Enabling ASAN produces alignment warning when hovering over table headers

[justSomeFella]

Dear ImGui 1.82 WIP (18101)
--------------------------------
sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=201402
define: __linux__
define: __GNUC__=9
--------------------------------
io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_opengl3
io.ConfigFlags: 0x00000000
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

Version/Branch of Dear ImGui:

Version: 1.8.2
Branch: master

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_glfw.cpp + imgui_impl_opengl3.cpp
Compiler:
g++ (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
cc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0

Operating System: Ubuntu 20.04.2 LTS

My Issue/Question:

Hello!

I was compiling imgui with address sanitizer in a separate project and I noticed some warnings spitting out to the console when using the tables branch and hovering over a header. I was able to produce a MVE by adding the address sanitizer flags to the example 'example_glfw_opengl3' Makefile in the imgui repo.

Created a fork and branch here:
https://github.com/justSomeFella/imgui/tree/bug_report/alignment_warning

But will include relevant output in this issue as well.

Screenshots/Video
Log output included in the branch above, but included here as well

./example_glfw_opengl3 
../../imgui_internal.h:534:117: runtime error: reference binding to misaligned address 0x61800001335f for type 'struct ImGuiTableCellData', which requires 4 byte alignment
0x61800001335f: note: pointer points here
 03 04 05 06 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00
             ^ 
../../imgui_tables.cpp:1553:28: runtime error: member access within misaligned address 0x61800001335f for type 'struct ImGuiTableCellData', which requires 4 byte alignment
0x61800001335f: note: pointer points here
 03 04 05 06 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00
             ^ 
../../imgui_tables.cpp:1554:27: runtime error: member access within misaligned address 0x61800001335f for type 'struct ImGuiTableCellData', which requires 4 byte alignment
0x61800001335f: note: pointer points here
 03 04 05 06 42  96 fa cc 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00
             ^ 
../../imgui_tables.cpp:1725:77: runtime error: member access within misaligned address 0x61800001335f for type 'struct ImGuiTableCellData', which requires 4 byte alignment
0x61800001335f: note: pointer points here
 03 04 05 06 42  96 fa cc 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00
             ^ 
../../imgui_tables.cpp:1726:76: runtime error: member access within misaligned address 0x61800001335f for type 'struct ImGuiTableCellData', which requires 4 byte alignment
0x61800001335f: note: pointer points here
 03 04 05 06 42  96 fa cc 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00
             ^ 
../../imgui_tables.cpp:1730:48: runtime error: member access within misaligned address 0x61800001335f for type 'struct ImGuiTableCellData', which requires 4 byte alignment
0x61800001335f: note: pointer points here
 03 04 05 06 42  96 fa cc 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00

This happens when the steps

1. modified the Makefile to include -fsanitize=address,undefined
2. run the example_glfw_opengl3 binary
3. hover over any column heading in a table with the cursor
    for example (In the demo window) 
        Tables & columns -> Horizontal Scrolling -> Line #

I noticed it seems to happen once, as in I cannot get it spitting out the error again if I hover over the same table header.

Standalone, minimal, complete and verifiable example:
modify the CXX global flags section to include in examples/example_glfw_opengl3/Makefile

CXXFLAGS = -I$(IMGUI_DIR) -I$(IMGUI_DIR)/backends -fsanitize=address,undefined
CXXFLAGS += -g -Wall -Wformat
LDFLAGS = -fsanitize=address,undefined
LIBS =

Then run the example_glfw_opengl3 binary.

I did try crawling through the issues/todos below, but couldn't find anything specific to this output
#3740 (comment)

If there is any other output or information I can provide please feel free to let me know. The library has been great to use thus far, thank you for working on it!

[ocornut]

Thank you very much for this report.
This is now fixed by d8c88bd

And you gave us the idea to enable ASAN in our CI run for regression tests (covering a good portion of the codebase)!

[justSomeFella]

Thank you so much!

Cheers