On Sun, 19 Jun 2022 15:08:19 -0400
Ken Brown wrote:
> Consider the following program, which reads from standard input a line at a
> time
> and then echoes the input back to the terminal:
>
> $ cat cat_line.c
> #include <stdio.h>
>
> int main ()
> {
> char buf[BUFSIZ];
>
> while (fgets (buf, BUFSIZ, stdin))
> fputs (buf, stdout);
> }
>
> Run the program, type one or more characters (without hitting Enter), and
> type
> Ctrl-d until the program exits. What I expect is that nothing visible
> happens
> on the first Ctrl-d [but the input is sent to the internal stdin buffer], and
> that the input is echoed and the program exits after the second Ctrl-d [the
> program sees EOF]. This is what happens on Linux. On Cygwin, however, the
> program keeps running after the second Ctrl-d and doesn't exit until Ctrl-d
> is
> pressed a third time.
>
> I observed this problem because of a failing Emacs test, in which the program
> "rev" was not seeing EOF after being sent Ctrl-d; "rev" does something like
> the
> test case above, but using fgetws instead of fgets.
Isn't this a bug of newlib? Try following code.
#include <stdio.h>
int main()
{
printf("%d\n", getchar());
printf("%d\n", feof(stdin));
printf("%d\n", getchar());
return 0;
}
If you press Ctrl-D at the first getchar(), the second getchar()
does not return EOF while it does in linux.
The following patch seems to resolve the issue.
diff --git a/newlib/libc/stdio/refill.c b/newlib/libc/stdio/refill.c
index ccedc7af7..843163b7e 100644
--- a/newlib/libc/stdio/refill.c
+++ b/newlib/libc/stdio/refill.c
@@ -47,11 +47,9 @@ __srefill_r (struct _reent * ptr,
fp->_r = 0; /* largely a convenience for callers */
-#ifndef __CYGWIN__
/* SysV does not make this test; take it out for compatibility */
if (fp->_flags & __SEOF)
return EOF;
-#endif
/* if not already reading, have to be reading and writing */
if ((fp->_flags & __SRD) == 0)
However, I am not sure what this #ifndef __CYGWIN__ is for.
--
Takashi Yano <takashi.y...@nifty.ne.jp>
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