Ivan Shynkarenka wrote:
I use x64 bit Cygwin and it failed in my home, work and Appveyor. I add
cygcheck.out with my environment.
I'm sorry about misspell prefix space in my prev example. Please try the
following one:
#include <fstream>
#include <iostream>
int main(int argc, char** argv)
{
std::string line;
std::ifstream stream("test.cpp");
while (getline(stream, line))
std::cout << line << std::endl;
return 0;
}
g++ -std=gnu++17 test.cpp
Could reproduce this with 32 and 64 bit Cygwin g++ 7.3.0
A comparison of preprocessor (-E) outputs shows that the "extern
template" declarations for getline() are only visible for C++ <= 14.
These are guarded by "__cplusplus <= 1402" in basic_string.tcc. This
should tell the compiler to generate new code for getline() if C++17 is
enabled instead of calling the (now incompatible) function in
cygstdc++-6.dll.
A comparison of assembly (-S) outputs shows that this does not work: If
C++17 is enabled, the compiler correctly generates local code for
getline(istream &, string &) but this code calls an external
getline(istream &, string &, char). Then the linker generates a call to
this getline() in cygstdc++-6.dll.
This is because there is a bogus prototype specialization for
getline(istream &, string &, char) in basic_string.h but no
corresponding implementation in basic_string.tcc. This has apparently an
equivalent effect as 'extern template'.
The attached patch for
/usr/lib/gcc/*-pc-cygwin/7.3.0/include/c++/bits/basic_string.h
fixes this.
Christian
--- basic_string.h.orig 2018-05-03 06:22:46.000000000 +0200
+++ basic_string.h 2018-06-12 15:56:03.215179300 +0200
@@ -6329,18 +6329,6 @@
{ return std::getline(__is, __str); }
#endif
- template<>
- basic_istream<char>&
- getline(basic_istream<char>& __in, basic_string<char>& __str,
- char __delim);
-
-#ifdef _GLIBCXX_USE_WCHAR_T
- template<>
- basic_istream<wchar_t>&
- getline(basic_istream<wchar_t>& __in, basic_string<wchar_t>& __str,
- wchar_t __delim);
-#endif
-
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
--
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