Removed export of methods from exported class (breaks windows DLL builds)

[iboB]

When building ImGui as a DLL on Windows there's a compilation error as Windows compilers don't allow giving a DLL interface to specific methods of a class which itself has a DLL interface. It should be one or the other.

[iboB]

perhaps CI jobs which build a shared library for different platforms should be added?

[ocornut]

Hello,

Thanks for the PR. There's already a CI job for this:

https://github.com/ocornut/imgui/runs/1417199898?check_suite_focus=true

See under Windows > Build example_null (as DLL)
Before merging this I would like this test to be reworked to reflect the issue you are seeing. Can you clarify your compiler, compile option, and try to create a separate PR (without this fix) that would rightly trigger an error/warning? Then once we have it we can merge both PR.

Thank you!

[ocornut]

That specific test is doing:

  echo '#ifdef _EXPORT'                                  >  example_single_file.cpp
  echo '#  define IMGUI_API __declspec(dllexport)'       >> example_single_file.cpp
  echo '#else'                                           >> example_single_file.cpp
  echo '#  define IMGUI_API __declspec(dllimport)'       >> example_single_file.cpp
  echo '#endif'                                          >> example_single_file.cpp
  echo '#define IMGUI_IMPLEMENTATION'                    >> example_single_file.cpp
  echo '#include "misc/single_file/imgui_single_file.h"' >> example_single_file.cpp
  cl.exe /D_USRDLL /D_WINDLL /D_EXPORT /I. example_single_file.cpp /LD /FeImGui.dll /link
  cl.exe /I. ImGui.lib /Feexample_null.exe examples/example_null/main.cpp

[rokups]

I am surprised this would produce an error, as neither our CI nor my own projects building in this configuration have any issues.

With that said, i would say change is still a good one, as it removes redundant API linkage specifiers. One on the struct does the job for all applicable methods.

[iboB]

https://github.com/iboB/imgui-dll/runs/1420026650?check_suite_focus=true#step:4:13

Visual Studio 2019 (but I'm 99% sure I'll get the same errors on other versions)

Just a dll with imgui.cpp

[iboB]

To make a PR without this fix which triggers the error would take me a bit more time, as I'd have to study the current CI configs, but sure. I'll have time for it tomorrow and I'll do it in 18-20 hours if no one else has done it by then

[iboB]

by they way on cmd echo doesn't work like echo on bash
echo 'foo' produces the literal 'foo' with quotes. So at a glance, the code you provided should produce the file:

'#ifdef _EXPORT'                                  
'#  define IMGUI_API __declspec(dllexport)'       
'#else'                                           
'#  define IMGUI_API __declspec(dllimport)'       
'#endif'                                          
'#define IMGUI_IMPLEMENTATION'                    
'#include "misc/single_file/imgui_single_file.h"' 

Unless GH actions provides some other magic. But the strange thing is that this is not valid C++. It should fail with different compilation errors. So for now I hace no idea what's going on with the CI

[iboB]

Ok. This got me intrigued and instead of sleeping I made some experiments.

So it turns out that for some reason none of the code after

https://github.com/ocornut/imgui/blob/master/.github/workflows/build.yml#L74

... gets executed. Calling vcvarsall simply terminates the step

Thus, the bad echo's don't even get executed. If they were executed, they would produce an error like "too many characters in char literal" (see prev comment)

I have continued experimenting in my repo from above, and no matter what I add after the vcvarsall call, it always completes sucessfully.

I'll come up with a solution tomorrow (or... you know... today if I can't sleep because of this)

[iboB]

spoiler: it was today 😞

[ocornut]

Merged jointly in fcc2b71, thank you!