On Mon, Feb 16, 2015 at 9:46 PM, Paul Eggert <egg...@cs.ucla.edu> wrote:
> The other patches (after your revisions) look good and I installed them, but
> this one didn't look right. That part of the code really is intended to be
> used only on Cygwin and it's not portable to other platforms (e.g., it
> mishandles RLIM_SAVED_MAX). I suppose we could get it to work on Android
> too but let's not bother. Instead, let's not use Android's getdtablesize
> since it's obsolescent.
>
> I installed the attached patch instead, which I hope solves the problem in a
> different way. Please let me know whether it works on Android.
On Android, sysconf (_SC_OPEN_MAX) always returns the constant
OPEN_MAX (256). So if `ulimit -n` is not exactly 256,
test-{dup2,fcntl,getdtablesize} all fail because they think the OS
should have stopped them from using file descriptor 256.
Android behavior: (android-21, arm 32-bit)
# /shared/tmp/fdtest
rlimit: 1024
sysconf: 256
getdtablesize: 1024
Ubuntu/glibc behavior:
$ /tmp/fdtest
rlimit: 32768
sysconf: 32768
getdtablesize: 32768
Test program:
#include <unistd.h>
#include <stdio.h>
#include <sys/time.h>
#include <sys/resource.h>
int main(int argc, char **argv)
{
struct rlimit lim;
if (getrlimit (RLIMIT_NOFILE, &lim) == 0)
printf("rlimit: %d\n", (int)lim.rlim_cur);
printf("sysconf: %ld\n", sysconf (_SC_OPEN_MAX));
printf("getdtablesize: %d\n", getdtablesize());
return 0;
}
FWIW, the deprecated Bionic getdtablesize() function is implemented as:
// This was removed from POSIX 2004.
extern "C" int getdtablesize() {
struct rlimit r;
if (getrlimit(RLIMIT_NOFILE, &r) < 0) {
return sysconf(_SC_OPEN_MAX);
}
return r.rlim_cur;
}
