maybe the discard_buf should also be consistent with struct 
pdo_odbc_errinfo.last_err_msg 

which is "char last_err_msg[SQL_MAX_MESSAGE_LENGTH];"

diff is:

diff --git a/ext/pdo_odbc/odbc_driver.c b/ext/pdo_odbc/odbc_driver.c
index 84a147b..2176051 100755
--- a/ext/pdo_odbc/odbc_driver.c
+++ b/ext/pdo_odbc/odbc_driver.c
@@ -114,8 +114,8 @@ void pdo_odbc_error(pdo_dbh_t *dbh, pdo_stmt_t *stmt, 
PDO_ODBC_HSTMT statement,
 	 * diagnostic records (which can be generated by PRINT statements
 	 * in the query, for instance). */
 	while (rc == SQL_SUCCESS || rc == SQL_SUCCESS_WITH_INFO) {
-		char discard_state[5];
-		char discard_buf[1024];
+		char discard_state[6];
+		char discard_buf[SQL_MAX_MESSAGE_LENGTH];
 		SQLINTEGER code;
 		rc = SQLGetDiagRec(htype, eh, recno++, discard_state, &code,
 				discard_buf, sizeof(discard_buf)-1, 
&errmsgsize);

@laruence, I agree, but is this case should rather be SQL_MAX_MESSAGE_LENGTH+1 as used in unixODBC source code.

But this have no risk as this is (mostly) protected by the buffer_length arg.

From extract_sql_error_rec function source code
(unixODBC-2.3.1/DriverManager/SQLGetDiagRec.c)

    if ( sqlstate )
        strcpy((char*) sqlstate, "00000" );

Here is the buffer overflow issue (no length protection).

yeah, I think you can commit that patch. thanks

@laruence: thanks, but I don't have commit right on php-src (only on pecl)