On 1/28/2021 5:28 PM, Ken Brown via Cygwin-patches wrote:
On 1/28/2021 11:13 AM, Corinna Vinschen via Cygwin-patches wrote:
On Jan 28 17:07, Corinna Vinschen via Cygwin-patches wrote:
On Jan 28 08:42, Ken Brown via Cygwin-patches wrote:
On 1/28/2021 5:20 AM, Corinna Vinschen via Cygwin-patches wrote:
On Jan 27 21:51, Ken Brown via Cygwin-patches wrote:
According to the Linux man page for getdtablesize(3), the latter is
supposed to return "the maximum number of files a process can have
open, one more than the largest possible value for a file descriptor."
The constant OPEN_MAX_MAX is the only limit enforced by Cygwin, so we
now return that.
Previously getdtablesize returned the current size of cygheap->fdtab,
Cygwin's internal file descriptor table. But this is a dynamically
growing table, and its current size does not reflect an actual limit
on the number of open files.
With this change, gnulib now reports that getdtablesize and
fcntl(F_DUPFD) work on Cygwin. Packages like GNU tar that use the
corresponding gnulib modules will no longer use gnulib replacements on
Cygwin.
---
winsup/cygwin/syscalls.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index 5da05b18a..1f16d54b9 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -2887,7 +2887,7 @@ setdtablesize (int size)
extern "C" int
getdtablesize ()
{
- return cygheap->fdtab.size;
+ return OPEN_MAX_MAX;
}
getdtablesize is used internally, too. After this change, the values
returned by sysconf and getrlimit should be revisited as well.
They will now return OPEN_MAX_MAX, as I think they should. The only
question in my mind is whether to simplify the code by removing the calls to
getdtablesize, something like this (untested):
But then again, what happens with OPEN_MAX in limits.h? Linux removed
it entirely. Given we have such a limit and it's not flexible as on
Linux, should we go ahead, drop OPEN_MAX_MAX entirely and define
OPEN_MAX as 3200?
...ideally by adding a file include/cygwin/limits.h included by
include/limits.h, which defines __OPEN_MAX et al, as required.
I'm not completely sure I follow. Do you mean include/cygwin/limits.h should
contain
#define __OPEN_MAX 3200
and include/limits.h should contain
#define OPEN_MAX __OPEN_MAX ?
For the sake of my education, could you explain the reason for this?
Trying to answer my own question, I guess the idea is to hide implementation
details from viewers of limits.h. Is that right? I took a stab at this and am
about to send a patchset. I'm not sure whether I made a reasonable choice of
"et al" in "__OPEN_MAX et al".
Ken
