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Re: [GCC] C++ program calling std::getline() crashes with certain compilation flags




> The following C++ program crashes when compiled with GCC (both 5.4 and 6.3) under Cygwin, when compiled with both an optimization level higher than -O0 (i.e. -O1, -O2 or -O3) and the C++ standard set to -std=c++nn (for any supported nn, i.e. 98, 03, 11, 14 or 17):
> ```
> #include <iostream>
> #include <string>
> int main()
> {
>     std::string s;
>     std::getline(std::cin, s);
>     std::cout << "You entered \"" << s << "\".\n";
>     return 0;
> }
> ```
> On the other hand, when compiled with -std=gnu++nn or -O0, the program executes normally. For details, run the attached Bash script test_getline.sh, which produces the output contained in the attached file test_getline_Cygwin.txt . No similar problem shows with GCC under Linux.
> It looks similar to the problem reported in https://cygwin.com/ml/cygwin/2017-07/msg00088.html which appears to be circumvented by passing -std=gnu++11 instead of -std=c++11.

I've tried it with both cygwin-devel-2.8.0-1 and cygwin-devel-2.8.1-1.
With cygwin-devel-2.8.1-1, reproduced.
With cygwin-devel-2.8.0-1, there is no problem.

I've attached the script that I used and the results.

Attachment: test_getline.sh
Description: Binary data

CYGWIN_NT-10.0 Z87EXTREAM4 2.8.1(0.312/5/3) 2017-07-03 14:11 x86_64 Cygwin
base-cygwin                                   3.8-1
cygwin                                        2.8.1-1
cygwin-debuginfo                              2.8.1-1
cygwin-devel                                  2.8.0-1
g++ (GCC) 5.4.0
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

### -std=c++98 -O0 ###: You entered "// Let's see if it works...".
### -std=c++98 -O1 ###: You entered "// Let's see if it works...".
### -std=c++98 -O2 ###: You entered "// Let's see if it works...".
### -std=c++98 -O3 ###: You entered "// Let's see if it works...".
### -std=c++03 -O0 ###: You entered "// Let's see if it works...".
### -std=c++03 -O1 ###: You entered "// Let's see if it works...".
### -std=c++03 -O2 ###: You entered "// Let's see if it works...".
### -std=c++03 -O3 ###: You entered "// Let's see if it works...".
### -std=c++11 -O0 ###: You entered "// Let's see if it works...".
### -std=c++11 -O1 ###: You entered "// Let's see if it works...".
### -std=c++11 -O2 ###: You entered "// Let's see if it works...".
### -std=c++11 -O3 ###: You entered "// Let's see if it works...".
### -std=c++14 -O0 ###: You entered "// Let's see if it works...".
### -std=c++14 -O1 ###: You entered "// Let's see if it works...".
### -std=c++14 -O2 ###: You entered "// Let's see if it works...".
### -std=c++14 -O3 ###: You entered "// Let's see if it works...".
### -std=c++17 -O0 ###: You entered "// Let's see if it works...".
### -std=c++17 -O1 ###: You entered "// Let's see if it works...".
### -std=c++17 -O2 ###: You entered "// Let's see if it works...".
### -std=c++17 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++98 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++98 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++98 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++98 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O3 ###: You entered "// Let's see if it works...".
CYGWIN_NT-10.0 Z87EXTREAM4 2.8.1(0.312/5/3) 2017-07-03 14:11 x86_64 Cygwin
base-cygwin                                   3.8-1
cygwin                                        2.8.1-1
cygwin-debuginfo                              2.8.1-1
cygwin-devel                                  2.8.1-1
g++ (GCC) 5.4.0
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

### -std=c++98 -O0 ###: You entered "// Let's see if it works...".
### -std=c++98 -O1 ###: ./test_getline.sh: line 19: 20748 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++98 -O2 ###: ./test_getline.sh: line 19: 25148 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++98 -O3 ###: ./test_getline.sh: line 19:  8540 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++03 -O0 ###: You entered "// Let's see if it works...".
### -std=c++03 -O1 ###: ./test_getline.sh: line 19: 16156 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++03 -O2 ###: ./test_getline.sh: line 19: 12172 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++03 -O3 ###: ./test_getline.sh: line 19:   160 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++11 -O0 ###: You entered "// Let's see if it works...".
### -std=c++11 -O1 ###: ./test_getline.sh: line 19: 24840 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++11 -O2 ###: ./test_getline.sh: line 19: 12008 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++11 -O3 ###: ./test_getline.sh: line 19:  8140 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++14 -O0 ###: You entered "// Let's see if it works...".
### -std=c++14 -O1 ###: ./test_getline.sh: line 19:  7376 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++14 -O2 ###: ./test_getline.sh: line 19: 18080 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++14 -O3 ###: ./test_getline.sh: line 19: 22692 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++17 -O0 ###: You entered "// Let's see if it works...".
### -std=c++17 -O1 ###: ./test_getline.sh: line 19:  5796 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++17 -O2 ###: ./test_getline.sh: line 19: 24008 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=c++17 -O3 ###: ./test_getline.sh: line 19:  2844 Aborted (core dumped) ./test_getline < test_getline.cxx
### -std=gnu++98 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++98 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++98 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++98 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++03 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++11 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++14 -O3 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O0 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O1 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O2 ###: You entered "// Let's see if it works...".
### -std=gnu++17 -O3 ###: You entered "// Let's see if it works...".

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