Re: [PATCH] Amend AC_CHECK_HEADER_STDBOOL for C++11 and modern dialects

[Paul Eggert]

On 06/01/2016 01:29 AM, David Seifert wrote:
> stdbool.m4 is supposed to merely check that
> stdbool.h fulfills C99 requirements. Why does it then necessarily 
> check whether bool is a
> defined _macro_?

Because C99 (and C11) require bool to be a macro.

m4/stdbool.m4 now does that check only inside #if __cplusplus < 201103, 
so I don't see why clang++ would complain now. Is it setting __cplusplus 
to an older value? Do older versions of the C++ standard require bool to 
be a macro?  (I don't use C++.)

> Wouldn't it be better to change the stdbool.m4 macro to instead try 
> and use "bool" in a statement
> or as a type

It depends on how strict the compatibility checking should be. Kind of a 
judgment call, I suppose. That being said, I don't see the harm in the 
current approach for C. Maybe it needs to be toned down for C++, but I'd 
like to know why before fiddling with this (it's been this way since at 
least 2002...).