Full name of submitter (unless configured in github; will be published with the issue): Hubert Tong
Reference (section label): cpp.cond
Link to reflector thread (if any): N/A
Issue description:
Consider (with the proposed offset parameter for a more plausible use case):
#if __has_embed(__FILE__ offset(\
defined(WANT_4K_SOURCE) ? 4095 : 0\
)) == __STDC_EMBED_EMPTY__
#error Desired source not found
#endif
It is unclear whether the above is ill-formed due to https://wg21.link/cpp.embed.param.limit#1 because https://wg21.link/cpp.cond#12 can be read as saying that the evaluation of the defined-macro-expression has occurred prior to the evaluation of the has-embed-expression.
Suggested resolution:
Add a restriction that
A defined-macro-expression shall not appear within a has-embed-expression.
"Editor's" note: This is for consistency with the restriction in the context of #embed, which is (in turn) motivated by the special macro expansion logic associated with defined only in the [cpp.cond] context. Since we are already in the [cpp.cond] context for __has_embed, there is no major design barrier for specifying that the defined-macro-expressions are evaluated first.
Full name of submitter (unless configured in github; will be published with the issue): Hubert Tong
Reference (section label): cpp.cond
Link to reflector thread (if any): N/A
Issue description:
Consider (with the proposed
offsetparameter for a more plausible use case):It is unclear whether the above is ill-formed due to https://wg21.link/cpp.embed.param.limit#1 because https://wg21.link/cpp.cond#12 can be read as saying that the evaluation of the defined-macro-expression has occurred prior to the evaluation of the has-embed-expression.
Suggested resolution:
Add a restriction that
"Editor's" note: This is for consistency with the restriction in the context of
#embed, which is (in turn) motivated by the special macro expansion logic associated withdefinedonly in the [cpp.cond] context. Since we are already in the [cpp.cond] context for__has_embed, there is no major design barrier for specifying that the defined-macro-expressions are evaluated first.