GCC 7.3.0 -std=gnu++17 failed to getline() from std::ifstream
Wed Jun 13 08:49:00 GMT 2018
On 6/12/2018 7:11 PM, Christian Franke wrote:
> Ivan Shynkarenka wrote:
> 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
> 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
> Â /usr/lib/gcc/*-pc-cygwin/7.3.0/include/c++/bits/basic_string.h
> fixes this.
for the investigation.
It seems an upstream bug so could you report it there ?
There are several c++17 bugs around
that is probably the reason why gcc 7.x defaults to c++14
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