[libcxx] r309474 - [libc++] Hoist extern template above first use

[Hans Wennborg via cfe-commits]

Sounds good to me, but Eric or Marshall need to sign off.

On Thu, Aug 3, 2017 at 10:15 AM, Shoaib Meenai <smeenai at fb.com> wrote:
> Ping.
>
> On 7/28/17, 7:57 PM, "Shoaib Meenai" <smeenai at fb.com> wrote:
>
>     Marshall, Eric, Hans,
>
>     Any objections to backporting this to 5.0? It fixes a potential visibility
>     issue for clients of the header.
>
>     On 7/28/17, 7:54 PM, "cfe-commits on behalf of Shoaib Meenai via cfe-commits" <cfe-commits-bounces at lists.llvm.org on behalf of cfe-commits at lists.llvm.org> wrote:
>
>         Author: smeenai
>         Date: Fri Jul 28 19:54:41 2017
>         New Revision: 309474
>
>         URL: https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D309474-26view-3Drev&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=EcGbIxegCOTbSLMJelp_vOaeGiS_iQ1eciM_oeX41-E&s=5q7TS5mhaUsf-1jQBqX62RvjcqAiy2whh8RO7yFhPyA&e=
>         Log:
>         [libc++] Hoist extern template above first use
>
>         This function template is referenced inside class basic_string as a
>         friend function. The extern template declaration needs to be above that
>         friend declaration to actually take effect.
>
>         This is important because this function was marked as exported in
>         r307966, so without the extern template taking effect, it can leak into
>         other DSOs as a visible symbol.
>
>         Modified:
>             libcxx/trunk/include/string
>
>         Modified: libcxx/trunk/include/string
>         URL: https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_libcxx_trunk_include_string-3Frev-3D309474-26r1-3D309473-26r2-3D309474-26view-3Ddiff&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=EcGbIxegCOTbSLMJelp_vOaeGiS_iQ1eciM_oeX41-E&s=zFJXc9CA6Sgyh25kGeAh4Qo36gpNQX_zo2qRlRFJoL8&e=
>         ==============================================================================
>         --- libcxx/trunk/include/string (original)
>         +++ libcxx/trunk/include/string Fri Jul 28 19:54:41 2017
>         @@ -556,6 +556,8 @@ template<class _CharT, class _Traits, cl
>          basic_string<_CharT, _Traits, _Allocator>
>          operator+(const basic_string<_CharT, _Traits, _Allocator>& __x, _CharT __y);
>
>         +_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS string operator+<char, char_traits<char>, allocator<char> >(char const*, string const&))
>         +
>          template <bool>
>          class _LIBCPP_TEMPLATE_VIS __basic_string_common
>          {
>         @@ -3999,7 +4001,6 @@ basic_string<_CharT, _Traits, _Allocator
>
>          _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<char>)
>          _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<wchar_t>)
>         -_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS string operator+<char, char_traits<char>, allocator<char> >(char const*, string const&))
>
>          #if _LIBCPP_STD_VER > 11
>          // Literal suffixes for basic_string [basic.string.literals]
>
>
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>
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>
>