The MySQL (nonstandard extension) integer-type display width may result in allocating a buffer too small to handle integer column values that exist in rows.  Therefore, rather than rely on the MYSQL_FIELD length member (which describes display width), use MAX_BIGINT_WIDTH for all integer columns.  This approach ensures that we don't cause invalid data truncation, and does not introduce the efficiency problems that would be caused by the client-side data buffering that results from the use of max_length (which is only available when specifying the STMT_ATTR_UPDATE_MAX_LENGTH option with mysql_stmt_attr_set() followed by a call to mysql_stmt_store_result() ).

The attached patch adds a function, qIsInteger() (similar to qIsBlob() ), and sets the value of fieldInfo->length to MAX_BIGINT_WIDTH for integer columns ( http://dev.mysql.com/doc/refman/5.0/en/c-api-prepared-statement-datatypes.html ).  I felt the code complexity for handling each integer type separately was not warranted for the small amount of space savings involved (MAX_BIGINT_WIDTH is 20, MAX_INT_WIDTH is 10, MAX_MEDIUMINT_WIDTH is 8, MAX_SMALLINT_WIDTH is 5, and MAX_TINYINT_WIDTH is 3 --and all but MAX_BIGINT_WIDTH and MAX_MEDIUMINT_WIDTH require the + 1 (already done in the existing code) for the sign, unless unsigned).

MAX_BIGINT_WIDTH was added to MySQL 4.1.5 in response to MySQL bug #4788 ( http://bugs.mysql.com/bug.php?id=4788 and http://dev.mysql.com/doc/refman/4.1/en/news-4-1-5.html ), but MAX_BIGINT_WIDTH and all the other code added by this patch are only used in a section of code already protected by "#if MYSQL_VERSION_ID >= 40108" (since prepared statements are only used for MySQL 4.1.8 and above).

MAX_BIGINT_WIDTH is defined in mysql_com.h, which is included by mysql.h, which is included by qsql_mysql.h.

---

Index: qt-x11-opensource-src-4.5.3/src/sql/drivers/mysql/qsql_mysql.cpp
===================================================================
--- qt-x11-opensource-src-4.5.3.orig/src/sql/drivers/mysql/qsql_mysql.cpp	2009-12-03 01:21:13.000000000 -0500
+++ qt-x11-opensource-src-4.5.3/src/sql/drivers/mysql/qsql_mysql.cpp	2009-12-03 03:19:03.000000000 -0500
@@ -315,6 +315,15 @@
            || t == MYSQL_TYPE_LONG_BLOB;
 }
 
+static bool qIsInteger(int t)
+{
+    return t == MYSQL_TYPE_TINY
+           || t == MYSQL_TYPE_SHORT
+           || t == MYSQL_TYPE_LONG
+           || t == MYSQL_TYPE_LONGLONG
+           || t == MYSQL_TYPE_INT24;
+}
+
 void QMYSQLResultPrivate::bindBlobs()
 {
     int i;
@@ -362,6 +371,13 @@
             fieldInfo->length = 0;
             hasBlobs = true;
         } else {
+            // fieldInfo->length specifies the display width, which may be too
+            // small to hold valid integer values (see
+            // http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html ), so
+            // always use the MAX_BIGINT_WIDTH for integer types
+            if (qIsInteger(fieldInfo->type)) {
+                fieldInfo->length = MAX_BIGINT_WIDTH;
+            }
             fieldInfo->type = MYSQL_TYPE_STRING;
         }
         bind = &inBinds[i];