OG_COUNTED_BY issue on Linux with Swift 6.1 compiler

[Kyle-Ye]

It can be compiled with Swift 6.0 but not with Swift 6.1.

The error message is

In file included from <redacted>/OpenGraph/Sources/OpenGraph_SPI/Attribute/AttributeID.cpp:8:
In file included from <redacted>/OpenGraph/Sources/OpenGraph_SPI/Attribute/AttributeID.hpp:12:
In file included from <redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGAttribute.h:12:
<redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGGraph.h:108:70: error: use of undeclared identifier 'count'; did you mean 'round'?
  108 | bool OGGraphAnyInputsChanged(const OGAttribute *inputs OG_COUNTED_BY(count), size_t count);
      |                                                                      ^~~~~
      |                                                                      round
<redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGBase.h:54:39: note: expanded from macro 'OG_COUNTED_BY'
   54 | #define OG_COUNTED_BY(N) __counted_by(N)
      |                                       ^
<redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGBase.h:48:55: note: expanded from macro '__counted_by'
   48 | #define __counted_by(N) __attribute__((__counted_by__(N)))
      |                                                       ^
/usr/lib/gcc/aarch64-linux-gnu/11/../../../../include/c++/11/math.h:107:12: note: 'round' declared here
  107 | using std::round;
      |            ^
In file included from <redacted>/OpenGraph/Sources/OpenGraph_SPI/Attribute/AttributeID.cpp:8:
In file included from <redacted>/OpenGraph/Sources/OpenGraph_SPI/Attribute/AttributeID.hpp:12:
In file included from <redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGAttribute.h:12:
<redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGGraph.h:108:56: warning: '__counted_by__' attribute ignored [-Wignored-attributes]
  108 | bool OGGraphAnyInputsChanged(const OGAttribute *inputs OG_COUNTED_BY(count), size_t count);
      |                                                        ^
<redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGBase.h:54:26: note: expanded from macro 'OG_COUNTED_BY'
   54 | #define OG_COUNTED_BY(N) __counted_by(N)
      |                          ^
<redacted>/OpenGraph/Sources/OpenGraph_SPI/include/OGBase.h:48:40: note: expanded from macro '__counted_by'
   48 | #define __counted_by(N) __attribute__((__counted_by__(N)))
      |                                        ^
1 warning and 1 error generated.
error: fatalError

[Kyle-Ye]

On Linux:

• The counted_by attribute is not supported on Swift 6.0 toolchain's clang.
• And counted_by is supported with Swift 6.1 toolchain's clang but required the count to be declared before use.

workaround:

#if OG_TARGET_OS_DARWIN
OG_EXPORT
//OG_REFINED_FOR_SWIFT
bool OGGraphAnyInputsChanged(const OGAttribute *inputs /*OG_COUNTED_BY(count)*/, size_t count);
#else
// __counted_by__ is supported with Swift 6.1+ toolchain's clang on Linux.
// But it required the count to be declared first which is not required on Apple clang.
// See https://github.com/OpenSwiftUIProject/OpenGraph/issues/130
OG_EXPORT
OG_REFINED_FOR_SWIFT
bool OGGraphAnyInputsChanged(size_t count, const OGAttribute *inputs OG_COUNTED_BY(count));
#endif

Also on Darwin platform:

1. There will be some warning when a cpp file include this __counted_by__ attached API. (It is not supported on C++ but will also evaluate to true)

See llvm/llvm-project#98836

2. There will have conflict with our definition with the SDK's ptrcheck.h defination.

Considering all the information, I think it would be better we do not use this attribute for now. And I'll revert the relevant change to "fix" the issue.

[Kyle-Ye]

Forum Post discussion on this: https://forums.swift.org/t/counted-by-regression-issue-on-swift-6-1-for-linux/80598/3