Package: liblua5.1-posix1
Version: 5.1.2-3
Severity: normal
How to reproduce:
[isbear:~] cat one
adsf
fasdfea adf
fdasfeaf
fdaaaffff
fdag
fdasffffasddf
[isbear:~] cat luatest2.lua
-- pipe
require ( 'posix' )
f = io.popen ( 'cat one' )
c = 10
while c > 0 do
c = c - 1
ret = posix.rpoll ( f, 500 )
lin = nil
-- if ret == 1 then
lin = f:read ()
-- end
print ( ret, lin )
end
-- The End.
[isbear:~] lua luatest2.lua
nil adsf
nil fasdfea adf
nil fdasfeaf
nil fdaaaffff
nil fdag
nil fdasffffasddf
nil
nil nil
nil nil
nil nil
As we see, rpoll returns nil on successfully opened pipe. Though, there
are even more amazing example:
[isbear:~] cat luatest3.lua
-- pipe with delay
require ( 'posix' )
f = io.popen ( 'sleep 1 ; cat one' )
c = 10
while c > 0 do
c = c - 1
ret = posix.rpoll ( f, 500 )
lin = nil
if ( ret == 1 ) then
lin = f:read ()
end
print ( ret, lin )
end
-- The End.
[isbear:~] lua luatest3.lua
0 nil
0 nil
1 adsf
nil nil
nil nil
nil nil
nil nil
nil nil
nil nil
nil nil
rpoll's behaviour looks strange, isn't it?
No any error messages
How it is expected to be
There is corresponding code snippet from lposix.c:
/* from http://lua-users.org/lists/lua-l/2007-11/msg00346.html */
static int Ppoll(lua_State *L) /** poll(filehandle, timeout) */
{
struct pollfd fds;
FILE* file = *(FILE**)luaL_checkudata(L,1,LUA_FILEHANDLE);
int ret,timeout = luaL_checkint(L,2);
fds.fd = fileno(file);
fds.events = POLLIN;
ret = poll(&fds,1,timeout);
if (ret == -1) {
lua_error(L);
}
if (ret == 1 && ((fds.revents & POLLHUP) || (fds.revents & POLLNVAL))) {
lua_pushnil(L);
} else {
lua_pushnumber(L,ret);
}
return 1;
}
I'll use next simple C program to demonstrate what is going behind the
scenes:
[isbear:~] cat poll.c
#include <poll.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
int main ( int argc, char **argv )
{
int ret;
struct pollfd fds;
char a[10];
int c = 10;
switch ( *argv[1] ) {
case 'p':
fds.fd = fileno ( popen ( argv[2], "r" ) );
break;
case 'f':
fds.fd = open ( argv[2], O_RDONLY );
break;
default:
fds.fd = fileno ( stdin );
break;
}
fds.events = POLLIN;
printf ( "file number: %d\n", fds.fd );
printf ( "(POLLIN %X, POLLPRI %X, POLLOUT %X, POLLERR %X,"
" POLLHUP %X, POLLNVAL %X)\n",
POLLIN, POLLPRI, POLLOUT, POLLERR, POLLHUP, POLLNVAL );
do {
ret = poll ( &fds, 1, 400 );
printf ( "Poll: %d, revents: %X", ret, fds.revents );
if ( ret ) {
int num = read ( fds.fd, a, 9 );
printf ( ", read: %d", num );
}
puts ("");
sleep ( 1 );
} while ( c-- > 0 );
}
/* The End. */
[isbear:~] gcc poll.c
[isbear:~] ./a.out f 'one'
file number: 3
(POLLIN 1, POLLPRI 2, POLLOUT 4, POLLERR 8, POLLHUP 10, POLLNVAL 20)
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 2
Poll: 1, revents: 1, read: 0
Poll: 1, revents: 1, read: 0
Poll: 1, revents: 1, read: 0
Poll: 1, revents: 1, read: 0
[isbear:~] ./a.out p 'cat one'
file number: 3
(POLLIN 1, POLLPRI 2, POLLOUT 4, POLLERR 8, POLLHUP 10, POLLNVAL 20)
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 2
Poll: 1, revents: 10, read: 0
Poll: 1, revents: 10, read: 0
Poll: 1, revents: 10, read: 0
Poll: 1, revents: 10, read: 0
[isbear:~] ./a.out p 'sleep 1; cat one; sleep 3'
file number: 3
(POLLIN 1, POLLPRI 2, POLLOUT 4, POLLERR 8, POLLHUP 10, POLLNVAL 20)
Poll: 0, revents: 0
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 1, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 9
Poll: 1, revents: 11, read: 2
Poll: 1, revents: 10, read: 0
Poll: 1, revents: 10, read: 0
Poll: 1, revents: 10, read: 0
so, when pipe command finishes (but data are still available), poll
sets POLLHUP, and rpoll then returns nil.
man 2 poll says:
POLLHUP
Hang up (output only).
POLLNVAL
Invalid request: fd not open (output only).
So, these flags are relative to output, not to input (as we claimed in
fds.events, we interested only in input events). IMHO, these flags
should be ignored.
When I added patch below and rebuilt package, all works fine.
--- lua-posix-5.1.2.a/posix.c 2008-01-29 14:54:24.000000000 +0200
+++ lua-posix-5.1.2/lposix.c 2008-07-18 03:39:39.000000000 +0300
@@ -495,11 +495,11 @@
if (ret == -1) {
lua_error(L);
}
- if (ret == 1 && ((fds.revents & POLLHUP) || (fds.revents & POLLNVAL))) {
+/* if (ret == 1 && ((fds.revents & POLLHUP) || (fds.revents & POLLNVAL))) {
lua_pushnil(L);
- } else {
+ } else {*/
lua_pushnumber(L,ret);
- }
+/* } */
return 1;
}
Reportbug output:
-- System Information:
Debian Release: lenny/sid
APT prefers testing
APT policy: (500, 'testing'), (50, 'unstable')
Architecture: i386 (i686)
Kernel: Linux 2.6.24-1-686 (SMP w/1 CPU core)
Locale: LANG=uk_UA.UTF-8, LC_CTYPE=uk_UA.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash
Versions of packages liblua5.1-posix1 depends on:
ii libc6 2.7-10 GNU C Library: Shared libraries
liblua5.1-posix1 recommends no packages.
-- no debconf information
--
Михайло Даниленко
-------------------------------
jabber: <[EMAIL PROTECTED]>
icq: 200352743
--
To UNSUBSCRIBE, email to [EMAIL PROTECTED]
with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
