Help with bindings for imgui library

[Xzya]

Hello,

I am trying to write bindings for imgui (cimgui) but I run in all kinds of problems, and I'm not sure what I'm doing wrong.

Here is my code, and I also have this test project with the minimal code to reproduce the problem.

Current I am getting the following errors:

# github.com/Xzya/go-imgui/imgui
cgo-gcc-prolog:47:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:60:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:61:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:62:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:63:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:94:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:111:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:156:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:157:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:158:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:159:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:175:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:176:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:177:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:178:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:179:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:180:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:181:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
cgo-gcc-prolog:182:17: error: field has incomplete type 'struct ImVec2'
imgui/cimgui/cimgui/cimgui.h:31:8: note: forward declaration of 'struct ImVec2'
fatal error: too many errors emitted, stopping now [-ferror-limit=]

and

# github.com/Xzya/go-bindings-test/imgui
imgui/cgo_helpers.go:121: ref74e98a33.x undefined (type *C.struct_ImVec2 has no field or method x)
imgui/cgo_helpers.go:125: ref74e98a33.y undefined (type *C.struct_ImVec2 has no field or method y)
imgui/cgo_helpers.go:149: x.ref74e98a33.x undefined (type *C.struct_ImVec2 has no field or method x)
imgui/cgo_helpers.go:150: x.ref74e98a33.y undefined (type *C.struct_ImVec2 has no field or method y)

I am not very familiar with C/C++, so there may be something very obvious that I am doing wrong.

Could you provide some help please?

Thank you!

[oakad]

At least one of your files should have CIMGUI_DEFINE_ENUMS_AND_STRUCTS define set.

[Xzya]

Hello,

I already tried this. Using #define CIMGUI_DEFINE_ENUMS_AND_STRUCTS 1 results in the following error:

# github.com/Xzya/go-imgui/imgui
In file included from imgui/cgo_helpers.go:9:
In file included from ./cgo_helpers.h:4:
./cimgui/cimgui/cimgui.h:84:8: error: redefinition of 'ImVec2'
struct ImVec2
       ^
./cimgui/cimgui/cimgui.h:84:8: note: previous definition is here
struct ImVec2
       ^
In file included from imgui/cgo_helpers.go:9:
In file included from ./cgo_helpers.h:4:
./cimgui/cimgui/cimgui.h:89:8: error: redefinition of 'ImVec4'
struct ImVec4
       ^
./cimgui/cimgui/cimgui.h:89:8: note: previous definition is here
struct ImVec4
       ^
In file included from imgui/cgo_helpers.go:9:
In file included from ./cgo_helpers.h:4:
./cimgui/cimgui/cimgui.h:96:5: error: redefinition of enumerator 'ImGuiWindowFlags_NoTitleBar'
    ImGuiWindowFlags_NoTitleBar = 1 << 0,
    ^
./cimgui/cimgui/cimgui.h:96:5: note: previous definition is here
    ImGuiWindowFlags_NoTitleBar = 1 << 0,
    ^
In file included from imgui/cgo_helpers.go:9:
In file included from ./cgo_helpers.h:4:
./cimgui/cimgui/cimgui.h:97:5: error: redefinition of enumerator 'ImGuiWindowFlags_NoResize'
    ImGuiWindowFlags_NoResize = 1 << 1,
    ^
...
many errors following the same pattern
...

I thought this was caused because the header was imported multiple times, so I tried adding #pragma once in the cimgui.h header, and the error changes to:

# github.com/Xzya/go-imgui/imgui
cgo-gcc-prolog:7306:41: warning: incompatible pointer types passing 'struct __va_list_tag *' to parameter of type 'struct __va_list_tag *' [-Wincompatible-pointer-types]
imgui/cimgui/cimgui/cimgui.h:781:102: note: passing argument to parameter 'args' here
cgo-gcc-prolog:7328:44: warning: incompatible pointer types passing 'struct __va_list_tag *' to parameter of type 'struct __va_list_tag *' [-Wincompatible-pointer-types]
imgui/cimgui/cimgui/cimgui.h:782:105: note: passing argument to parameter 'args' here
# github.com/Xzya/go-imgui/imgui
Undefined symbols for architecture x86_64:
  "_ImDrawData_DeIndexAllBuffers", referenced from:
      __cgo_3ccdb0436fb9_Cfunc_ImDrawData_DeIndexAllBuffers in imgui.cgo2.o
     (maybe you meant: __cgo_3ccdb0436fb9_Cfunc_ImDrawData_DeIndexAllBuffers)
  "_ImDrawData_ScaleClipRects", referenced from:
      __cgo_3ccdb0436fb9_Cfunc_ImDrawData_ScaleClipRects in imgui.cgo2.o
     (maybe you meant: __cgo_3ccdb0436fb9_Cfunc_ImDrawData_ScaleClipRects)
  "_ImDrawList_AddBezierCurve", referenced from:
      __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddBezierCurve in imgui.cgo2.o
     (maybe you meant: __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddBezierCurve)
  "_ImDrawList_AddCallback", referenced from:
      __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddCallback in imgui.cgo2.o
     (maybe you meant: __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddCallback)
  "_ImDrawList_AddCircle", referenced from:
      __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddCircle in imgui.cgo2.o
     (maybe you meant: __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddCircleFilled, __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddCircle )
  "_ImDrawList_AddCircleFilled", referenced from:
      __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddCircleFilled in imgui.cgo2.o
     (maybe you meant: __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddCircleFilled)
  "_ImDrawList_AddConvexPolyFilled", referenced from:
      __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddConvexPolyFilled in imgui.cgo2.o
     (maybe you meant: __cgo_3ccdb0436fb9_Cfunc_ImDrawList_AddConvexPolyFilled)

...
many errors following the same pattern
...

ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Compilation finished with exit code 2

My guess is that CIMGUI_DEFINE_ENUMS_AND_STRUCTS is only intended to be used when generating code. E.g. I am using it when generating the code with c-for-go because it doesn't see the type declarations from the C++ code (imgui.h).

Any ideas?
Thank you!

[xlab]

Undefined symbols for architecture x86_64:

Linking flags are missing, e.g. #cgo LDFLAGS or .c sources that contain those symbols.

[yaswagner]

Hi, I was wondering if there was a demo to understand how to use the binding generator? Thanks!

[sonoro1234]

https://github.com/cimgui/cimgui#generate-binding

[xlab]

@yaswagner instead of writing a generator that consumes cimgui's JSON (as @sonoro1234 suggests, right?), I'd use c-for-go with a generated cimgui.h.

There is a plenty examples in the repo, see Nuklear and Vulkan bindings, both are made for a single-file API header.

@yaswagner regarding to errors above, I fixed c-for-go a couple of days ago, it should avoid duplicates. Please try again.