[RFC] PR5820: two CTRL-D are not enough?!?

[Paolo Carlini]

Hi,

this is one of weirdest PR I have seen in the last months and I have no 
idea if the current behaviour of v3 is conforming or not in this respect.

Submitter maintains that usually two CTRL-D indicates end of output, 
whereas v3 needs /four/.
This is the original testcase:

#include <iostream>

int main()
{
   int i;
   char c;
   
   std::cout << "Enter an integer: ";
   std::cin >> i;
   if (!std::cin) {
     std::cerr << "Unexpected read problem\n";
     return 1;
   }   
   std::cout << '\n' << "std::cin.eof()=" << std::cin.eof() << '\n';
   std::cout << "The number was: " << i << '\n';
   std::cin >> c;
   if (std::cin) {
     std::cerr << "Could read " << c << " after the number!\n";
   }   
}

I have confirmed that this happens on linux and the following is an 
excerpt of a trace (after a "5" I had to press CTRL-D four times):

...

SYS_197(0, 0xbffff610, 0, 0xbffff610, 0) = 0
ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) 
= 0x400c6000
read(0, "5", 4096)                      = 1
_llseek(0, -1, 0xbffff550, SEEK_CUR)    = -1 ESPIPE (Illegal seek)
_llseek(0, 0, 0xbffff550, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
_llseek(0, 1, 0xbffff410, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
_llseek(0, 0, 0xbffff410, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
read(0, "", 4096)                       = 0
_llseek(0, 1, 0xbffff420, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
_llseek(0, 0, 0xbffff420, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
read(0, "", 4096)                       = 0
_llseek(0, 1, 0xbffff420, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
_llseek(0, 0, 0xbffff420, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
read(0, "", 4096)                       = 0
write(1, "\n", 1)                       = 1

...

In fact, the same testcase compiled by icc is not affected by the 
"problem"...

Opinions?

Ciao, Paolo.