Use C99 named initialisers in core structs that define MGVTBLs #22086
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I thought we couldn't use this in public headers because C++? |
Ugh; it's |
It gets included in |
Another option would be to generate a separate The |
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@leonerd, Given where we are in our annual production cycle, are you thinking of this for 5.40 or 5.42? |
leonerd
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Oh it doesn't need to be in 5.40 at all; it isn't doing any kind of user-benefit change. It's purely tidying up the code internally for our benefit. It can wait for 5.42, I just happen to have started writing it now. |
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Looking more closely at things, |
Since most Magic vtables do not provide every function, using C99 named initialisers allows us to more easily specify which ones are present, so readers don't have to count commas. Additionally provides a layer of robustness in case more functions are added in future.
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These named initialisers are not permitted by C++ compilers using standards older than C++20, but fortunately even though they appear in mg_vtable.h and hence perl.h, they are hidden behind an `#ifdef` that is only defined when compiling `globals.c`, so this should be fine.
leonerd
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C99 allows trailing commas in on struct and table initialisers, so get rid of the code to avoid it in PL_magic_vtables and adjust the _names code to match. We don't add it to the enum, since magic_vtable_max is always the last element, so there won't be any diff noise from adding new elements after it.
| [want_vtbl_arylen] = "arylen", | ||
| [want_vtbl_arylen_p] = "arylen_p", | ||
| [want_vtbl_backref] = "backref", | ||
| [want_vtbl_checkcall] = "checkcall", | ||
| [want_vtbl_collxfrm] = "collxfrm", | ||
| [want_vtbl_dbline] = "dbline", | ||
| [want_vtbl_debugvar] = "debugvar", | ||
| [want_vtbl_defelem] = "defelem", | ||
| [want_vtbl_destruct] = "destruct", | ||
| [want_vtbl_env] = "env", | ||
| [want_vtbl_envelem] = "envelem", |
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Array designated initializers are not C++ compatible, and since we have people who build perl with a C++ compiler, it's excluded by the guide in perlhacktips.pod.
g++ supports it as an extension. but MSVC doesn't.
jkeenan
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Since most Magic vtables do not provide every function, using C99 named initialisers allows us to more easily specify which ones are present, so readers don't have to count commas. Additionally provides a layer of robustness in case more functions are added in future.
(No rush before 5.39.9 but I would like to test this out at least, sometime before too long)