Three approaches in this case - wrap all imports of the library header file in the C++ code with something like:

extern "C" { #import "lib.h" }

or create a lib.hpp file, containing:

#pragma once extern "C" { #import "lib.h" }

and #import 'lib.hpp' instead, or fix the lib.h file by adding the standard name mangling preventative:

… near start of lib.h:

#ifdef __cplusplus extern "C" { #endif

… near end of lib.h:

#ifdef __cplusplus } #endif

This allows you to keep using the lib.h with both C and C++ compilers by declaring that all the routines offered by lib.h are exposed using C linkage, rather than C++ linkage.

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