1 files changed, 74 insertions, 9 deletions
diff --git a/src/pkg/database/sql/convert.go b/src/pkg/database/sql/convert.go
index bfcb03ccf..853a7826c 100644
--- a/src/pkg/database/sql/convert.go
+++ b/src/pkg/database/sql/convert.go
@@ -14,53 +14,115 @@ import (
 	"strconv"
 )
 
-// subsetTypeArgs takes a slice of arguments from callers of the sql
-// package and converts them into a slice of the driver package's
-// "subset types".
-func subsetTypeArgs(args []interface{}) ([]driver.Value, error) {
-	out := make([]driver.Value, len(args))
+var errNilPtr = errors.New("destination pointer is nil") // embedded in descriptive error
+
+// driverArgs converts arguments from callers of Stmt.Exec and
+// Stmt.Query into driver Values.
+//
+// The statement si may be nil, if no statement is available.
+func driverArgs(si driver.Stmt, args []interface{}) ([]driver.Value, error) {
+	dargs := make([]driver.Value, len(args))
+	cc, ok := si.(driver.ColumnConverter)
+
+	// Normal path, for a driver.Stmt that is not a ColumnConverter.
+	if !ok {
+		for n, arg := range args {
+			var err error
+			dargs[n], err = driver.DefaultParameterConverter.ConvertValue(arg)
+			if err != nil {
+				return nil, fmt.Errorf("sql: converting Exec argument #%d's type: %v", n, err)
+			}
+		}
+		return dargs, nil
+	}
+
+	// Let the Stmt convert its own arguments.
 	for n, arg := range args {
+		// First, see if the value itself knows how to convert
+		// itself to a driver type.  For example, a NullString
+		// struct changing into a string or nil.
+		if svi, ok := arg.(driver.Valuer); ok {
+			sv, err := svi.Value()
+			if err != nil {
+				return nil, fmt.Errorf("sql: argument index %d from Value: %v", n, err)
+			}
+			if !driver.IsValue(sv) {
+				return nil, fmt.Errorf("sql: argument index %d: non-subset type %T returned from Value", n, sv)
+			}
+			arg = sv
+		}
+
+		// Second, ask the column to sanity check itself. For
+		// example, drivers might use this to make sure that
+		// an int64 values being inserted into a 16-bit
+		// integer field is in range (before getting
+		// truncated), or that a nil can't go into a NOT NULL
+		// column before going across the network to get the
+		// same error.
 		var err error
-		out[n], err = driver.DefaultParameterConverter.ConvertValue(arg)
+		dargs[n], err = cc.ColumnConverter(n).ConvertValue(arg)
 		if err != nil {
-			return nil, fmt.Errorf("sql: converting argument #%d's type: %v", n+1, err)
+			return nil, fmt.Errorf("sql: converting argument #%d's type: %v", n, err)
+		}
+		if !driver.IsValue(dargs[n]) {
+			return nil, fmt.Errorf("sql: driver ColumnConverter error converted %T to unsupported type %T",
+				arg, dargs[n])
 		}
 	}
-	return out, nil
+
+	return dargs, nil
 }
 
 // convertAssign copies to dest the value in src, converting it if possible.
 // An error is returned if the copy would result in loss of information.
 // dest should be a pointer type.
 func convertAssign(dest, src interface{}) error {
-	// Common cases, without reflect.  Fall through.
+	// Common cases, without reflect.
 	switch s := src.(type) {
 	case string:
 		switch d := dest.(type) {
 		case *string:
+			if d == nil {
+				return errNilPtr
+			}
 			*d = s
 			return nil
 		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
 			*d = []byte(s)
 			return nil
 		}
 	case []byte:
 		switch d := dest.(type) {
 		case *string:
+			if d == nil {
+				return errNilPtr
+			}
 			*d = string(s)
 			return nil
 		case *interface{}:
+			if d == nil {
+				return errNilPtr
+			}
 			bcopy := make([]byte, len(s))
 			copy(bcopy, s)
 			*d = bcopy
 			return nil
 		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
 			*d = s
 			return nil
 		}
 	case nil:
 		switch d := dest.(type) {
 		case *[]byte:
+			if d == nil {
+				return errNilPtr
+			}
 			*d = nil
 			return nil
 		}
@@ -98,6 +160,9 @@ func convertAssign(dest, src interface{}) error {
 	if dpv.Kind() != reflect.Ptr {
 		return errors.New("destination not a pointer")
 	}
+	if dpv.IsNil() {
+		return errNilPtr
+	}
 
 	if !sv.IsValid() {
 		sv = reflect.ValueOf(src)