Fix implicitly-deleted default constructor error on older Xcode versions#8719
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@tlively I'm afraid to say Gemini came up with move 90% of this, but it seems reasonable. I don't have any easy way to test on the older Xcode though. |
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Older versions of Clang (particularly those shipped with older Xcode versions) are more strict about the initialization of const members. According to the C++ standard, if a class has a const member that is not initialized at the point of declaration and lacks a user-provided default constructor that initializes it, the default constructor is implicitly deleted. While newer versions of Clang and other compilers may allow this if the member has a trivial default constructor (like our View struct, which has an inline initializer for its only member), older versions of Apple Clang have been known to reject this, leading to build failures when inheriting from IString (e.g., in the Name class). This change provides an explicit default constructor for IString that initializes the 'str' member, ensuring compatibility across a wider range of compiler versions.
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In emsdk we actually build on macos-13, but sadly there is not macos-13
available in github actions.
In doing this I'm trying to get binaryen CI to reproduce the current
issue we are seeing in emsdk CI:
```
In file included from /Users/distiller/project/binaryen/main/src/ir/import-names.h:23:
/Users/distiller/project/binaryen/main/src/support/name.h:35:12: error: call to implicitly-deleted default constructor of 'wasm::IString'
Name() : IString() {}
^
/Users/distiller/project/binaryen/main/src/support/istring.h:72:3: note: explicitly defaulted function was implicitly deleted here
IString() = default;
^
/Users/distiller/project/binaryen/main/src/support/istring.h:68:14: note: default constructor of 'IString' is implicitly deleted because field 'str' of const-qualified type 'const wasm::IString::View' would not be initialized
const View str;
^
```
Split out from #8719
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Older versions of Clang (particularly those shipped with older Xcode versions) are more strict about the initialization of const members. According to the C++ standard, if a class has a const member that is not initialized at the point of declaration and lacks a user-provided default constructor that initializes it, the default constructor is implicitly deleted.
While newer versions of Clang and other compilers may allow this if the member has a trivial default constructor (like our View struct, which has an inline initializer for its only member), older versions of Apple Clang have been known to reject this, leading to build failures when inheriting from IString (e.g., in the Name class).
This change provides an explicit default constructor for IString that initializes the 'str' member, ensuring compatibility across a wider range of compiler versions.