[Issue 18309] New: std.process.pipeProcess should warn if the buffer is full

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18309

          Issue ID: 18309
           Summary: std.process.pipeProcess should warn if the buffer is
                    full
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Linux
            Status: NEW
          Severity: major
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: greensunny12 at gmail.com

This program never terminates:


```
void main(string[] args)
{
    import std.process, std.stdio;
    "starting".writeln;
    auto pipes = pipeProcess(["seq", "13000"], Redirect.stdout); // set me to
12k to work
    while(true) {
                auto res = tryWait(pipes.pid);
                if (res.terminated) break;
    }
    foreach (c; pipes.stdout.byChunk(100)) {
        writeln(cast(string) c);
        break;
     }
    "finished".writeln;
}
```

This is due to pipe's buffer (PIPE_BUF) being exceeded.

http://man7.org/linux/man-pages/man2/pipe.2.html

Of course, the solution is to read from the pipe in the loop, but I feel like
this is still something that's very easy to run into.

Not sure whether that's something that can/should be done by the library code,
or it should simply be documented better.

--