PRB: SQLGetData w/ SQL_C_BINARY Causes GPF in 16-bit ODBC Test

• Microsoft Open Database Connectivity, version 2.10x

SYMPTOMS

Inside 16-bit ODBC Test, when you call SQLGetData with SQL_C_BINARY on a column holding more than 40 bytes and cbValueMax is set to be smaller than the actual size of data in the column, the following general protection fault (GPF) will be raised:

    ODBCTEST caused a General Protection Fault in
    module ODBCTEST.EXE at 0001:BF33

WORKAROUND

There are two resolutions for this problem in 16-bit ODBC Test:

1. Specify cbValueMax large enough to get data back by one SQLGetData call.

2. Replace SQL_C_BINARY with SQL_C_CHAR for fCType. The following text is an excerpt from "ODBC 2.0 Programmer's Reference Book," Appendix D. Please refer to this book for more information before you use this method:

         When binary SQL data is converted to character C data, each byte (8
         bits) of source data is represented as two ASCII characters. These
         characters are the ASCII character representation of the number in
         its hexadecimal form. For example, a binary 00000001 is converted to
         "01" and a binary 11111111 is converted to "FF".
   

         The driver always converts individual bytes to pairs of hexadecimal
         digits and terminates the character string with a null byte. Because
         of this, if cbValueMax is even and is less than the length of the
         converted data, the last byte of the rgbValue buffer is not used.
         (The converted data requires an even number of bytes, the
         next-to-last byte is a null byte, and the last byte cannot be used.)
   

MORE INFORMATION

Here are the steps to reproduce the error:

1. "Full Connect" to an ODBC data source;

2. SQLExecuteDirect:

         create table test(col1 varchar(50))
   

3. SQLExecuteDirect:

         insert into test values ('<40 characters>')
   

4. SQLExecuteDirect:

         select * from test
   

5. SQLFetch;

6. SQLGetData(hstmt, icol=1, fCType=SQL_C_BINARY, rgbValue, cbValueMax=10, pcbValue)