Ensure long data column buffers are freed (#306)

The bind_type of the column stored in the StatementData object was not
copied over to the ColumnData object created for each row. This means
that the ColumnData destructor will not free the allocated buffer used
with SQLGetData.

Additionally, for SQL_C_BINARY columns, the data was never freed either
since the destructor only checked for SQL_C_CHAR and SQL_C_WCHAR.

Finally, because long data allocations are created using malloc/realloc,
we need to set a flag to use free instead of delete[] in the destructor.
On platforms we support, this shouldn't actually make any difference,
but it is mandated by the spec and reduces noise in valgrind.

Signed-off-by: Kevin Adler <[email protected]>

src/odbc.h

@@ -124,6 +124,7 @@ typedef struct Parameter {
 
 typedef struct ColumnData {
   SQLSMALLINT bind_type;
+  bool use_free;
   union {
     SQLCHAR      *char_data;
     SQLWCHAR     *wchar_data;
@@ -137,13 +138,21 @@ typedef struct ColumnData {
   SQLLEN    size;
 
   ~ColumnData() {
-    if (bind_type == SQL_C_CHAR) {
-      delete[] this->char_data;
-      return;
+    if (bind_type == SQL_C_CHAR || bind_type == SQL_C_BINARY) {
+      if (use_free) {
+        free(this->char_data);
+      }
+      else {
+        delete[] this->char_data;
+      }
     }
-    if (bind_type == SQL_C_WCHAR) {
-      delete[] this->wchar_data;
-      return;
+    else if (bind_type == SQL_C_WCHAR) {
+      if (use_free) {
+        free(this->wchar_data);
+      }
+      else {
+        delete[] this->wchar_data;
+      }
     }
   }
 

src/odbc_connection.cpp

@@ -3589,6 +3589,8 @@ fetch_and_store
           // Iterate over each column, putting the data in the row object
           for (int column_index = 0; column_index < data->column_count; column_index++)
           {
+            row[column_index].bind_type = data->columns[column_index]->bind_type;
+
             // The column contained SQL_(W)LONG* data, so we didn't call
             // SQLBindCol, and therefore there is no data to move from a buffer.
             // Instead, call SQLGetData, and adjust buffer size accordingly
@@ -3600,6 +3602,10 @@ fetch_and_store
               SQLLEN     string_length_or_indicator;
               SQLLEN     data_returned_length = 0;
 
+              // We're allocating with malloc/realloc here, so the destructor
+              // needs to use free instead of delete[].
+              row[column_index].use_free = true;
+
               if (data->columns[column_index]->bind_type == SQL_C_WCHAR)
               {
                 row[column_index].wchar_data = (SQLWCHAR *)malloc(buffer_size);