fix(extgen): use RETURN_EMPTY_STRING() when returning empty string (#2049)

One last bug spotted by #1984, empty strings should be returned using
`RETURN_EMPTY_STRING()` or it may segfault.

Author: alexandre-daubois

internal/extgen/cfile_phpmethod_test.go

@@ -185,3 +185,32 @@ func TestCFile_PHP_METHOD_Integration(t *testing.T) {
 		require.NotContains(t, fullContent, old, "Did not expect to find old declaration %q in full C file content", old)
 	}
 }
+
+func TestCFile_ClassMethodStringReturn(t *testing.T) {
+	generator := &Generator{
+		BaseName: "test_extension",
+		Classes: []phpClass{
+			{
+				Name:     "TestClass",
+				GoStruct: "TestClass",
+				Methods: []phpClassMethod{
+					{
+						Name:       "getString",
+						PhpName:    "getString",
+						ReturnType: "string",
+						ClassName:  "TestClass",
+					},
+				},
+			},
+		},
+		BuildDir: t.TempDir(),
+	}
+
+	cFileGen := cFileGenerator{generator: generator}
+	content, err := cFileGen.getTemplateContent()
+	require.NoError(t, err)
+
+	require.Contains(t, content, "if (result)", "Expected NULL check for string return")
+	require.Contains(t, content, "RETURN_STR(result)", "Expected RETURN_STR macro")
+	require.Contains(t, content, "RETURN_EMPTY_STRING()", "Expected RETURN_EMPTY_STRING fallback")
+}

internal/extgen/templates/extension.c.tpl

@@ -114,7 +114,10 @@ PHP_METHOD({{namespacedClassName $.Namespace .ClassName}}, {{.PhpName}}) {
     {{- if ne .ReturnType "void"}}
     {{- if eq .ReturnType "string"}}
     zend_string* result = {{.Name}}_wrapper(intern->go_handle{{if .Params}}{{range .Params}}, {{if .IsNullable}}{{if eq .PhpType "string"}}{{.Name}}_is_null ? NULL : {{.Name}}{{else if eq .PhpType "int"}}{{.Name}}_is_null ? NULL : &{{.Name}}{{else if eq .PhpType "float"}}{{.Name}}_is_null ? NULL : &{{.Name}}{{else if eq .PhpType "bool"}}{{.Name}}_is_null ? NULL : &{{.Name}}{{else if eq .PhpType "array"}}{{.Name}}{{end}}{{else}}{{.Name}}{{end}}{{end}}{{end}});
-    RETURN_STR(result);
+    if (result) {
+        RETURN_STR(result);
+    }
+    RETURN_EMPTY_STRING();
     {{- else if eq .ReturnType "int"}}
     zend_long result = {{.Name}}_wrapper(intern->go_handle{{if .Params}}{{range .Params}}, {{if .IsNullable}}{{if eq .PhpType "string"}}{{.Name}}_is_null ? NULL : {{.Name}}{{else if eq .PhpType "int"}}{{.Name}}_is_null ? NULL : &{{.Name}}{{else if eq .PhpType "float"}}{{.Name}}_is_null ? NULL : &{{.Name}}{{else if eq .PhpType "bool"}}{{.Name}}_is_null ? NULL : &{{.Name}}{{else if eq .PhpType "array"}}{{.Name}}{{end}}{{else}}{{if eq .PhpType "array"}}{{.Name}}{{else}}(long){{.Name}}{{end}}{{end}}{{end}}{{end}});
     RETURN_LONG(result);