"pod lib lint" command throws error with mixed objective-c and objective-c++ files

I try to create a simple cocoapods library with objective-c and objective-c++ files. When executing the command pod lib lint I get an error.

Pod structure:

• mypod

  • src

    • // A.h
      #pragma once
      
      #import <Foundation/Foundation.h>
      
      NSString* foo(void);
      NSString* bar(void);
      

    • // A.m
      #import "foo.h"
      #import "bar.h"
      
      NSString* foo() {
        return @"Foo";
      }
      
      NSString* bar() {
        int myInt = getValue();
        return [NSString stringWithFormat:@"%d",myInt];
      }
      
      

    • // B.h
      #pragma once
      
      int getValue(void);
      

    • // B.mm
      #import "bar.h"
      
      int getValue(void)
      {
        return 2;
      }
      

  • mypod.podspec

    Pod::Spec.new do |spec|
        spec.name                     = 'mypod'
        spec.version                  = '1.0'
        spec.homepage                 = 'mypod'
        spec.source                   = { :git => "Not Published", :tag => "Cocoapods/#{spec.name}/#{spec.version}" }
        spec.authors                  = ''
        spec.license                  = ''
        spec.summary                  = 'mypod'
        spec.ios.deployment_target    = '13.5'
        spec.source_files             = 'src/A.h', 'src/A.m', 'src/B.h', 'src/B.mm'
        spec.private_header_files     = 'src/A.h'
        spec.public_header_files      = 'src/B.h'
        spec.library = "c++"
        spec.pod_target_xcconfig      = {
        "OTHER_LDFLAGS" => "-lstdc++",
        'LANG_CXX_LANGUAGE_STANDARD' => 'c++20',
        'CLANG_CXX_LIBRARY' => 'libc++',
        'ARCHS' => 'arm64'
        }
    end
    

Executing the command `pod lib lint --platforms=ios --verbose` on an M1 mac throws an error:

    Undefined symbols for architecture arm64:
      "_getValue", referenced from:
          _bar in foo.o
    ld: symbol(s) not found for architecture arm64
    clang: error: linker command failed with exit code 1 (use -v to see invocation)

    ** BUILD FAILED **

Does somebody know what's the problem?

When importing the sames headers into C++ and Objective-C compilation units, you have to wrap the declarations with extern "C" guards to avoid their names being mangled when linking:

#ifdef __cplusplus
extern "C" {
#endif

int getValue(void);

#ifdef __cplusplus
}
#endif