Re: minimum required -std=c++NN?

On Tue, Jun 25, 2024 at 01:38:38PM +0200, Christoph Badura wrote:
> On Fri, Jun 21, 2024 at 03:05:42PM -0400, Greg Troxel wrote:
> >   C++20 is new, but that's how it is.  As for that file vs all of gcc,
> >   what does gcc's build instructions say?  If they don't, they are
> >   buggy.
> 
> I've not found anything in the build instructions that mentions that file
> (or directory) specifically neither a mention of c++20.
> 
> The build instructions say that gcc 12 needs a c++11 compiler.
> 
> Apparently both gcc10 and clang 14 know enough about c++20 in c++11 mode
> to compile the file but warn about the c++20 constructs.

I think it matters that these particular constructs are attributes, as,
quoting from https://en.cppreference.com/w/cpp/language/attributes :

  Besides the standard attributes listed below, implementations
  may support arbitrary non-standard attributes with implementation-defined
  behavior. All attributes unknown to an implementation are ignored
  without causing an error.(since C++17)

So the warning is just saying "I don't recognize that attribute, but I
happen to know that with my c++20 hat on, I would".

(Even if the attribute is recognized, the compiler is also allowed to
do nothing about it.)


Cheers,

Patrick