ODBC failure on basic call

[oneeyeman1]

Hi,

I have following code:

for( int i = 0; i < 5; i++ )
{
catalog[i].TargetType = SQL_C_WCHAR;
catalog[i].BufferLength = ( bufferSize + 1 );
catalog[i].TargetValuePtr = malloc( sizeof( unsigned char ) * catalog[i].BufferLength );
ret = SQLBindCol( m_hstmt, (SQLUSMALLINT) i + 1, catalog[i].TargetType, catalog[i].TargetValuePtr, catalog[i].BufferLength, &( catalog[i].StrLen_or_Ind ) );
if( ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO )
{
GetErrorMessage( errorMsg, STMT_ERROR );
result = 1;
break;
}
}

This code fails with HY090.

However it didn't fail with any other DBMS.

Im running SQL Anywhere 17.0 with the driver 17.0.

Any idea?

Thank you.

[chris_keating]

I don't see anything specific in this code snippet nor can I reproduce the error in an more complete implementation. I would suggest getting an ODBC trace. In that trace, please ensure that the SQL_ATTR_ODBC_VERSION is set to SQL_OV_ODBC3 (SQLSetEnvAttr)  and then look for the 

DIAG [HY090] [Microsoft][ODBC Driver Manager] Invalid string or buffer length (0)

to confirm what ODBC function encounters the error. A call to SQLBindCol has a context for the error related to the BufferLength being not negative.  If it is coming from a different ODBC function, share what that function is and how your application has implemented it.

This really does not appear to be a SQLA driver issue. If you can share the trace, we can use ODBCTest to replay the ODBC calls leading to the error.   

[oneeyeman1]

@chris_keating, I generated the log file. Please do let me know how and where to upload/send it. This site interface is not designed to do that. Thx.

[oneeyeman1]

The code Im trying comes straight from https://learn.microsoft.com/en-us/sql/odbc/reference/syntax/sqltables-function?view=sql-server-ver17.....

[chris_keating]

I spoke with a SQL Anywhere ODBC driver developer to confirm what is happening.  The buffer is measured in bytes and SQL Anywhere expects the buffer to be an even value when processing wide characters i.e., SQL_C_WCHAR, and sized sufficiently for the value being accessed.  In the SQLTables example, it is using SQL_C_CHAR so is not impacted by this.  So, use an even value when you are setting the catalog[i].BufferLength with SQL_C_WCHAR.

[oneeyeman1]

@chris_keating, So what should be done? My app is unicode one and so it should work with SQL_W_CHAR... Also as mentioned - SQL Server, PostgreSQL, MySQL and probably SAP ASE (from memory) works correctly. Does using +1 fixes it?

[jack_schueler]

Re: Will try to submit to MS. Are you suggesting that Microsoft posted the sample code that you provided? Where did you find it? I am surprised that MS would provide an example that has an odd-length buffer size.

[oneeyeman1]

@Jack_shueler, take a look at https://learn.microsoft.com/en-us/sql/odbc/reference/syntax/sqltables-function?view=sql-server-ver17...

[jack_schueler]

The referenced web page has a correct example. It uses a 1-byte SQL_C_CHAR (SQLCHAR type). You modified the datatype to 2-byte SQL_C_WCHAR but did not double the buffer length.

[jack_schueler · Accepted solution]

// Instead of writing this ...
catalog[i].BufferLength = ( bufferSize + 1 );
// write this ...
// Note that some ODBC drivers have a 2-byte SQLWCHAR (like us) and 
// some ODBC drivers have a 4-byte SQLWCHAR, so write this.
catalog[i].BufferLength = ( characterSize + 1 ) * sizeof(SQLWCHAR);
// Example: for CHAR(10) data, characterSize = 10 and 
// the + 1 accounts for a null terminator.
// Analogously, the following works for non-wide SQLCHAR.
catalog[i].BufferLength = ( characterSize + 1 ) * sizeof(SQLCHAR);
// To generalize the "BufferLength" value ...
characterSize = n; // Ex: 10 for SQL CHAR(10) or VARCHAR(10)
sizeofCharacter = sizeof(SQLWCHAR); //or sizeof(SQLCHAR)
catalog[i].BufferLength = ( characterSize + 1 ) * sizeofCharacter;

[oneeyeman1 · Accepted solution]

@Jack_shueler, the generalized solution works fine for SQL Anywhere on Windows. Will check ther DBMSes and OSes later. Thx.

[oneeyeman1 · Accepted solution]

@Jack_shueler, I checked and it looks like it works for SQL Server from Windows as well. However, it means that the code I referenced is wrong... Will try to submit to MS...

[oneeyeman1 · Accepted solution]

@Jack_shueler, , it works even on Linux with unixODBC. Thx for the solution.