[PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Ken Brown]

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;
 }
 
 extern "C" int
-- 
2.30.0

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Corinna Vinschen]

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.


Thanks,
Corinna

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Ken Brown]

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):

diff --git a/winsup/cygwin/resource.cc b/winsup/cygwin/resource.cc
index 9e39d3a04..ac56acf8c 100644
--- a/winsup/cygwin/resource.cc
+++ b/winsup/cygwin/resource.cc
@@ -182,10 +182,7 @@ getrlimit (int resource, struct rlimit *rlp)
           __get_rlimit_stack (rlp);
           break;
         case RLIMIT_NOFILE:
-         rlp->rlim_cur = getdtablesize ();
-         if (rlp->rlim_cur < OPEN_MAX)
-           rlp->rlim_cur = OPEN_MAX;
-         rlp->rlim_max = OPEN_MAX_MAX;
+         rlp->rlim_cur = rlp->rlim_max = OPEN_MAX_MAX;
           break;
         case RLIMIT_CORE:
           rlp->rlim_cur = cygheap->rlim_core;
diff --git a/winsup/cygwin/sysconf.cc b/winsup/cygwin/sysconf.cc
index 001da96ad..d5d82bb4a 100644
--- a/winsup/cygwin/sysconf.cc
+++ b/winsup/cygwin/sysconf.cc
@@ -21,15 +21,6 @@ details. */
  #include "cpuid.h"
  #include "clock.h"

-static long
-get_open_max (int in)
-{
-  long max = getdtablesize ();
-  if (max < OPEN_MAX)
-    max = OPEN_MAX;
-  return max;
-}
-
  static long
  get_page_size (int in)
  {
@@ -520,7 +511,7 @@ static struct
    {cons, {c:CHILD_MAX}},               /*   1, _SC_CHILD_MAX */
    {cons, {c:CLOCKS_PER_SEC}},          /*   2, _SC_CLK_TCK */
    {cons, {c:NGROUPS_MAX}},             /*   3, _SC_NGROUPS_MAX */
-  {func, {f:get_open_max}},            /*   4, _SC_OPEN_MAX */
+  {cons, {c:OPEN_MAX_MAX}},            /*   4, _SC_OPEN_MAX */
    {cons, {c:_POSIX_JOB_CONTROL}},      /*   5, _SC_JOB_CONTROL */
    {cons, {c:_POSIX_SAVED_IDS}},                /*   6, _SC_SAVED_IDS */
    {cons, {c:_POSIX_VERSION}},          /*   7, _SC_VERSION */

WDYT?

Ken

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Corinna Vinschen]

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?

One problem is that there are some applications in the wild which run
loops up to either sysconf(_SC_OPEN_MAX) or OPEN_MAX to handle open
descriptors.  tcsh is one of them.  It may slow done tcsh quite a bit
if the loop runs to 3200 now every time.


Corinna

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Corinna Vinschen]

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.


Corinna

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Ken Brown]

On 1/28/2021 11:07 AM, 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?

Makes sense to me.

> One problem is that there are some applications in the wild which run
> loops up to either sysconf(_SC_OPEN_MAX) or OPEN_MAX to handle open
> descriptors.  tcsh is one of them.  It may slow done tcsh quite a bit
> if the loop runs to 3200 now every time.

I don't use tcsh.  Is it easy to test this?

Ken

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Ken Brown]

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?

Thanks.

Ken

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Ken Brown]

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

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Corinna Vinschen]

On Jan 29 14:23, Ken Brown via Cygwin-patches wrote:
> On 1/28/2021 5:28 PM, Ken Brown via Cygwin-patches wrote:
> > > ...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?

Yes, that was the idea, kind of like a poor mans include/bits dir on
Linux...

> 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".

Sorry, I didn't mean to imply you will have to do that right away.
It was just a thought to move over more values in later patches.


Corinna

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Corinna Vinschen]

On Jan 28 15:33, Ken Brown via Cygwin-patches wrote:
> On 1/28/2021 11:07 AM, Corinna Vinschen via Cygwin-patches wrote:
> > One problem is that there are some applications in the wild which run
> > loops up to either sysconf(_SC_OPEN_MAX) or OPEN_MAX to handle open
> > descriptors.  tcsh is one of them.  It may slow done tcsh quite a bit
> > if the loop runs to 3200 now every time.
> 
> I don't use tcsh.  Is it easy to test this?

I just checked the source.  In the olden days, before the invention of
close-on-exec, tcsh closed all descriptors > 2 up to OPEN_MAX prior to
starting any executable.

With close-on-exec this happens only at startup and after an error
occured.

So testing should be easy: The tcsh startup may be noticably slower.


Corinna

Re: [PATCH] Cygwin: getdtablesize: always return OPEN_MAX_MAX

[Corinna Vinschen]

On Feb  1 10:50, Corinna Vinschen via Cygwin-patches wrote:
> On Jan 28 15:33, Ken Brown via Cygwin-patches wrote:
> > On 1/28/2021 11:07 AM, Corinna Vinschen via Cygwin-patches wrote:
> > > One problem is that there are some applications in the wild which run
> > > loops up to either sysconf(_SC_OPEN_MAX) or OPEN_MAX to handle open
> > > descriptors.  tcsh is one of them.  It may slow done tcsh quite a bit
> > > if the loop runs to 3200 now every time.
> > 
> > I don't use tcsh.  Is it easy to test this?
> 
> I just checked the source.  In the olden days, before the invention of
> close-on-exec, tcsh closed all descriptors > 2 up to OPEN_MAX prior to
> starting any executable.
> 
> With close-on-exec this happens only at startup and after an error
> occured.
> 
> So testing should be easy: The tcsh startup may be noticably slower.

I checked this right now and I don't see a noticable, i. .e, any,
difference.


Corinna