report actual error message if sqlite3_load_extension fails

_example/mod_regexp/Makefile

@@ -1,22 +1,27 @@
 ifeq ($(OS),Windows_NT)
 EXE=extension.exe
-EXT=sqlite3_mod_regexp.dll
+LIB_EXT=dll
 RM=cmd /c del
 LDFLAG=
 else
 EXE=extension
-EXT=sqlite3_mod_regexp.so
-RM=rm
+ifeq ($(shell uname -s),Darwin)
+LIB_EXT=dylib
+else
+LIB_EXT=so
+endif
+RM=rm -f
 LDFLAG=-fPIC
 endif
+LIB=sqlite3_mod_regexp.$(LIB_EXT)
 
-all : $(EXE) $(EXT)
+all : $(EXE) $(LIB)
 
 $(EXE) : extension.go
 	go build $<
 
-$(EXT) : sqlite3_mod_regexp.c
+$(LIB) : sqlite3_mod_regexp.c
 	gcc $(LDFLAG) -shared -o $@ $< -lsqlite3 -lpcre
 
 clean :
-	@-$(RM) $(EXE) $(EXT)
+	@-$(RM) $(EXE) $(LIB)

_example/mod_vtable/Makefile

@@ -1,24 +1,29 @@
 ifeq ($(OS),Windows_NT)
 EXE=extension.exe
-EXT=sqlite3_mod_vtable.dll
+LIB_EXT=dll
 RM=cmd /c del
 LIBCURL=-lcurldll
 LDFLAG=
 else
 EXE=extension
-EXT=sqlite3_mod_vtable.so
-RM=rm
+ifeq ($(shell uname -s),Darwin)
+LIB_EXT=dylib
+else
+LIB_EXT=so
+endif
+RM=rm -f
 LDFLAG=-fPIC
 LIBCURL=-lcurl
 endif
+LIB=sqlite3_mod_vtable.$(LIB_EXT)
 
-all : $(EXE) $(EXT)
+all : $(EXE) $(LIB)
 
 $(EXE) : extension.go
 	go build $<
 
-$(EXT) : sqlite3_mod_vtable.cc
+$(LIB) : sqlite3_mod_vtable.cc
 	g++ $(LDFLAG) -shared -o $@ $< -lsqlite3 $(LIBCURL)
 
 clean :
-	@-$(RM) $(EXE) $(EXT)
+	@-$(RM) $(EXE) $(LIB)

_example/mod_vtable/sqlite3_mod_vtable.cc

@@ -1,6 +1,6 @@
 #include <string>
 #include <sstream>
-#include <sqlite3-binding.h>
+#include <sqlite3.h>
 #include <sqlite3ext.h>
 #include <curl/curl.h>
 #include "picojson.h"

sqlite3_load_extension.go

@@ -28,19 +28,17 @@ func (c *SQLiteConn) loadExtensions(extensions []string) error {
 	}
 
 	for _, extension := range extensions {
-		cext := C.CString(extension)
-		defer C.free(unsafe.Pointer(cext))
-		rv = C.sqlite3_load_extension(c.db, cext, nil, nil)
-		if rv != C.SQLITE_OK {
+		if err := c.loadExtension(extension, nil); err != nil {
 			C.sqlite3_enable_load_extension(c.db, 0)
-			return errors.New(C.GoString(C.sqlite3_errmsg(c.db)))
+			return err
 		}
 	}
 
 	rv = C.sqlite3_enable_load_extension(c.db, 0)
 	if rv != C.SQLITE_OK {
 		return errors.New(C.GoString(C.sqlite3_errmsg(c.db)))
 	}
+
 	return nil
 }
 
@@ -51,19 +49,35 @@ func (c *SQLiteConn) LoadExtension(lib string, entry string) error {
 		return errors.New(C.GoString(C.sqlite3_errmsg(c.db)))
 	}
 
-	clib := C.CString(lib)
-	defer C.free(unsafe.Pointer(clib))
-	centry := C.CString(entry)
-	defer C.free(unsafe.Pointer(centry))
+	if err := c.loadExtension(lib, &entry); err != nil {
+		C.sqlite3_enable_load_extension(c.db, 0)
+		return err
+	}
 
-	rv = C.sqlite3_load_extension(c.db, clib, centry, nil)
+	rv = C.sqlite3_enable_load_extension(c.db, 0)
 	if rv != C.SQLITE_OK {
 		return errors.New(C.GoString(C.sqlite3_errmsg(c.db)))
 	}
 
-	rv = C.sqlite3_enable_load_extension(c.db, 0)
+	return nil
+}
+
+func (c *SQLiteConn) loadExtension(lib string, entry *string) error {
+	clib := C.CString(lib)
+	defer C.free(unsafe.Pointer(clib))
+
+	var centry *C.char
+	if entry != nil {
+		centry := C.CString(*entry)
+		defer C.free(unsafe.Pointer(centry))
+	}
+
+	var errMsg *C.char
+	defer C.sqlite3_free(unsafe.Pointer(errMsg))
+
+	rv := C.sqlite3_load_extension(c.db, clib, centry, &errMsg)
 	if rv != C.SQLITE_OK {
-		return errors.New(C.GoString(C.sqlite3_errmsg(c.db)))
+		return errors.New(C.GoString(errMsg))
 	}
 
 	return nil

sqlite3_load_extension_test.go

@@ -0,0 +1,63 @@
+// Copyright (C) 2019 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+// +build !sqlite_omit_load_extension
+
+package sqlite3
+
+import (
+	"database/sql"
+	"testing"
+)
+
+func TestExtensionsError(t *testing.T) {
+	sql.Register("sqlite3_TestExtensionsError",
+		&SQLiteDriver{
+			Extensions: []string{
+				"foobar",
+			},
+		},
+	)
+
+	db, err := sql.Open("sqlite3_TestExtensionsError", ":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = db.Ping()
+	if err == nil {
+		t.Fatal("expected error loading non-existent extension")
+	}
+
+	if err.Error() == "not an error" {
+		t.Fatal("expected error from sqlite3_enable_load_extension to be returned")
+	}
+}
+
+func TestLoadExtensionError(t *testing.T) {
+	sql.Register("sqlite3_TestLoadExtensionError",
+		&SQLiteDriver{
+			ConnectHook: func(c *SQLiteConn) error {
+				return c.LoadExtension("foobar", "")
+			},
+		},
+	)
+
+	db, err := sql.Open("sqlite3_TestLoadExtensionError", ":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	err = db.Ping()
+	if err == nil {
+		t.Fatal("expected error loading non-existent extension")
+	}
+
+	if err.Error() == "not an error" {
+		t.Fatal("expected error from sqlite3_enable_load_extension to be returned")
+	}
+}