[cfe-dev] [libc++] Is namespace "index" a special kind of a namespace in libc++?

[Richard Smith via cfe-dev]

Looks like glibc provides it in <string.h> too if _GNU_SOURCE is defined,
which it *always* is when compiling in C++ mode (unless explicitly
undefined). :-(

Is it still the case that glibc requires _GNU_SOURCE to be defined in order
for it to provide the symbols that C++ compilation requires? A quick test
seems to show that _ISOC99_SOURCE (or sometimes _ISOC11_SOURCE) is actually
sufficient. Perhaps we should provide a mode that doesn't define
_GNU_SOURCE (ideally, -std=c++XX would have that effect, but that's
probably going to break too much).

On 29 October 2017 at 13:14, Richard Smith <richard at metafoo.co.uk> wrote:

> There is a ::index function in strings.h on some platforms that might be
> leaking into <algorithm>.
>
> On 29 Oct 2017 13:10, "Klemen Forstnerič via cfe-dev" <
> cfe-dev at lists.llvm.org> wrote:
>
> Hi libc++ developers,
>
> I'm having a problem compiling the following code:
>
> Header (index.hpp):
>
> #ifndef INDEX_HPP_
> #define INDEX_HPP_
>
> #include <algorithm>
>
> namespace index {
>
> class Index {
>  public:
>   Index();
> };
>
> }
>
> #endif // INDEX_HPP_
>
> Source (index.cpp):
>
> #include "index.hpp"
>
> namespace index {
>
> Index::Index() {
> }
>
> }
>
> These are the errors I get:
>
> index.cpp:5:1: error: use of undeclared identifier 'Index'; did you mean
> '::index::Index'?
> Index::Index() {
> ^~~~~
> ::index::Index
> ./index.hpp:8:7: note: '::index::Index' declared here
> class Index {
>       ^
> index.cpp:5:8: error: cannot define or redeclare 'Index' here because
> namespace 'index' does not enclose namespace 'Index'
> Index::Index() {
> ~~~~~~~^
> 2 errors generated.
>
> This is my compile command:
> clang++ --stdlib=libc++ index.cpp
>
> clang version:
> clang version 5.0.0 (tags/RELEASE_500/final)
> Target: x86_64-unknown-linux-gnu
> Thread model: posix
> InstalledDir: /usr/local/bin
>
> libc++ version is today's trunk
>
> System: Linux trusty64 3.16.0-55-generic #74~14.04.1-Ubuntu SMP Tue Nov 17
> 10:15:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
>
>
> If I don't include <algorithm> or if I change the name of the namespace to
> something other than "index", the code compiles.
>
> Is this a libc++ bug?
>
> Cheers,
> Klemen
>
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>
>
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