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
