compile fails with mingw due to cludgy defines

[DJQuardaboff]

Many importers and converters include files which include windows.h. In mingw, windows.h (and other files) contain a line like:
#define interface struct
...
oof

/* Some kludge for Obj-C.
   For Obj-C the 'interface' is a keyword, but interface is used
   in midl-code too.  To resolve this conflict for at least the
   main windows API header, we define it here temporary.  */

It obviously does not work well with Corrade::PluginManager::Implementation::StaticPlugin in AbstractManager.h, which contains a const char* interface, and when referenced produces this error for me:

In file included from C:/msys64/mingw64/x86_64-w64-mingw32/include/oleidl.h:7,
                 from C:/msys64/mingw64/x86_64-w64-mingw32/include/ole2.h:38,
                 from C:/msys64/mingw64/x86_64-w64-mingw32/include/wtypes.h:12,
                 from C:/msys64/mingw64/x86_64-w64-mingw32/include/winscard.h:10,
                 from C:/msys64/mingw64/x86_64-w64-mingw32/include/windows.h:97,
                 from C:/git/magnum-plugins/src/external/dr/dr_flac.h:3630,
                 from C:/git/magnum-plugins/src/MagnumPlugins/DrFlacAudioImporter/DrFlacImporter.cpp:37:
C:/git/magnum-plugins/src/MagnumPlugins/DrFlacAudioImporter/DrFlacImporter.cpp: In function 'int pluginImporter_DrFlacAudioImporter()':
C:/git/magnum-plugins/src/MagnumPlugins/DrFlacAudioImporter/DrFlacImporter.cpp:195:1: error: expected unqualified-id before 'struct'
  195 | CORRADE_PLUGIN_REGISTER(DrFlacAudioImporter, Magnum::Audio::DrFlacImporter,
      | ^~~~~~~~~~~~~~~~~~~~~~~

I temporarily solved it by slapping an #undef interface right before the CORRADE_PLUGIN_REGISTER.

[DJQuardaboff]

libs affected for me were:
DrFlacAudioImporter
JpegImageConverter
JpegImporter
TinyGltfImporter

[mosra]

Uh oh. I'm aware of this silly define, and here I'm attempting to #undef it: https://github.com/mosra/corrade/blob/9584912024ea813073ffc15b3c13e3a68a33975d/src/Corrade/PluginManager/AbstractManager.h#L45-L49

The MinGW build on the CI compiles the plugins fine and I'm not aware of any similar reports, so this has to be either new in recent MinGW or you have something special in your build that defines it again after it's undef'd. What's the MinGW version you have?

@williamjcm are you running into this issue as well?

[DJQuardaboff]

Thank you for your fast replies

I'm not sure if this is good enough for the mingw version

MINGWBASEDIR=C:\msys64\mingw64
gcc version 9.1.0 (Rev3, Built by MSYS2 project)
gcc version 9.1.0 (Rev3, Built by MSYS2 project)
GNU gdb (GDB) 8.3
GNU ld (GNU Binutils) 2.30
GNU windres (GNU Binutils) 2.30
GNU dlltool (GNU Binutils) 2.30
GNU Make 4.2.1

It looks like windows.h gets included after the interface undef.
DrFlacImporter.cpp:

#include "DrFlacImporter.h" // << this is where interface is undef'd

#include <Corrade/Containers/ScopeGuard.h>
#include <Corrade/Utility/Assert.h>
#include <Corrade/Utility/Debug.h>
#include <Corrade/Utility/Endianness.h>

#include <Magnum/Math/Packing.h>

#define DR_FLAC_IMPLEMENTATION
#include "dr_flac.h" // << this seems to include windows.h

[williamjcm]

@williamjcm are you running into this issue as well?

Nope. Though at the same time, I don't use any of the mentioned plugins.

EDIT: Also, IIRC, the magnum-plugins package in the MSYS2 repos has those plugins enabled, but it builds without issues.

[mosra]

Argh, I have no idea why there would be a difference 😅 If I can't reproduce this, I can't reliably fix all occurences. I can probably manage to fix this for DrFlac by defining DR_FLAC_NO_STDIO, but I have no idea why libjpeg would need windows.h.

@DJQuardaboff if you add -DWIN32_LEAN_AND_MEAN to your CMAKE_CXX_FLAGS, does this go away? Or, what's the exact compiler command line that is used?

[DJQuardaboff]

The magnum-plugins package in the MSYS2 repos is fine because it's v2019.01. The struct with member interface wasn't in corrade in 2019.01.

Command line:

cd /C/git/magnum-plugins/cmake-build-release-mingw64/src/MagnumPlugins/DrFlacAudioImporter && /C/msys64/mingw64/bin/g++.exe  -DCORRADE_STATIC_PLUGIN -DUNICODE -D_UNICODE -I/C/git/magnum-plugins/src -I/C/git/magnum-plugins/cmake-build-release-mingw64/src -isystem /C/git/magnum-plugins/src/external/dr -isystem /C/msys64/mingw64/include/AL  -O3 -DNDEBUG   -std=c++11 -Wall -Wextra -Wold-style-cast -Winit-self -Werror=return-type -Wmissing-declarations -pedantic -fvisibility=hidden -fvisibility-inlines-hidden -Wzero-as-null-pointer-constant -Wdouble-promotion -o CMakeFiles/DrFlacAudioImporter.dir/DrFlacImporter.cpp.obj -c /C/git/magnum-plugins/src/MagnumPlugins/DrFlacAudioImporter/DrFlacImporter.cpp

Adding -DWIN32_LEAN_AND_MEAN fixed both DrFlacAudioImporter and TinyGltfImporter, but JpegImageConverter and JpegImporter fail because they include shlwapi.h
JpegImporter error:

In file included from C:/msys64/mingw64/x86_64-w64-mingw32/include/wtypes.h:7,
                 from C:/msys64/mingw64/x86_64-w64-mingw32/include/shtypes.h:23,
                 from C:/msys64/mingw64/x86_64-w64-mingw32/include/shlwapi.h:17,
                 from C:/msys64/mingw64/include/jmorecfg.h:19,
                 from C:/msys64/mingw64/include/jpeglib.h:31,
                 from C:/git/magnum-plugins/src/MagnumPlugins/JpegImporter/JpegImporter.cpp:40:
C:/git/magnum-plugins/src/MagnumPlugins/JpegImporter/JpegImporter.cpp: In function 'int pluginImporter_JpegImporter()':
C:/git/magnum-plugins/src/MagnumPlugins/JpegImporter/JpegImporter.cpp:153:1: error: expected unqualified-id before 'struct'
  153 | CORRADE_PLUGIN_REGISTER(JpegImporter, Magnum::Trade::JpegImporter,
      | ^~~~~~~~~~~~~~~~~~~~~~~

(rpc.h is where the actual #define interface struct is)
In jmorecfg.h:

#include <shlwapi.h> /* typedefs INT16 and INT32 */

It compiles even when commented out, so the flag NOSHLWAPI seems useful (and does solve the problem for me)
Actually, NOSHLWAPI, seems to fix everything, huh (kinda ominous tbh. I looked through pre-processor #if statements for a reason this works and I didn't find one)
btw, rpc.h is where all 4 errors point to. #define interface struct seems to be everywhere
btw again, this is at the bottom of windows.h (and ONLY windows.h):

/* Restore old value of interface for Obj-C.  See above.  */
#ifdef __OBJC__
#pragma pop_macro("interface")
#endif

DR_FLAC_NO_WIN32_IO also works for DrFlacAudioImporter.

[williamjcm]

The magnum-plugins package in the MSYS2 repos is fine because it's v2019.01

Nope, it's 2019.10. However, I noticed the magnum-integration package is still 2019.01, so I'll mention that to the repos' maintainers.

[DJQuardaboff]

Yes, my bad I didn't refresh the pacman database.
Since this seems like a non-issue now, should i close it?

[mosra]

@DJQuardaboff ah, so if I understand correctly, the issue disappears when updating to latest? :)

I'll add DR_FLAC_NO_WIN32_IO because it seems like a good thing to do regardless.

[DJQuardaboff]

The problem is still there if compiling v2019.10 on mingw, but the mingw pacman has precompiled binary for it. My specific problem is solved.

[mosra]

Can you upload your CMakeCache.txt from the build directory where the compilation fails? Or the whole thing, including cloned sources? I'll try to investigate.

[DJQuardaboff]

https://drive.google.com/drive/folders/1gXT692jvbpmFkk-9Zcm6F51xCCmW8F9U?usp=sharing
Running git status on corrade and magnum-plugins return the same thing:

HEAD detached at v2019.10
Untracked files:
  (use "git add <file>..." to include in what will be committed)

        cmake-build-release-mingw64/

ps. I tried install a fresh copy of mingw to make sure I wasn't crazy and it didn't play nice with cmake... :(

[mosra]

Yay, thank you! This helped me to finally reproduce -- https://ci.appveyor.com/project/mosra/magnum-plugins/build/next-1030/job/72472c9idmuweyaw ... somehow this happens only when the plugins are built static (and I forgot to ask about that before 😅).

Investigating why, will push a fix once I know what's to blame.