Question

I have a problem. I get an error and I’m not sure why it’s happening.

2>Home.obj : error LNK2019: unresolved external symbol "**void __cdecl LogAString(char *,...)**" (?LogAString@@YAXPADZZ) referenced in function "**public: static void __cdecl X::Home::HomeStart(void)**" (?HomeStart@Home@X@@SAXXZ)
2>Widget.obj : error LNK2001: unresolved external symbol "void __cdecl LogAString(char *,...)" (?LogAString@@YAXPADZZ)
2>J:\src\out.dll : fatal error LNK1120: 1 unresolved externals

Here’s my code:

Log.h

#pragma once

#include <iostream>
#include <cstdarg>

void LogAString(char* fmt, ...);
void LogAnError(char* fmt, ...);

Log.cpp

#include "Log.h"

#include <Util/String/String Formatting.h> // defines format(). Does not have any errors or issues.

void LogAString(char* fmt, ...)
{
    va_list ap;
    va_start(ap, fmt);
    vprintf(fmt, ap);
    va_end(ap);
};

void LogAnError(char* fmt, ...)
{
    va_list ap;
    va_start(ap, fmt);

    auto formatted_string = format("ERROR: %s", fmt).c_str();
    LogAString(const_cast<char*>(formatted_string), ap);

    va_end(ap);
};

Home.cpp (extract)

#include "Home.h"
#include "Log.h"

namespace X {

void Home::HomeStart()
{
    while (true)
    {
        auto number_of_widgets = Widgets::Count();
        LogAString("Loading with %d widgets", number_of_widgets);
    }
}

} // namespace X

I thought I’ve declared and defined the functions in the header and cpp files respectively. Why am I getting these errors? I’ve been at it for a few hours now, and still not sure why this is happening. Using VC++ on VS 2010.

I’m not using any other external libraries at this point. The compile target is a DLL, “out.dll”.

Answer 1

Did you remember to add Log.cpp to your project?

If so, then open the file log.obj in a hex editor. Search for the string LogAnError. It will be part of a larger decorated string. Use the undname command to undecorate it. Compare it with what the linker cannot resolve. Identify the difference and fix your LogAnError function so they match again.