Den 2011-04-18 13:43 skrev Peter Rosin:
> Hi!
>
> Using the following STC, I'm seeing what appears to be a memory
> leak in select(2).
>
> ----------------8<---(selectleak.c)---------
> #include <sys/time.h>
> #include <fcntl.h>
> #include <stdlib.h>
>
> int
> main(void)
> {
> fd_set fdset;
> struct timeval tv;
>
> long flags = fcntl(0, F_GETFL);
> fcntl(0, F_SETFL, flags | O_NONBLOCK);
>
> for (;;) {
> int res;
> char buf[20];
>
> FD_ZERO(&fdset);
> FD_SET(0, &fdset);
> tv.tv_sec = 1;
> tv.tv_usec = 0;
> res = select(1, &fdset, NULL, NULL, &tv);
> if (res < 0)
> exit(1);
> if (!res)
> continue;
> res = read(0, buf, sizeof(buf));
> if (res < 0)
> exit(1);
> }
>
> return 0;
> }
> ----------------8<--------------------------
>
> $ gcc -o selectleak selectleak.c
> $ cat /dev/zero | ./selectleak
>
> Note that "./selectleak < /dev/zero" does not trigger the leak for me (I
> haven't
> seen the memory usage go up, so at least not as reliably).
>
> An "strace -m malloc,select" has this:
>
> 156 59281 [main] selectleak 8440 cygwin_select: 1, 0x23CCFC, 0x0, 0x0, 0x0
> 64 59345 [main] selectleak 8440 calloc: (1, 44) = 49AF58, called by
> 61002389
> 63 59408 [main] selectleak 8440 calloc: (1, 12) = 49B018, called by
> 61002389
> 111 59519 [main] selectleak 8440 cygwin_select: to NULL, ms FFFFFFFF
> 62 59581 [main] selectleak 8440 cygwin_select: sel.always_ready 0
> 138 59719 [select_pipe] selectleak 8440 peek_pipe: , ready for read:
> avail 130892
> 160 59879 [main] selectleak 8440 select_stuff::wait: woke up. wait_ret
> 1. verifying
> 57 59936 [main] selectleak 8440 set_bits: me 0x49AF58, testing fd 0 ()
> 62 59998 [main] selectleak 8440 set_bits: ready 1
> 62 60060 [main] selectleak 8440 select_stuff::wait: gotone 1
> 61 60121 [main] selectleak 8440 select_stuff::wait: returning 0
> 61 60182 [main] selectleak 8440 select_stuff::cleanup: calling cleanup
> routines
> 104 60286 [main] selectleak 8440 free: (0x49B018), called by 0x610BC1EA
> 65 60351 [main] selectleak 8440 peek_pipe: , already ready for read
> 62 60413 [main] selectleak 8440 set_bits: me 0x49AF58, testing fd 0 ()
> 62 60475 [main] selectleak 8440 set_bits: ready 1
> 74 60549 [main] selectleak 8440 select_stuff::poll: returning 1
> 61 60610 [main] selectleak 8440 select_stuff::cleanup: calling cleanup
> routines
> 65 60675 [main] selectleak 8440 select_stuff::~select_stuff: deleting
> select records
> 60 60735 [main] selectleak 8440 free: (0x49AF58), called by 0x610BC2A2
> 108 60843 [main] selectleak 8440 calloc: (1, 44) = 49AF58, called by
> 61002389
> 64 60907 [main] selectleak 8440 calloc: (1, 12) = 49B018, called by
> 61002389
> 126 61033 [main] selectleak 8440 peek_pipe: , ready for read: avail 130892
> 62 61095 [main] selectleak 8440 fhandler_base::ready_for_read:
> read_ready 1, avail 1
> 62 61157 [main] selectleak 8440 select_stuff::cleanup: calling cleanup
> routines
> 61 61218 [main] selectleak 8440 select_stuff::cleanup: calling cleanup
> routines
> 62 61280 [main] selectleak 8440 select_stuff::~select_stuff: deleting
> select records
> 61 61341 [main] selectleak 8440 free: (0x49AF58), called by 0x610BC2A2
> 226 61567 [main] selectleak 8440 cygwin_select: 1, 0x23CCFC, 0x0, 0x0, 0x0
>
> Notice how the "calloc: (1, 12) = 49B018" is only freed once between the two
> "cygwin_select: 1, 0x23CCFC, ..."-lines.
>
> $ cygcheck -c cygwin gcc4
> Cygwin Package Information
> Package Version Status
> cygwin 1.7.9-1 OK
> gcc4 4.3.4-4 OK
>
> Cheers,
> Peter
Arrrg, this is the program I actually used to generate that
strace (but the leak is present in both versions). Oh well,
sorry about that...
----------------8<---(selectleak.c)---------
#include <sys/time.h>
#include <fcntl.h>
int
main(void)
{
fd_set fdset;
long flags = fcntl(0, F_GETFL);
fcntl(0, F_SETFL, flags | O_NONBLOCK);
for (;;) {
int res;
char buf[20];
FD_ZERO(&fdset);
FD_SET(0, &fdset);
res = select(1, &fdset, NULL, NULL, NULL);
if (!res)
continue;
if (res < 0)
return 1;
res = read(0, buf, sizeof(buf));
if (!res)
break;
if (res < 0)
return 1;
}
return 0;
}
----------------8<--------------------------
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