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  • From: David Lambert <dlambert AT lambsys.com>
  • To: FreeTDS Development Group <freetds AT lists.ibiblio.org>
  • Subject: Re: [freetds] Problems with large image transfers.
  • Date: Tue, 21 Sep 2004 10:56:23 -0500

Thanks for the hints. I will concentrate on the segv problem for now:

This is a test database, so please feel free to access for testing.

/usr/local/etc/freetds.conf entry:

[TRAX]
host = AHQ1003.activehost.com
port = 1433
tds version = 8.0

As requested, here is the backtrace:

Program received signal SIGSEGV, Segmentation fault.
0x00c189e2 in fwrite () from /lib/tls/libc.so.6
(gdb) backtrace
#0 0x00c189e2 in fwrite () from /lib/tls/libc.so.6
#1 0x08054d47 in _bcp_exec_out (dbproc=0x8f7a218, rows_copied=0xfef2c784)
at bcp.c:785
#2 0x08056732 in bcp_exec (dbproc=0x8f7a218, rows_copied=0xfef2c784)
at bcp.c:1624
#3 0x0804ab92 in file_character (pdata=0xfef2c7b0, dbproc=0x8f7a218, dir=2)
at freebcp.c:592
#4 0x0804982e in main (argc=13, argv=0xfef2f8e4) at freebcp.c:93


Run command was:

(gdb) run door_snaps out testbcpout -c -e errors -S TRAX -U etraxsales_user -P RxF39pqm

Lowden, James K wrote:

-----Original Message-----
From: David Lambert
Sent: Monday, September 20, 2004 10:48 PM

I am having problems using freebcp when transferring large images. If I use character format the program exits with a segmentation fault. Using the following format statement, I get:

Msg 20049, Level 4
Data-conversion resulted in overflow.

The format file is:

6.0
1
1 SYBIMAGE 0 100000 "\t" 5 snap_data

Using gdb on freebcp. The dbconvert routine is entered as follows:

dbconvert (dbproc=0x9c881e8, srctype=34, src=0x9cbe698 "ÿØÿà", srclen=4096,
desttype=34, dest=0x9caa998 "", destlen=255) at dblib.c:1673

This seems to indicate that the program thinks that the destination length (255?) is shorter than the source length (4096).
-----END-----

Can you really use tab-delimited image data? The image is guaranteed never to include 0x9?
Assuming that's OK, the only way I can see that the destlen would be 255 is if the
server says so. If the file data are longer than 4096, there's a "special
hack" in _bcp_read_hostfile that sets the destlen to the larger size. Else the
server's column size is used. Since you're looking at things with gdb already, trace
through _bcp_read_hostfile to see for yourself. ;-)

Things to double check:

1. The CREATE statement for the table. 2. The TDS protocol version. 3. The version of FreeTDS.
Note that dbconvert() is converting type 34 to 34 i.e., no conversion. The "Data-conversion resulted in overflow" message comes straight from dbconvert() when it can't copy the source to the destination because the destlen is too small.
BTW, freebcp should *never* segfault, so you found a bug. A backtrace would be very helpful.
There's more we can do, but let's get our ducks in a row first and see where we are.
Regards,
--jkl

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