SIGSEGV when calling OpenGL function from DLL #8406
Description
Version/Branch of Dear ImGui:
master
Back-ends:
imgui_impl_sdl2.cpp + imgui_impl_opengl3.cpp
Compiler, OS:
Linux + clang 19.1.7
Full config/build information:
Dear ImGui 1.91.9 WIP (19184)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201703
define: __linux__
define: __GNUC__=4
define: __clang_version__=19.1.7
--------------------------------
io.BackendPlatformName: imgui_impl_sdl2
io.BackendRendererName: imgui_impl_opengl3
io.ConfigFlags: 0x00000003
NavEnableKeyboard
NavEnableGamepad
io.ConfigNavCaptureKeyboard
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x0000000E
HasMouseCursors
HasSetMousePos
RendererHasVtxOffset
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000000, TexSize: 512,64
io.DisplaySize: 1280.00,720.00
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 8.00,8.00
style.WindowBorderSize: 1.00
style.FramePadding: 4.00,3.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 8.00,4.00
style.ItemInnerSpacing: 4.00,4.00
Details:
I am working on a small game engine using SDL2/OpenGL that also does hot reloading (function for rendering is loaded from a shared library).
I want to initialize ImGui in my main function and render the windows in the render function from a shared lib.
I've used Get/SetCurrentContext to have the same ImGuiContext in both the main program and the library
Init in main:
IMGUI_CHECKVERSION();
imguiContext_p = ImGui::CreateContext();
ImGuiIO& io = ImGui::GetIO();
(void)io;
io.ConfigFlags |=
ImGuiConfigFlags_NavEnableKeyboard; // Enable Keyboard Controls
io.ConfigFlags |=
ImGuiConfigFlags_NavEnableGamepad; // Enable Gamepad Controls
// Setup Dear ImGui style
ImGui::StyleColorsDark();
// ImGui::StyleColorsLight();
// Setup Platform/Renderer backends
ImGui_ImplSDL2_InitForOpenGL(window_p, glContext);
ImGui_ImplOpenGL3_Init(g_glslVersion);
ImGui::GetAllocatorFunctions(&imGuiAllocFunc,
&imGuiFreeFunc,
&imGuiUserData_p);Usage in shared lib:
if (imGuiInit)
{
ImGui::SetCurrentContext(imguiContext_p);
ImGui::SetAllocatorFunctions(imGuiAllocFunc,
imGuiFreeFunc,
imGuiUserData_p);
//ImGui_ImplOpenGL3_dllInit();
imGuiInit = true;
}
ImGui_ImplOpenGL3_NewFrame();
ImGui_ImplSDL2_NewFrame();
ImGui::NewFrame();
if (showDemoWindow)
ImGui::ShowDemoWindow(&showDemoWindow);
ImGui::Render();This crashes when trying to call the first OpenGL function on the shared lib side (glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);)
Backtrace:
Thread 1 "example_sdl2_op" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0 0x0000000000000000 in ?? ()
#1 0x00007fffe019d85e in ImGui_ImplOpenGL3_CreateDeviceObjects () at ../../backends/imgui_impl_opengl3.cpp:765
#2 0x00007fffe019c297 in ImGui_ImplOpenGL3_NewFrame () at ../../backends/imgui_impl_opengl3.cpp:415
#3 0x00007fffe00a6db5 in render (context_p=0x555555a791c0, window_p=0x555555896080) at shared.cpp:24
#4 0x0000555555559af9 in main () at main.cpp:169
When looking at it in GDB it seems like OpenGL functions pointers are not NULL in imgl3wProcs on shared lib side but calling it still results in a crash.
I've added ImGui_ImplOpenGL3_dllInit() function that only calls imgl3wInit() and calling it once on the shared lib side solves the crashing problem but I feel like there is something wrong in my setup/usage of ImGui
I've included a link to a PR that includes changed example_sdl2_opengl3 as well as ImGui_ImplOpenGL3_dllInit() that shows this issue
Is there a way to solve this issue without having to initialize OpenGl twice?
Thanks in advance.
Screenshots/Video:
No response
Minimal, Complete and Verifiable Example code:
Uncomment line 20 in shared.cpp to make it not crash