Bulk lazy initialization of FunctionDefinitions (#1425)

Signed-off-by: Takeshi Yoneda <t.y.mathetake@gmail.com>
Co-authored-by: Edoardo Vacchi <evacchi@users.noreply.github.com>

internal/wasm/function_definition_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/tetratelabs/wazero/api"
+	"github.com/tetratelabs/wazero/internal/testing/hammer"
 	"github.com/tetratelabs/wazero/internal/testing/require"
 )
 
@@ -253,7 +254,25 @@ func TestModule_BuildFunctionDefinitions(t *testing.T) {
 	for _, tc := range tests {
 		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
-			tc.m.BuildFunctionDefinitions()
+			tc.m.buildFunctionDefinitions()
+			require.Equal(t, tc.expected, tc.m.FunctionDefinitionSection)
+			require.Equal(t, tc.expectedImports, tc.m.ImportedFunctions())
+			require.Equal(t, tc.expectedExports, tc.m.ExportedFunctions())
+		})
+	}
+
+	// Execute the same tests with n=`concurrentCount` goroutines invoking `buildFunctionDefinitions()` at once.
+	const nGoroutines = 100
+	const nIterations = 10
+	for _, tc := range tests {
+		tc := tc
+		testName := tc.name + " (concurrent)"
+		t.Run(testName, func(t *testing.T) {
+			hammer.NewHammer(t, nGoroutines, nIterations).
+				Run(func(name string) {
+					tc.m.buildFunctionDefinitions()
+				}, nil)
+
 			require.Equal(t, tc.expected, tc.m.FunctionDefinitionSection)
 			require.Equal(t, tc.expectedImports, tc.m.ImportedFunctions())
 			require.Equal(t, tc.expectedExports, tc.m.ExportedFunctions())