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[lex.name] prohibits uses of predefined macro names and feature-test macros CWG 2818 #5296
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I think the permission added to [version.syn] will also need something like [cpp.predefined]'s p4, that is, that a library feature-test macro is not subject of
#defineand#undef. But that is not relevant to the issue at hand.IIUC this issue touches the same area as #5187.
In addition to the standard, implementations generally provide their own feature test macros. I think we should (conditionally) allow usage of these macros.IIUC this issue touches the same area as #5187.
Indeed.
In addition to the standard, implementations generally provide their own feature test macros. I think we should (conditionally) allow usage of these macros.
I had considered this. But my conclusion was that implementations can define that so as not to fall under the standard's NDR. They probably already do that with
__is_sameand family.- changed the title
[-][lex.name] prohibits uses of predefined macro names and feature-test macros[/-][+][lex.name] prohibits uses of predefined macro names and feature-test macros CWG2818[/+]on Nov 12, 2023 - changed the title
[-][lex.name] prohibits uses of predefined macro names and feature-test macros CWG2818[/-][+][lex.name] prohibits uses of predefined macro names and feature-test macros CWG 2818[/+]on Nov 12, 2023
This seems to prohibit uses of predefined macro names and library feature-test macros.
More formally, according to [intro.compliance.general],
Permission to use predefined macro names and library feature-test macros needs to be added to [cpp.predefined] and [version.syn], respectively. For full effect, amend [lex.name]p3's "otherwise" to "unless otherwise specified".