Joshua,

on Mon, 6 Jul 2026 11:15:28 -0400 you (Joshua Berne <berne_at_[hidden]>) wrote:

> Is there any precedent for a control macro (one defined by users to
> alter the behavior of the program, not by the implementation itself)
> to begin with __? Or to begin with STDC? Or any other particular
> form? I could not find any other obvious examples in C or C++ other
> than NDEBUG whose naming convention we hopefully don't want to use as
> a precedent.

We currently have `__STDC_WANT_IEC_60559_EXT__`,
`__STDC_WANT_IEC_60559_TYPES_EXT__` and `__STDC_WANT_LIB_EXT1__` that
have such a form and semantics.

> Having users define a reserved name to control the behavior seems
> backwards, as it mixes the responsibility of who is defining reserved
> names.

yes, probably, but we have some of these names in both standards, in
particular `main` ;-)

Thanks
Jₑₙₛ

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