[Develop] Cannot compile source code using non-Apple `clang`, showing "could not build module QuartzCore and CoreVideo", on macOS

[OzelotVanilla]

Tested versions

Current master branch (4.5 dev).

System information

macOS 15.5 (24F74)

Issue description

This issue is discussing the fail of compiling source code problem found in engine development. It does not related to the release of any version.
See PR #107200 for current fixing.

(Some part copied from #106820 (comment))

These two lines (L42 and L43; L42 is a comment) makes the compilation failing when not using clang at /usr/bin/clang.

godot/drivers/metal/SCsub

Line 43 in de37627

env_metal.Append(CCFLAGS=["-fmodules", "-fcxx-modules"])

More specificly speaking, the -fmodules flag causes problem.

These lines are introduced in this commit by this PR #105628:
4572994#diff-1b97ad843ac03b1910b3b5b6888d75e1d0a5ea9a51919f28cd0b1ccb1b49fc8a

In this comment #105628 (comment), they explain the reason why the line mentioned above, is added. But as they had said, this is not widely supported by all compilers, so my compiler (clang v20.1.5, from homebrew) failed to build.

I have a pull-request #107200 which may fix this problem by checking if the clang is Apple-clang or not, but I still hope the root cause could be found.

This is a part of the log when the compiler fails. The whole log is too long, but expected function body after function declarator error could be seen a lot of times in these logs.

While building module 'QuartzCore' imported from drivers/metal/metal_objects.h:63:
While building module 'CoreVideo' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/CAOpenGLLayer.h:9:
While building module 'ApplicationServices' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/CoreVideo.framework/Headers/CVImageBuffer.h:29:
While building module 'CUPS' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/ApplicationServices.framework/Frameworks/PrintCore.framework/Headers/PDEPluginInterface.h:24:
In file included from <module-includes>:1:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/cups/cups.h:428:60: error: expected function body after function declarator
  428 | extern cups_file_t      *cupsTempFile2(char *filename, int len) _CUPS_API_1_2;
      |                                                                 ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/cups/versioning.h:112:27: note: expanded from macro '_CUPS_API_1_2'
  112 | #    define _CUPS_API_1_2 API_AVAILABLE(macos(10.5), ios(11.0)) _CUPS_PUBLIC
      |                           ^
While building module 'QuartzCore' imported from drivers/metal/metal_objects.h:63:
While building module 'CoreVideo' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/CAOpenGLLayer.h:9:
While building module 'ApplicationServices' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/CoreVideo.framework/Headers/CVImageBuffer.h:29:
While building module 'CUPS' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/ApplicationServices.framework/Frameworks/PrintCore.framework/Headers/PDEPluginInterface.h:24:
In file included from <module-includes>:1:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/cups/cups.h:433:20: error: expected function body after function declarator
  433 |                                          int outfile) _CUPS_API_1_3;
      |                                                       ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/cups/versioning.h:113:27: note: expanded from macro '_CUPS_API_1_3'
  113 | #    define _CUPS_API_1_3 API_AVAILABLE(macos(10.5), ios(11.0)) _CUPS_PUBLIC
      |                           ^
While building module 'QuartzCore' imported from drivers/metal/metal_objects.h:63:
While building module 'CoreVideo' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/CAOpenGLLayer.h:9:
While building module 'ApplicationServices' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/CoreVideo.framework/Headers/CVImageBuffer.h:29:
While building module 'CUPS' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/ApplicationServices.framework/Frameworks/PrintCore.framework/Headers/PDEPluginInterface.h:24:
In file included from <module-includes>:1:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/cups/cups.h:437:12: error: expected function body after function declarator
  437 |                                        _CUPS_API_1_3;
      |                                        ^
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/usr/include/cups/versioning.h:113:27: note: expanded from macro '_CUPS_API_1_3'
  113 | #    define _CUPS_API_1_3 API_AVAILABLE(macos(10.5), ios(11.0)) _CUPS_PUBLIC
      |                           ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
While building module 'QuartzCore' imported from drivers/metal/metal_objects.h:63:
While building module 'CoreVideo' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/CAOpenGLLayer.h:9:
While building module 'ApplicationServices' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/CoreVideo.framework/Headers/CVImageBuffer.h:29:
In file included from <module-includes>:1:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/ApplicationServices.framework/Headers/ApplicationServices.h:62:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/ApplicationServices.framework/Frameworks/PrintCore.framework/Headers/PrintCore.h:26:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/ApplicationServices.framework/Frameworks/PrintCore.framework/Headers/PDEPluginInterface.h:24:9: fatal error: could not build module 'CUPS'
   24 | #import <cups/ppd.h>
      |  ~~~~~~~^
While building module 'QuartzCore' imported from drivers/metal/metal_objects.h:63:
While building module 'CoreVideo' imported from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/CAOpenGLLayer.h:9:
In file included from <module-includes>:1:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/CoreVideo.framework/Headers/CoreVideo.h:29:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/CoreVideo.framework/Headers/CVPixelBuffer.h:23:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/CoreVideo.framework/Headers/CVImageBuffer.h:29:10: fatal error: could not build module 'ApplicationServices'
   29 | #include <ApplicationServices/ApplicationServices.h>
      |  ~~~~~~~~^
While building module 'QuartzCore' imported from drivers/metal/metal_objects.h:63:
In file included from <module-includes>:1:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/QuartzCore.h:20:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/CoreAnimation.h:34:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.4.sdk/System/Library/Frameworks/QuartzCore.framework/Headers/CAOpenGLLayer.h:9:9: fatal error: could not build module 'CoreVideo'
    9 | #import <CoreVideo/CVBase.h>
      |  ~~~~~~~^
In file included from drivers/metal/metal_objects.mm:51:
drivers/metal/metal_objects.h:63:9: fatal error: could not build module 'QuartzCore'
   63 | #import <QuartzCore/CAMetalLayer.h>
      |  ~~~~~~~^
24 errors generated.
scons: *** [bin/obj/drivers/metal/metal_objects.macos.editor.arm64.o] Error 1
scons: building terminated because of errors.
INFO: Time elapsed: 00:01:12.29

Steps to reproduce

• Use brew install llvm to install Homebrew-clang.
• Run PATH=/opt/homebrew/opt/llvm/bin:$PATH scons

Minimal reproduction project (MRP)

Use the code in master branch.

[OzelotVanilla]

By the way, when using homebrew-clang with -fmodules are not enabled, instead of the error above, these warning generates:

[ 49%] drivers/metal/pixel_formats.mm:579:41: warning: mixture of designated and non-designated initializers in the same initializer list is a C99 extension [-Wc99-designator]
  579 |         _mtl_pixel_format_descs[p_pix_fmt] = { .mtlPixelFormat = p_pix_fmt, DataFormat::DATA_FORMAT_MAX, p_fmt_caps, p_view_class, p_pix_fmt_linear, p_name };
      |                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/metal/pixel_formats.mm:579:70: note: first non-designated initializer is here
  579 |         _mtl_pixel_format_descs[p_pix_fmt] = { .mtlPixelFormat = p_pix_fmt, DataFormat::DATA_FORMAT_MAX, p_fmt_caps, p_view_class, p_pix_fmt_linear, p_name };
      |                                                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/metal/pixel_formats.mm:781:42: warning: mixture of designated and non-designated initializers in the same initializer list is a C99 extension [-Wc99-designator]
  781 |         _mtl_vertex_format_descs[mtlVtxFmt] = { .mtlVertexFormat = mtlVtxFmt, RD::DATA_FORMAT_MAX, vtxCap, MTLViewClass::None, MTLPixelFormatInvalid, name };
      |                                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/metal/pixel_formats.mm:781:72: note: first non-designated initializer is here
  781 |         _mtl_vertex_format_descs[mtlVtxFmt] = { .mtlVertexFormat = mtlVtxFmt, RD::DATA_FORMAT_MAX, vtxCap, MTLViewClass::None, MTLPixelFormatInvalid, name };
      |                                                                               ^~~~~~~~~~~~~~~~~~~
2 warnings generated.
drivers/metal/metal_objects.mm:1933:2: warning: array designators are a C99 extension [-Wc99-designator]
 1933 |         [RD::SHADER_STAGE_VERTEX] = "vert",
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~
[ 50%] Compiling editor/editor_translation.cpp ...
[ 50%] Compiling modules/text_server_adv/script_iterator.cpp ...
[ 50%] Compiling modules/text_server_adv/text_server_adv.cpp ...
[ 50%] Compiling modules/text_server_adv/register_types.cpp ...
[ 50%] Compiling modules/text_server_adv/thorvg_svg_in_ot.cpp ...
[ 50%] Compiling editor/editor_translation_parser.cpp ...
[ 50%] Compiling editor/editor_undo_redo_manager.cpp ...
[ 50%] Compiling editor/editor_vcs_interface.cpp ...
drivers/metal/rendering_device_driver_metal.mm:1817:3: warning: array designators are a C99 extension [-Wc99-designator]
 1817 |                 [ATTACHMENT_LOAD_OP_LOAD] = MTLLoadActionLoad,
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/metal/rendering_device_driver_metal.mm:1823:3: warning: array designators are a C99 extension [-Wc99-designator]
 1823 |                 [ATTACHMENT_STORE_OP_STORE] = MTLStoreActionStore,
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~
[ 50%] Compiling editor/engine_update_label.cpp ...

[stuartcarnie]

Godot uses LLVM (on Linux) to build official releases, and these flags are not causing an issue, I agree removing -fmodules is not the answer nor is -fmodules the root cause.

Can I ask what your use case is for building Apple binaries with LLVM, given you are compiling on macOS anyway?

Note

I should be clear that it is Apple's fork of LLVM that we use

Thanks for the clarification, @bruvzg

[OzelotVanilla]

Can I ask what your use case is for building Apple binaries with LLVM, given you are compiling on macOS anyway?

The reason is not related to godot itself (so it looks a bit off-topic here).

However for the documentation page, no requirements for compiler (type or version) is written in the requirement, so for me I believe somehow that, the latest version of compiler is considered acceptable when compiling. At least works for Vulkan I installed from brew, it looks fine.

Maybe it is also good to let scons to check the compiler's type and version the user are using ?

[bruvzg]

However for the documentation page, no requirements for compiler (type or version) is written in the requirement, so for me I believe somehow that, the latest version of compiler is considered acceptable when compiling.

It's listing Xcode as requirement, and compiler is part of it.

At least works for Vulkan I installed from brew, it looks fine.

Homebrew libraries usually have a hardcoded path, so it will work on your system, but resulting export templates might be non-portable.

[OzelotVanilla]

I got what you said. Can we say that the homebrew installed clang, or the hardcoded path, could be the root of this compilation error ?

[bruvzg]

Homebrew clang definitely is the core of issue, its unmodified upstream LLVM, and both Xcode and OSXCross use a modified Apple version.

Hardcoded paths are not related. It just something to consider when building something you intend to distribute, it might not work on other macs without Homebrew and specific Homebrew packages installed.