redundant #include of module 'std.depr.string_h' appears within namespace 'ImStb'

[mnesarco]

Dear ImGui 1.86 WIP (18502)

sizeof(size_t): 8, sizeof(ImDrawIdx): 2, sizeof(ImDrawVert): 20
define: __cplusplus=202002
define: IMGUI_DISABLE_OBSOLETE_FUNCTIONS
define: linux
define: GNUC=4
define: clang_version=12.0.1
define: IMGUI_HAS_VIEWPORT
define: IMGUI_HAS_DOCK

io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_opengl3

Version/Branch of Dear ImGui:

Version: Dear ImGui 1.86 WIP (18502)
Branch: docking

Back-end/Renderer/Compiler/OS

io.BackendPlatformName: imgui_impl_glfw
io.BackendRendererName: imgui_impl_opengl3
Compiler: Clang 12
Operating System: Linux Mint 19.3

My Issue/Question:

I am having a strange compilation error from imstb_textedit.h:387

The error disappears if I comment that line:

imgui/imstb_textedit.h

Line 387 in fc198fe

#include <string.h>

Screenshots/Video

[build] FAILED: 3rdparty/imgui/CMakeFiles/imgui.dir/Debug/vendor/imgui_widgets.cpp.o 
[build] ccache /usr/bin/c++ -DCMAKE_INTDIR=\"Debug\" -I/home/dev/3rdparty/imgui/src -I/home/dev/3rdparty/imgui/vendor/backends -I/home/dev/3rdparty/imgui/vendor -march=native -Wno-unused-command-line-argument -fuse-ld=lld -stdlib=libc++ -fno-builtin -fmodules -fbuiltin-module-map -Wall -Wextra -Wpedantic -Wmove -Wdangling -g -std=gnu++20 -MD -MT 3rdparty/imgui/CMakeFiles/imgui.dir/Debug/vendor/imgui_widgets.cpp.o -MF 3rdparty/imgui/CMakeFiles/imgui.dir/Debug/vendor/imgui_widgets.cpp.o.d -o 3rdparty/imgui/CMakeFiles/imgui.dir/Debug/vendor/imgui_widgets.cpp.o -c /home/dev/3rdparty/imgui/vendor/imgui_widgets.cpp
[build] In file included from /home/dev/3rdparty/imgui/vendor/imgui_widgets.cpp:3768:
[build] /home/dev/3rdparty/imgui/vendor/imstb_textedit.h:387:1: error: redundant #include of module 'std.depr.string_h' appears within namespace 'ImStb' [-Wmodules-import-nested-redundant]
[build] #include <string.h>
[build] ^
[build] /home/dev/3rdparty/imgui/vendor/imgui_widgets.cpp:3666:1: note: namespace 'ImStb' begins here
[build] namespace ImStb
[build] ^
[build] 1 error generated.

Standalone, minimal, complete and verifiable example:

It is complicated to isolate it, it is part of a big project, but I updated ImGui recently and today I deleted the build and cache dirs and rebuild everything and i get this error.

I am not sure what is happening, maybe someone have seen this before.

[rokups]

Neither STB nor Dear ImGui libraries support modules currently, therefore you should not try to build Dear ImGui with -fmodule. You could build Dear ImGui as a static library not using modules and then export library interface like so:

// imgui.cppm
module;
#include "imgui.h"
export module imgui;

[mnesarco]

Thank you @rokups .

[JohelEGP]

The issue is that the #include happens within namespace ImStb:

imgui/imgui_internal.h

Lines 206 to 208 in f1781c2

	#include "imstb_textedit.h"
	} // namespace ImStb

imgui/imstb_textedit.h

Line 390 in f1781c2

#include <string.h>

I'm not compiling Dear ImGui as a module,
but using Clang Modules,
which performs include translation on #include <string.h>.
Can I provide a PR to close and reopen the namespace between the #include?

[ocornut]

Since it seems to only happen here I would define the memmove define the lib is using to avoid the include.

[JohelEGP]

I will leave that to a more brave soul.
I don't know if the uses of memmove in imstb_textedit.h are performance sensitive
and don't feel like attempting to write a version that competes with the one in <string.h>.
For now, I just unwrapped the namespace around the #include in #6653.

[ocornut]

I meant that just specifying “ #define STB_TEXTEDIT_memmove memmove” on our end would completely side-step the problem, since we already have included the header and have access to memmove.

[JohelEGP]

I understand.
I suspected it was already included, given the error message.
I will readjust the PR.

[ocornut]

Your readjustment seems to be doing something else (you removed include from stb_textedit.h)
I'll push a separate commit with the correct solution.