https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86138
Bug ID: 86138
Summary: C++17: getline(istream, string) crashes on Cygwin
because incompatible C++14 function is called
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: franke at computer dot org
Target Milestone: ---
The function std::getline(istream &, string &, char) crashes if build with
Cygwin gcc-g++-7.3.0-2 and -std=gnu++17 enabled.
This is because there is a bogus prototype specialization in basic_string.h:
template<>
basic_istream<char>&
getline(basic_istream<char>& __in, basic_string<char>& __str,
char __delim);
There is no implementation for this specialization. This has apparently the
same effect as the 'extern template' which is disabled for C++17 in
basic_string.tcc:
#if _GLIBCXX_EXTERN_TEMPLATE > 0 && __cplusplus <= 201402L
...
extern template
basic_istream<char>&
getline(basic_istream<char>&, string&, char);
...
#endif
As a consequence, no C++17 compatible code for this getline() is generated and
the old getline() from cygstdc++-6.dll is called instead.
AFAICS the above still holds for current SVN trunk release 261563.
For a testcase and a proposed patch see:
https://cygwin.com/ml/cygwin/2018-06/msg00125.html
