diff --git a/core/ControllableTask.h b/core/ControllableTask.h
index f9ac030..70a44fa 100644
--- a/core/ControllableTask.h
+++ b/core/ControllableTask.h
@@ -5,7 +5,8 @@
  * https://stackoverflow.com/questions/5423058/qfuture-that-can-be-cancelled-and-report-progress
  */
 
-#include "TaskControl.h"
+//#include "TaskControl.h"
+class TaskControl;
 
 template <class T>
 class ControllableTask
diff --git a/core/SqlAstExpression.cpp b/core/SqlAstExpression.cpp
index 618fce3..93bbc88 100644
--- a/core/SqlAstExpression.cpp
+++ b/core/SqlAstExpression.cpp
@@ -9,5 +9,5 @@ std::shared_ptr<SqlAst::Expression> parseExpression(SqlParser &parser)
 	// number
 	// symbol
 	// left parenthesis
-
+	return nullptr;
 }
diff --git a/pglab/QueryTab.cpp b/pglab/QueryTab.cpp
index 53b2d1a..465311a 100644
--- a/pglab/QueryTab.cpp
+++ b/pglab/QueryTab.cpp
@@ -538,7 +538,7 @@ void QueryTab::markError(const Pgsql::ErrorDetails &details)
 
 		int length = 0;
 		if (details.state == "42703") {
-			int pos = details.messagePrimary.find('"');
+			std::size_t pos = details.messagePrimary.find('"');
 			if (pos != std::string::npos) {
 				int pos2 = details.messagePrimary.find('"', pos+1);
 				if (pos2 != std::string::npos) {
@@ -547,7 +547,7 @@ void QueryTab::markError(const Pgsql::ErrorDetails &details)
 			}
 		}
 		else if (details.state == "42P01") {
-			int pos = details.messagePrimary.find('"');
+			std::size_t pos = details.messagePrimary.find('"');
 			if (pos != std::string::npos) {
 				int pos2 = details.messagePrimary.find('"', pos+1);
 				if (pos2 != std::string::npos) {