DragScalar clamp segment fault bug if only one of min/max value is provided

[harry75369]

Version/Branch of Dear ImGui:

Dear ImGui 1.80 (18000)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201703
define: __linux__
define: __GNUC__=10
--------------------------------
io.BackendPlatformName: imgui_impl_sdl
io.BackendRendererName: imgui_impl_opengl3
io.ConfigFlags: 0x00000020
 NoMouseCursorChange
io.ConfigInputTextCursorBlink
io.ConfigWindowsResizeFromEdges
io.ConfigMemoryCompactTimer = 60.0
io.BackendFlags: 0x0000000E
 HasMouseCursors
 HasSetMousePos
 RendererHasVtxOffset
--------------------------------
io.Fonts: 1 fonts, Flags: 0x00000000, TexSize: 512,1024
io.DisplaySize: 2000.00,1600.00
io.DisplayFramebufferScale: 1.00,1.00
--------------------------------
style.WindowPadding: 16.00,16.00
style.WindowBorderSize: 1.00
style.FramePadding: 8.00,6.00
style.FrameRounding: 0.00
style.FrameBorderSize: 0.00
style.ItemSpacing: 16.00,8.00
style.ItemInnerSpacing: 8.00,8.00

My Issue/Question:

If ImGui::DragScalar is provided only one of min/max values and ImGuiSliderFlags_AlwaysClamp is set, the program will segfault when input an out-of-bound value.

This is due to the bug in ImGui::TempInputScalar function where it attempts to invoke DataTypeCompare even if only one of min/max value is provided.

But for DataTypeCompare, both min/max values must be provided.

  3250 bool ImGui::TempInputScalar(const ImRect& bb, ImGuiID id, const char* label, ImGuiDataType data_type, void* p_data, const char* format, const void* p_clamp_min, const void* p_clamp_max)
  3251 {
  3252     ...
  3263     if (TempInputText(bb, id, label, data_buf, IM_ARRAYSIZE(data_buf), flags))
  3264     {
  3265         // Backup old value
  3266         size_t data_type_size = DataTypeGetInfo(data_type)->Size;
  3267         ImGuiDataTypeTempStorage data_backup;
  3268         memcpy(&data_backup, p_data, data_type_size);
  3269 
  3270         // Apply new value (or operations) then clamp
  3271         DataTypeApplyOpFromText(data_buf, g.InputTextState.InitialTextA.Data, data_type, p_data, NULL);
  3272         if (p_clamp_min || p_clamp_max) // NOTE HERE!
  3273         {
  3274             if (DataTypeCompare(data_type, p_clamp_min, p_clamp_max) > 0) // NOTE HERE!
  3275                 ImSwap(p_clamp_min, p_clamp_max);
  3276             DataTypeClamp(data_type, p_data, p_clamp_min, p_clamp_max);
  3277         }

Related commit: 36af398

My current fix is

  3272         if (p_clamp_min || p_clamp_max)
  3273         {
~ 3274             if (p_clamp_min && p_clamp_max && DataTypeCompare(data_type, p_clamp_min, p_clamp_max) > 0)
  3275                 ImSwap(p_clamp_min, p_clamp_max);
  3276             DataTypeClamp(data_type, p_data, p_clamp_min, p_clamp_max);
  3277         }

Hope it helps.

[ocornut]

Hello Chaoya,
Thanks for your report. I've looked at this and confirm that your suggested fix is correct.
The fix has been pushed to 0ecdf81.

Thank you!