Linker Errors About Non-Existent Functions?

Question

Linker Errors About Non-Existent Functions?

Osman Zakir 101

I have linker errors about functions don't even exist. I have no idea what's going on here. Code is in this GitHub repo.

I have these linker errors:

1>sort.ixx.obj : error LNK2019: unresolved external symbol "void __cdecl words::swap(class std::vector<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >,class std::allocator<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > > &,unsigned __int64,unsigned __int64)" (?swap@Godherald"Words".CosmicTraveler @@YAXAEAV?$vector@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@V?$allocator@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@@2@@std@@_K1@Z::<!words>) referenced in function "void __cdecl words::sort(class std::vector<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >,class std::allocator<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > > &,unsigned __int64,unsigned __int64)" (?sort@Godherald"Words".CosmicTraveler @@YAXAEAV?$vector@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@V?$allocator@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@@2@@std@@_K1@Z::<!words>)
1>utils.ixx.obj : error LNK2019: unresolved external symbol "unsigned __int64 __cdecl words::max_word_length(class std::vector<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >,class std::allocator<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > > const &)" (?max_word_length@Godherald"Words".CosmicTraveler @@YA_KAEBV?$vector@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@V?$allocator@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@@2@@std@@@Z::<!words>) referenced in function "void __cdecl words::show_words(class std::vector<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > >,class std::allocator<class std::shared_ptr<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > > > > const &)" (?show_words@Godherald"Words".CosmicTraveler @@YAXAEBV?$vector@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@V?$allocator@V?$shared_ptr@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@std@@@2@@std@@@Z::<!words>)
1>E:\programming\visual_studio_2019\Projects\beginningcpp20\chapter11ex5\x64\Debug\chapter11ex5.exe : fatal error LNK1120: 2 unresolved externals

I created an empty project and added the code to it. Would someone please help me with these errors? Thanks.

Edit for clarification and some more info: I'm using VS Community 2022.

And the functions words::max_word_length and words::swap weren't declared anywhere, since the functions I declared with those names are actually declared outside the words namespace rather than inside. The stupid thing is trying to look for definitions of functions that aren't even declared anywhere, hence me saying I have linker errors about functions that don't exist. I hope that clears things up.

Answer 1

Minxin Yu 3,936 Microsoft Vendor

Hi, @Osman Zakir

internals.cpp add module words:sort; in the first line.

Best regards,

Minxin Yu

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Osman Zakir 101 Reputation points

2022-01-24T08:44:11.787+00:00

Thanks for the reply.

I added module words; (because internals.cpp defines functions from both partitions (sort and utils)) and tried to build it again but still have those same linker errors.

Minxin Yu 3,936 Microsoft Vendor

This is the snippet I modified for your reference. It is not a good idea to put two function definitions from different modules into one cpp file.
internals.cpp:

module words:sort;  
import words;  
  
import <iostream>;  
  
std::size_t max_word_length(const words::Words& words)  
{  
	std::size_t max{};  
	for (auto& pword : words)  
	{  
		if (max < pword->length())  
		{  
			max = pword->length();  
		}  
	}  
	return max;  
}  
  
void swap(words::Words& words, std::size_t first, std::size_t second)  
{  
	auto temp{ words[first] };  
	words[first] = words[second];  
	words[second] = temp;  
}

Osman Zakir 101 Reputation points

2022-01-25T11:03:29.52+00:00

Why do we need to put both import words:sort; and import words;? And also, again, why are there linker errors about words::max_word_length and words::swap which are functions that weren't even declared?
Osman Zakir 101 Reputation points

2022-01-25T11:06:36.17+00:00

Also, they're functions defined in implementation files for interface partitions of the same module.

The original exercise asks to create a module implementation partition called internals. But it doesn't seem like it's possible to do that.
Minxin Yu 3,936 Reputation points Microsoft Vendor

2022-01-26T01:56:07.037+00:00

linker errors: the compiler did not find the relevant module implementation unit module words:sort; or module words:utils; (not import words:sort;).
export import :alias uesd in two ixx files, module words:sort; can also be changed to module words:alias;.
Since it involves the implementation principle of the module, I suggest you post a new issue on the Q&A platform.
Minxin Yu 3,936 Reputation points Microsoft Vendor

2022-01-31T01:17:56.1+00:00

Hi, @Osman Zakir
May I know if your code can be complied well now?

Linker Errors About Non-Existent Functions?

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