When deduction guides are supported by the compiler (i.e. for C++17 and
later) replace two basic_string constructors by constrained function
templates as required by LWG 3075. In order to ensure that the pre-C++17
non-template constructors are still exported from the shared library
define a macro in src/c++11/string-inst.cc to force the non-template
declarations (this isn't strictly needed yet, because the string
instantiations are compiled with -std=gnu++11, but that is likely to
change).
LWG 3076 basic_string CTAD ambiguity
* doc/xml/manual/intro.xml: Document LWG 3076 change.
* include/bits/basic_string.h
[__cpp_deduction_guides && !_GLIBCXX_DEFINING_STRING_INSTANTIATIONS]
(basic_string(const _CharT*, const _Alloc&)): Turn into a function
template constrained by _RequireAllocator.
(basic_string(size_type, _CharT, const _Alloc&)): Likewise.
* src/c++11/string-inst.cc (_GLIBCXX_DEFINING_STRING_INSTANTIATIONS):
Define.
* testsuite/21_strings/basic_string/cons/char/deduction.cc: Test
deduction
* testsuite/21_strings/basic_string/cons/wchar_t/deduction.cc:
Likewise.
From-SVN: r261670
