Linker warning causes random linking errors every few compilations - c++

Question

I can't get a minimal reproduceable example any smaller than what I have. Mainly because I can't debug the issue, it seems completely random and I don't consistently get the error, sometimes it compiles, sometimes it doesn't. I have reverted back to when I had the error so I can copy the code, but since then, I haven't gotten an error. Basically, I have no other ideas left other than to fix all my linker warnings. I remember it was mostly related to this warning LNK4042 object specified more than once; extras ignored in main.obj. There is also another warning I don't understand, that being I have the binaries for a library named GLEW, yet statically linking it invokes a linker warning, LNK4099 PDB 'vc120.pdb' was not found with 'glew32s.lib(glew.obj)' or at '\SolutionDir\Debug\vc120.pdb'; linking object as if no debug info
What are the fixes for these warnings? Hopefully to stop me randomly getting errors that, when I change one thing it compiles, and then revert it back and it still compiles.
Here is the code, main.h
#pragma once
#ifndef MAIN_H
#define MAIN_H
#include <GL/glew.h> // Initialize with glewInit()
#ifndef GLFW_INCLUDE_NONE
#define GLFW_INCLUDE_NONE // GLFW including OpenGL headers causes ambiguity or multiple definition errors.
#endif // GLFW_INCLUDE_NONE
#include <GLFW/glfw3.h>
#include "ImGui/imgui.h"
#include "ImGui/implot.h"
#include "ImGui/imgui_impl_glfw.h"
#include "ImGui/imgui_impl_opengl3.h"
#include <iostream> //std::string
class Main ///Singleton
{
public:
Main(const Main&) = delete;
Main(Main&&) = delete;
Main& operator=(const Main&) = delete;
Main& operator=(Main&&) = delete;
private:
Main();
static Main& Get_Instance();
friend int main(int argc, char* argv[]);
static void Mainloop();
static void Init();
static void Free();
GLFWwindow* m_Window = nullptr;
std::string m_GLSL_Version = "";
int m_Window_Width = 1280;
int m_Window_Height = 720;
};
#endif // MAIN_H
and main.cpp
#include "main.h"
Main::Main()
{
}
Main& Main::Get_Instance()
{
static Main instance;
return instance;
}
void Main::Init()
{
// Setup window
Get_Instance(); //Init constructor
if (!glfwInit()) {
std::cout << "Could not initialize GLFW" << std::endl;
std::cin.get();
exit(EXIT_FAILURE);
}
Get_Instance().m_GLSL_Version = "#version 460";
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 6);
// Create window with graphics context
Get_Instance().m_Window = glfwCreateWindow(Get_Instance().m_Window_Width, Get_Instance().m_Window_Height, "Program", NULL, NULL);
if (Get_Instance().m_Window == NULL) {
std::cout << "Could not create GLFW window" << std::endl;
std::cin.get();
exit(EXIT_FAILURE);
}
glfwMakeContextCurrent(Get_Instance().m_Window);
glfwSwapInterval(0); // vsync
if (glewInit() != GLEW_OK)
{
fprintf(stderr, "Failed to initialize OpenGL loader!\n");
std::cin.get();
exit(EXIT_FAILURE);
}
// Setup Dear ImGui context
IMGUI_CHECKVERSION();
ImGui::CreateContext();
ImPlot::CreateContext();
// Setup Dear ImGui style
ImGui::StyleColorsClassic();
// Setup Platform/Renderer backends
ImGui_ImplGlfw_InitForOpenGL(Get_Instance().m_Window, true);
ImGui_ImplOpenGL3_Init(Get_Instance().m_GLSL_Version.c_str());
}
void Main::Mainloop()
{
// Main loop
while (!glfwWindowShouldClose(Get_Instance().m_Window))
{
//Events
glfwPollEvents();
// Start the Dear ImGui frame
ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplGlfw_NewFrame();
ImGui::NewFrame();
ImGui::Text("%.3f", ImGui::GetIO().Framerate);
// Rendering
ImGui::Render();
glfwGetFramebufferSize(Get_Instance().m_Window, &Get_Instance().m_Window_Width, &Get_Instance().m_Window_Height);
glViewport(0, 0, Get_Instance().m_Window_Width, Get_Instance().m_Window_Height);
glClearColor(0.45f, 0.55f, 0.60f, 1.00f);
glClear(GL_COLOR_BUFFER_BIT);
ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
glfwSwapBuffers(Get_Instance().m_Window);
}
}
void Main::Free()
{
// Cleanup
ImGui_ImplOpenGL3_Shutdown();
ImGui_ImplGlfw_Shutdown();
ImPlot::DestroyContext();
ImGui::DestroyContext();
glfwDestroyWindow(Get_Instance().m_Window);
glfwTerminate();
}
int main(int argc, char* argv[])
{
Main::Init();
Main::Mainloop();
Main::Free();
return 0;
}
Edit: It happened again, here are the errors:
Error LNK1561 entry point must be defined
Warning LNK4042 object specified more than once; extras ignored (THIS IS IN MY main.obj file, its the only linker issue that references my actual files, the rest reference either 'LINK' or 'libucrt.lib(something here)'
Error LNK2005 __cexit already defined in ucrtd.lib(ucrtbased.dll)
Error LNK2005 __crt_atexit already defined in ucrtd.lib(ucrtbased.dll)
Error LNK2005 __crt_at_quick_exit already defined in ucrtd.lib(ucrtbased.dll)
Error LNK2005 __execute_onexit_table already defined in ucrtd.lib(ucrtbased.dll)
Error LNK2005 __initialize_narrow_environment already defined in ucrtd.lib(ucrtbased.dll)
Error LNK2005 __initialize_onexit_table already defined in ucrtd.lib(ucrtbased.dll)
Error LNK2005 __register_onexit_function already defined in ucrtd.lib(ucrtbased.dll)
Error LNK2005 __seh_filter_dll already defined in ucrtd.lib(ucrtbased.dll)

Answer 1

Regarding the LNK4042 warning, you may be able to resolve the issue, if you open the properties for the entire project, and the change the value under C/C++ -> Output Files -> "Object File Name" to be the following:
$(IntDir)/%(RelativeDir)/