[Bug libstdc++/58393] New: Please relax feature check for std::to_string and std::sto* for uClibc

[Bug libstdc++/58393] New: Please relax feature check for std::to_string and std::sto* for uClibc

[nicolas.cavallari at lri dot fr]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58393

            Bug ID: 58393
           Summary: Please relax feature check for std::to_string and
                    std::sto* for uClibc
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nicolas.cavallari at lri dot fr

Created attachment 30800
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30800&action=edit
Relax constraints on std::to_w?string and std:sto*

The GCC build system's feature check that must be passed to enable support for
std::to_w?string and std::sto.* asks for the underlying C library to support a
large set of C99 functions, including C99 real and complex math.

uClibc does not implement complex math function and the C99 real math functions
are optional.

The implementation of std::to_w?string and std::sto.* do not use complex math
functions and probably never will, so it is a bit sad that a libstdc++ built
against uClibc does not provide std::to_w?string and std::sto.*

The feature check should be relaxed to only requires the functions that are
actually used to implement std::to_w?string and std::sto.*

The attached patch is an example of how it could be done.

[Bug libstdc++/58393] Please relax feature check for std::to_string and std::sto* for uClibc

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58393

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> ---
In any case, please send patches to the mailing list, attached to bug report
will be easily overlooked. More specifically, if we are going to be more fine
grained about C99 support, other headers have to be consistently updated.

[Bug libstdc++/58393] Please relax feature check for std::to_string and std::sto* for uClibc

[thomas.petazzoni@free-electrons.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58393

Thomas Petazzoni <thomas.petazzoni@free-electrons.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |thomas.petazzoni@free-elect
                   |                            |rons.com

--- Comment #2 from Thomas Petazzoni <thomas.petazzoni@free-electrons.com> ---
I am one of the core developers of Buildroot, an embedded Linux build system,
which offers amongst other choices, the possibility of building a Linux system
based on the uClibc library. As such, we are facing the same problem as the one
reported by Nicolas Cavallari in this bug report: uClibc doesn't implement the
C99 complex maths functions, and this prevents libstdc++ from providing many
std-c++11 methods that are clearly unrelated to complex maths.

Has any progress been made towards applying Nicolas's patch?

[Bug libstdc++/58393] Please relax feature check for std::to_string and std::sto* for uClibc

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58393

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-07-02
                 CC|                            |redi at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
No, but I do want to improve the use of those macros, and fix other issues like
PR 11196 at the same time.

[Bug libstdc++/58393] Please relax feature check for std::to_string and std::sto* for uClibc

[nicolas.cavallari at lri dot fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58393

nicolas.cavallari at lri dot fr changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #30800|0                           |1
        is obsolete|                            |

--- Comment #4 from nicolas.cavallari at lri dot fr ---
Created attachment 33060
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33060&action=edit
7 patches for being more specific with feature checks, in mbox format.

Following Paolo's comment, i made some other patches a while ago, using more
specific feature checks everywhere.  The only part where _GLIBCXX_USE_C99 is
still needed is when determining whether the time functions allows one or two
leap seconds.

However, my attemps to run the testsuite were always met with frustration and
undeterministic results, so i delayed it and kept working around the problem in
my programs.

I attach my untested patches here. Maybe i'll fight with the testsuite again,
maybe not.