[MSVC compiler] Cleanup crash when having one OutPin connected with multiple InPin's

[RoBaertschi]

Version: master branch ImGui: 1.90.5-docking

Issue

Connecting a OutPin with 2 or more InPin's and then close the program. The deconstructor from ImFlow::Link produces a "Access violation on reading location ...".

One fix that I tried, was to replace m_left with m_right but that seems to break other things, like the node deletion logic.

Link::~Link() {
-    m_left->deleteLink();
+    m_right->deleteLink();
}

Code

I minimized my code to be still functional and replicate the issue here. It is not the most good looking code, but should be readable enough.

Also, I added all c++ code in the spoilers following.

main.cpp

```c++ #include "Window.h" int main() { CWindow window{}; window.run(); return 0; } ```

Window.h

```c++ #ifndef BOOLEANTABLE_WINDOW_H #define BOOLEANTABLE_WINDOW_H #include #include #include #include #include #include #include const int cWinHeight = 400; const int cWinWidth = 600; class CWindow { SDL_Window* window; SDL_GLContext context; bool running = true; std::shared_ptr imNodeFlow; std::vector variables; public: explicit CWindow(); ~CWindow(); void run(); }; #endif //BOOLEANTABLE_WINDOW_H ```

Window.cpp

```c++ #include "Window.h" #include "nodes/AndNode.h" CWindow::CWindow() : imNodeFlow(std::make_shared("Main Grid")) { if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMEPAD) != 0) { throw std::runtime_error("Could not initialize SDL3"); } SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4); SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5); SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE); SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1"); SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24); SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8); window = SDL_CreateWindow("Boolean Tables", cWinWidth, cWinHeight, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE); if (window == nullptr) { throw std::runtime_error("Could not create a SDL3 Window"); } context = SDL_GL_CreateContext(window); if (context == nullptr) { throw std::runtime_error("Could not create a OpenGL Context"); } SDL_GL_MakeCurrent(window, context); SDL_GL_SetSwapInterval(1); int gl_version = gladLoadGL(SDL_GL_GetProcAddress); if (gl_version == 0) { throw std::runtime_error("Could not initialize OpenGL context"); } IMGUI_CHECKVERSION(); ImGui::CreateContext(); ImGuiIO& io = ImGui::GetIO(); (void)io; io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard; io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad; io.ConfigFlags |= ImGuiConfigFlags_DockingEnable; io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable; ImGui::StyleColorsDark(); // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones. ImGuiStyle& style = ImGui::GetStyle(); if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) { style.WindowRounding = 0.0f; style.Colors[ImGuiCol_WindowBg].w = 1.0f; } // Setup Platform/Renderer backends ImGui_ImplSDL3_InitForOpenGL(window,context); ImGui_ImplOpenGL3_Init(); imNodeFlow->addNode(ImVec2{2, 2}); imNodeFlow->droppedLinkPopUpContent([this](ImFlow::Pin *pin) { if (ImGui::Button("And")) { auto node = this->imNodeFlow->placeNode(); pin->createLink(node->first.get()); } }); } CWindow::~CWindow() { imNodeFlow.reset(); ImGui_ImplOpenGL3_Shutdown(); ImGui_ImplSDL3_Shutdown(); ImGui::DestroyContext(); SDL_GL_DeleteContext(context); SDL_DestroyWindow(window); SDL_Quit(); } void CWindow::run() { ImGuiIO& io = ImGui::GetIO(); (void)io; while(running) { for(SDL_Event event; SDL_PollEvent(&event);) { ImGui_ImplSDL3_ProcessEvent(&event); switch (event.type) { case SDL_EVENT_QUIT: running = false; return; case SDL_EVENT_WINDOW_CLOSE_REQUESTED: if (event.window.windowID == SDL_GetWindowID(window)) { running = false; return; } break; default: break; } } ImGui_ImplOpenGL3_NewFrame(); ImGui_ImplSDL3_NewFrame(); ImGui::NewFrame(); ImGui::Begin("Boolean Editor"); imNodeFlow->update(); ImGui::End(); ImGui::Render(); glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y); glClearColor(0.f, 0.f, 0.f, 1.f); glClear(GL_COLOR_BUFFER_BIT); ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData()); if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable) { SDL_Window* backup_current_window = SDL_GL_GetCurrentWindow(); SDL_GLContext backup_current_context = SDL_GL_GetCurrentContext(); ImGui::UpdatePlatformWindows(); ImGui::RenderPlatformWindowsDefault(); SDL_GL_MakeCurrent(backup_current_window, backup_current_context); } SDL_GL_SwapWindow(window); } } ```

AndNode.h

```c++ #ifndef BOOLEANTABLE_ANDNODE_H #define BOOLEANTABLE_ANDNODE_H #include class CAndNode : public ImFlow::BaseNode { public: std::shared_ptr> first; std::shared_ptr> second; CAndNode(); }; #endif //BOOLEANTABLE_ANDNODE_H ```

AndNode.cpp

```c++ #ifndef BOOLEANTABLE_ANDNODE_H #define BOOLEANTABLE_ANDNODE_H #include class CAndNode : public ImFlow::BaseNode { public: std::shared_ptr> first; std::shared_ptr> second; CAndNode(); }; #endif //BOOLEANTABLE_ANDNODE_H ```

[Fattorino]

Thanks for the detailed issue. I haven't been able to reproduce the issue in the non-docking branch of ImGui, I'll have to try again with docking another day.

Also please note that in this minimal example, the end node will always return true, and it's also not taking advantage of the full potential of getInVal<>()

[RoBaertschi]

I haven't been able to reproduce the issue in the non-docking branch of ImGui, I'll have to try again with docking another day.

That is weird, I just moved to the non docking branch of imgui and that does not change anything. If you want to test that, I created a new branch in the repo. Also I switched to uids, but didn't change anything.

Maybe something is wrong with my setup, but I would not know what.

[RoBaertschi]

I recorded a demo of what is happening here, maybe it could help with understanding what is going wrong.

https://github.com/Fattorino/ImNodeFlow/assets/72601088/d5ba8ade-889b-4e84-b9d1-19b7a230ca48

[RoBaertschi]

So, I did some testing and found something. When I compile the program with MSVC, then it will crash. But with mingw, it does not crash and I don't know why. Also, using LLVM gives another error (These green bars can be ignored, they seem to come from some sort of other issue when taking the screenshot): Maybe this could help, it is probably a MSVC issue.

[eminor1988]

I have encountered the situation recently, too.

I guess the root cause is that ImNodeFlow::m_nodes are destructed in any order when ImNodeFlow is destructing. Therefore, the instance of OutPin will be destructed before the Link.

---

The problem has gone after I added:

ImNodeFlow.h

~ImNodeFlow() { removeLinks(); }

void removeLinks();

ImNodeFlow.cpp

  void ImNodeFlow::removeLinks()
  {
      for (auto& itr : m_nodes) {
          for (auto& inPin : itr.second->getIns()) {
              inPin->deleteLink();
          }
      }
  }

---

Can you please see if this can solve your problem?

[Fattorino]

What compiler are you using?

[eminor1988]

Visual C++ 2022 17.10.3

Compiler: MSVC 19.40.33811.0 on Windows-10.0.19045

[Fattorino]

I've implemented something similar with the latest commit in the dev branch. Could you check if it works?

[eminor1988]

I tested it. The problem is still there.

---

The callstack:

---

I consider that because Link::m_left (OutPin) is already destructed with ~BaseNode() before the Link destructing.