Bug#897373: libc6: feof(file) always false when forking after read

[Florian Weimer <fw@deneb.enyo.de>]

* David Beniamine:

> On Thu, May 10, 2018 at 07:06:03PM +0200, Florian Weimer wrote:
>> * David Beniamine:
>> 
>> > int do_fork() {
>> >     pid_t pid;
>> >
>> >     switch (pid = fork()) {
>> >         case -1:
>> >             fprintf(stderr, "Fork failed\n");
>> >             return -1;
>> >         case 0:
>> >             exit(-1);
>> 
>> Does the issue go away when you call _exit instead of exit?
>> 
> It goes away with _exit, indeed.

According to POSIX, exit is required to flush all streams, and fflush
is required to reset the position of the underlying file descriptor
(more precisely, the open file description) to the current read
position.  That affects the descriptor in the parent, too.  I'm not
sure if this is actually a glibc bug.