On Thu, 2025-03-13 at 14:53 +0000, Jonathan Wakely wrote:
> On Tue, 11 Feb 2025 at 22:44, Sérgio Basto <ser...@serjux.com> wrote:
> > 
> > On Tue, 2025-02-11 at 21:45 +0000, Jonathan Wakely wrote:
> > > On Tue, 28 Jan 2025 at 09:07, Jakub Jelinek <ja...@redhat.com>
> > > wrote:
> > > > 
> > > > On Mon, Jan 27, 2025 at 07:31:35PM +0000, Sérgio Basto via
> > > > devel
> > > > wrote:
> > > > > I just want check, if I'm thinking correctly before
> > > > > submitting a
> > > > > fix in
> > > > > gtest package
> > > > > 
> > > > > The problem is on Rawhide I have this warning that make other
> > > > > packages
> > > > > fail to build [1]
> > > > > 
> > > > > gtest source [2] source get __cplusplus value and include
> > > > > <version> or
> > > > > #include <ciso646>  depending on __cplusplus value .
> > > > > 
> > > > > On rawhide I got the warning on Fedora 41 don't but
> > > > > __cplusplus
> > > > > of GCC
> > > > > compiler is the same (201703)
> > > > > 
> > > > > My proposal is to change the comparison from 202002L to
> > > > > 201703L
> > > > > -#if GTEST_INTERNAL_CPLUSPLUS_LANG >= 202002L && \
> > > > > +#if GTEST_INTERNAL_CPLUSPLUS_LANG >= 201703L && \
> > > > 
> > > > That is not correct.  <version> is actually not guaranteed to
> > > > be
> > > > there for
> > > > C++17, it was only added in https://wg21.link/p0754r2 in 2018
> > > > (so
> > > > e.g. for
> > > > GCC since GCC 9.1).  __has_include is supported by GCC since
> > > > 2014
> > > > (so GCC
> > > > 5.1).  So your change would break building with GCC 5.1 to 8.5.
> > > > I think if it did e.g.
> > > > #if (GTEST_INTERNAL_CPLUSPLUS_LANG >= 202002L && \
> > > >      !defined(__has_include)) || \
> > > >      (GTEST_INTERNAL_CPLUSPLUS_LANG >= 201703L && \
> > > >       GTEST_INTERNAL_HAS_INCLUDE(<version>))
> > > > #include <version>
> > > > #endif
> > > > it would be better, C++20 should guarantee there is <version>
> > > > (but
> > > > also
> > > > that __has_include is there, but this stuff attempts to cover
> > > > also
> > > > the cases
> > > > of the incremental development of the standard features).
> > > > I don't really see the point of including <ciso646>, it is a
> > > > useless header
> > > > which doesn't contain anything since its introduction and has
> > > > been
> > > > removed
> > > > without deprecation in C++20.
> > > > I think the rationale some people give is that it is the
> > > > smallest
> > > > C++ header
> > > > (contains nothing) which still includes some basic header with
> > > > some
> > > > macros
> > > > (in the libstdc++ case it is <bits/c++config.h>, in libcxx case
> > > > it
> > > > is
> > > > <__config>).  But e.g. in the libstdc++ case, that header
> > > > doesn't
> > > > really
> > > > define any feature test macros, the __cpp_* macros are
> > > > predefined
> > > > by the
> > > > compiler and __cpp_lib_* are defined by the individual headers
> > > > which provide
> > > > that functionality or (when it exists) in <version>.
> > > 
> > > "Traditionally" <ciso646> was included to find out which C++
> > > standard
> > > library implementation you were using, by including it and then
> > > checking for _LIBCPP_VERSION or _GLIBCXX_VERSION.
> > > 
> > > So it's not supposed to be used for checking the standard
> > > __cpp_lib_xxx macros, but the implementation-specific ones.
> > > 
> > > N.B. GCC's <ciso646> did not actually define _GLIBCXX_VERSION (or
> > > any
> > > other libstdc++ macros) until GCC 6.1, because it really did
> > > _nothing_
> > > before that. It didn't even include <bits/c++config.h>.
> > > 
> > > I second Jakub's suggestion to just include <version> if it's
> > > available. It's not required by the C++ standard until C++20, but
> > > given a sufficiently new compiler the <version> header is still
> > > present and can be included for older versions of C++.
> > > 
> > 
> > Hi, but if we are build in an "old" GCC , can we replace  <ciso646>
> > by
> > <cerrno>  ? I also like the Jakub's suggestion [1] . Should/Can  we
> > apply this suggestion also to abseil-cpp-20240722.1 ?
> > 
> > [1]
> > #if GTEST_INTERNAL_HAS_INCLUDE(<version>) || \
> >     (GTEST_INTERNAL_CPLUSPLUS_LANG >= 202002L &&
> > !defined(__has_include))
> > #include <version>  // C++20 and later
> > #else
> > #include <cerrno>  // Pre-C++20
> > #endif
> 
> 
> I missed this follow-up question, sorry. Including <cerrno> would
> have
> equivalent effects to <ciso606>, except for also declaring all the
> contents of <errno.h> (which isn't very much, so mostly harmless).
> 
> Before GCC 6.1 <cerrno> did not define the _GLIBCXX_xxx macros, but
> neither did <ciso646> so there's no difference between then in that
> respect.
> 

OK,  I will check if maintainer of the package in question want apply
this solution 

IIRC, I disabled warnings being treated as errors ...

Thank you ,
-- 
Sérgio M. B.
-- 
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