为什么 output 不在控制台中打印 output C++

Question

So I was running a simple C++ code containing this piece

freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
for(int k=i;k--;k>=1)
{
    if(outgoing[k]=='Y' && incoming[k-1]=='Y')
        result[i][k-1]='Y';
    else
        break;
}

So usually the error if there is any it printed into console output but while running this code it printed this error inside the output file

/home/keith/builds/mingw/gcc-9.2.0-mingw32-cross-native/mingw32/libstdc++-v3/include/bits/basic_string.h:1067:
 std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::reference
 std::__cxx11::basic_string<_CharT, _Traits,
 _Alloc>::operator[](std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>;
 std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::reference =
 char&; std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::size_type
 = unsigned int]: Assertion '__pos <= size()' failed.

I don't understand why? And who is Keith?

I know the error by the way here for(int k=i;k--;k>=1) k-- and k>=1 should be swapped

Answer 1

Whenever you are reading characters from a string or file, you have to make sure your loop ends before the string or file reaches \n or EOF .

This can be verified by the compiler only if you mention bounds for the string or file which is known to compiler.

So instead of running the loop until k>=1 maybe you can use a while loop or maybe str.length() where str is a string variable.

And maybe Keith is someone who was involved in writing the mingw compiler.