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  • From: "Lowden, James K" <LowdenJK AT bernstein.com>
  • To: "FreeTDS Development Group" <freetds AT lists.ibiblio.org>
  • Subject: RE: [freetds] Problems with large image transfers.
  • Date: Tue, 21 Sep 2004 11:22:23 -0400

-----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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