Re: swscanf() causing Memory Fault

[christos%astron.com@localhost (Christos Zoulas)]

In article <20081116012924.GC19936%red.tifa.renegado@localhost>,
Silas Silva  <silasdb%gmail.com@localhost> wrote:
>Hello all.
>
>I imagine this is the right list where I can send questions like that...
>here we go:
>
>Today, I compiled STFL (http://www.clifford.at/stfl/) by hand (it is not
>available in pkgsrc yet). It has a example program. When trying to run
>it, I got a Memory Fault. I got the following backtrace:
>
>    (gdb) bt
>    #0  0xbbb0b1cb in __fgetwc_unlock () from /usr/lib/libc.so.12
>    #1  0xbbb05fb1 in __vfwscanf_unlocked () from /usr/lib/libc.so.12
>    #2  0xbbb05c10 in vswscanf () from /usr/lib/libc.so.12
>    #3  0xbbad67a9 in swscanf () from /usr/lib/libc.so.12
>    #4  0x0804ac10 in stfl_widget_getkv_int (w=0x8062580, key=0x8053f20,
>defval=1) at base.c:227
>    #5  0x080500bf in wt_table_prepare (w=0x8062480, f=0x805c040) at
>widgets/wt_table.c:107
>    #6  0x0804e52a in wt_box_prepare (w=0x8062000, f=0x805c040) at
>widgets/wt_box.c:61
>    #7  0x0804b3c5 in stfl_form_run (f=0x805c040, timeout=0) at base.c:494
>    #8  0x0804986c in stfl_run (f=0x805c040, timeout=0) at public.c:55
>    #9  0x080496ec in main () at example.c:46
>    (gdb)
>
>Problem with swscanf()? The code there (base.c) looks ok... So I decided
>to try with a simple program myself. The program is:
>
>    #include <stdio.h>
>    #include <wchar.h>
>
>    int
>    main(int argc, char *argv[])
>    {
>            int ret;
>            int num;
>            wchar_t *wstr = L"5";
>            wchar_t *wfmt = L"%d";
>
>            ret = swscanf(wstr, wfmt, &num);
>
>            printf("ret: %d\n", ret);
>
>            return ret;
>    }
>
>So I compiled, ran and debugged it:
>
>    $ cc -o test test.c
>    $ ./test
>    Memory fault (core dumped)
>    $ gdb -c test.core test
>    ...
>    Program terminated with signal 11, Segmentation fault.
>    #0  0xbbb671cb in __fgetwc_unlock () from /usr/lib/libc.so.12
>    (gdb) bt
>    #0  0xbbb671cb in __fgetwc_unlock () from /usr/lib/libc.so.12
>    #1  0xbbb61fb1 in __vfwscanf_unlocked () from /usr/lib/libc.so.12
>    #2  0xbbb61c10 in vswscanf () from /usr/lib/libc.so.12
>    #3  0xbbb327a9 in swscanf () from /usr/lib/libc.so.12
>    #4  0x0804873d in main ()
>    (gdb) quit
>
>The same error...
>
>I'm not a C expert (well, I'm not event a C programmer!), but I couldn't
>find any error in the above program. I tried with other examples from
>internet, and I got the same error.
>
>Looking for a solution, I found in pkgsrc-users list that people have
>had a similar problem when trying to build Amaya 10:
>
>http://mail-index.netbsd.org/pkgsrc-users/2008/09/13/msg008031.html
>
>Any idea? Could it be a lower-level problem? The backtrace says
>something about __fgetwc_unlock().
>
>NetBSD 4.0 here. Same error in port-xen and port-i386.
>
>Thank you very much!

Index: vswscanf.c
===================================================================
RCS file: /cvsroot/src/lib/libc/stdio/vswscanf.c,v
retrieving revision 1.3
diff -u -u -r1.3 vswscanf.c
--- vswscanf.c  2 Dec 2005 13:51:22 -0000       1.3
+++ vswscanf.c  16 Nov 2008 03:14:53 -0000
@@ -90,6 +90,7 @@
                return (EOF);
        }
        _FILEEXT_SETUP(&f, &fext);
+       (void)memset(WCIO_GET(&f), 0, sizeof(struct wchar_io_data));
        f._file = -1;
        f._flags = __SRD;
        f._bf._base = f._p = (unsigned char *)mbstr;

christos