zend_portability: Remove EMPTY_SWITCH_DEFAULT_CASE()

This macro is exactly as long as explicitly spelling out its definition
(excluding the useless `break;`), but hides control flow in its definition.
This is giving tools like Coccinelle some troubles to understand the code and
can also be confusing for the human reader, because it appears as if it is a
statement that belongs to the current case rather than opening a new case.

Author: TimWolla

UPGRADING.INTERNALS

@@ -20,6 +20,8 @@ PHP 8.6 INTERNALS UPGRADE NOTES
   . The misnamed ZVAL_IS_NULL() has been removed. Use Z_ISNULL() instead.
   . New zend_class_entry.ce_flags2 and zend_function.fn_flags2 fields were
     added, given the primary flags were running out of bits.
+  . The EMPTY_SWITCH_DEFAULT_CASE() macro has been removed. Use
+    `default: ZEND_UNREACHABLE();` instead.
 
 ========================
 2. Build system changes

Zend/Optimizer/sccp.c

@@ -1592,7 +1592,7 @@ static void sccp_visit_instr(scdf_ctx *scdf, zend_op *opline, zend_ssa_op *ssa_o
 				case ZEND_SHORT_CIRCUITING_CHAIN_EMPTY:
 					ZVAL_TRUE(&zv);
 					break;
-				EMPTY_SWITCH_DEFAULT_CASE()
+				default: ZEND_UNREACHABLE();
 			}
 			SET_RESULT(result, &zv);
 			break;

Zend/Optimizer/zend_inference.c

@@ -1063,7 +1063,7 @@ static bool zend_inference_calc_binary_op_range(
 		case ZEND_BW_XOR:
 			// TODO
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 	return 0;
 }
@@ -2351,7 +2351,7 @@ static uint32_t binary_op_result_type(
 			/* TODO: +MAY_BE_OBJECT ??? */
 			tmp = MAY_BE_STRING | MAY_BE_RC1 | MAY_BE_RCN;
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 	return tmp;
 }
@@ -3709,7 +3709,7 @@ static zend_always_inline zend_result _zend_update_type_info(
 							case ZEND_FREE:
 								/* This may happen if the using opcode is DCEd.  */
 								break;
-							EMPTY_SWITCH_DEFAULT_CASE()
+							default: ZEND_UNREACHABLE();
 						}
 						j = zend_ssa_next_use(ssa->ops, ssa_op->result_def, j);
 						if (j >= 0) {
@@ -5296,10 +5296,10 @@ ZEND_API bool zend_may_throw_ex(const zend_op *opline, const zend_ssa_op *ssa_op
 					return (t1 & MAY_BE_OBJECT);
 				case IS_OBJECT:
 					return 0;
-				EMPTY_SWITCH_DEFAULT_CASE()
+				default: ZEND_UNREACHABLE();
 			}
 			/* GCC is getting confused here for the Wimplicit-fallthrough warning with
-			 * EMPTY_SWITCH_DEFAULT_CASE() macro */
+			 * default: ZEND_UNREACHABLE(); macro */
 			return 0;
 		case ZEND_ARRAY_KEY_EXISTS:
 			if ((t2 & MAY_BE_ANY) != MAY_BE_ARRAY) {

Zend/zend_API.c

@@ -147,7 +147,7 @@ ZEND_API const char *zend_get_type_by_const(int type) /* {{{ */
 			return "mixed";
 		case _IS_NUMBER:
 			return "int|float";
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */
@@ -283,7 +283,7 @@ ZEND_API ZEND_COLD void ZEND_FASTCALL zend_wrong_parameter_error(int error_code,
 		case ZPP_ERROR_FAILURE:
 			ZEND_ASSERT(EG(exception) && "Should have produced an error already");
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */

Zend/zend_ast.c

@@ -731,7 +731,7 @@ static zend_result ZEND_FASTCALL zend_ast_evaluate_inner(
 					case IS_OBJECT:
 						zend_cast_zval_to_object(result, &op1, IS_VAR);
 						break;
-					EMPTY_SWITCH_DEFAULT_CASE();
+					default: ZEND_UNREACHABLE();
 				}
 				zval_ptr_dtor_nogc(&op1);
 				if (UNEXPECTED(EG(exception))) {
@@ -1852,7 +1852,7 @@ static ZEND_COLD void zend_ast_export_zval(smart_str *str, const zval *zv, int p
 		case IS_CONSTANT_AST:
 			zend_ast_export_ex(str, Z_ASTVAL_P(zv), priority, indent);
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 }
 
@@ -2287,7 +2287,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				case T_PROPERTY_C: APPEND_STR("__PROPERTY__");
 				case T_NS_C:     APPEND_STR("__NAMESPACE__");
 				case T_CLASS_C:  APPEND_STR("__CLASS__");
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
 		case ZEND_AST_TYPE:
@@ -2296,7 +2296,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				case IS_CALLABLE: APPEND_STR("callable");
 				case IS_STATIC:   APPEND_STR("static");
 				case IS_MIXED:    APPEND_STR("mixed");
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
 
@@ -2323,7 +2323,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				case IS_STRING:    PREFIX_OP("(string)", 240, 241);
 				case IS_ARRAY:     PREFIX_OP("(array)",  240, 241);
 				case IS_OBJECT:    PREFIX_OP("(object)", 240, 241);
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
 		case ZEND_AST_CAST_VOID:
@@ -2357,14 +2357,14 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				case ZEND_REQUIRE_ONCE: FUNC_OP("require_once");
 				case ZEND_REQUIRE:      FUNC_OP("require");
 				case ZEND_EVAL:         FUNC_OP("eval");
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
 		case ZEND_AST_UNARY_OP:
 			switch (ast->attr) {
 				case ZEND_BW_NOT:   PREFIX_OP("~", 240, 241);
 				case ZEND_BOOL_NOT: PREFIX_OP("!", 240, 241);
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
 		case ZEND_AST_PRE_INC:
@@ -2463,7 +2463,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 					case ZEND_FETCH_CLASS_PARENT:
 						smart_str_append(str, ZSTR_KNOWN(ZEND_STR_PARENT));
 						break;
-					EMPTY_SWITCH_DEFAULT_CASE()
+					default: ZEND_UNREACHABLE();
 				}
 			} else {
 				zend_ast_export_ns_name(str, ast->child[0], 0, indent);
@@ -2486,7 +2486,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				case ZEND_BW_AND: BINARY_OP(" &= ",  90, 91, 90);
 				case ZEND_BW_XOR: BINARY_OP(" ^= ",  90, 91, 90);
 				case ZEND_POW:    BINARY_OP(" **= ", 90, 91, 90);
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
 		case ZEND_AST_ASSIGN_COALESCE: BINARY_OP(" \?\?= ", 90, 91, 90);
@@ -2512,7 +2512,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 				case ZEND_POW:                 BINARY_OP(" ** ",  250, 251, 250);
 				case ZEND_BOOL_XOR:            BINARY_OP(" xor ",  40,  40,  41);
 				case ZEND_SPACESHIP:           BINARY_OP(" <=> ", 180, 181, 181);
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
 		case ZEND_AST_GREATER:                 BINARY_OP(" > ",   180, 181, 181);
@@ -2864,7 +2864,7 @@ static ZEND_COLD void zend_ast_export_ex(smart_str *str, zend_ast *ast, int prio
 			zend_ast_export_indent(str, indent);
 			smart_str_appendc(str, '}');
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 	return;
 
@@ -2961,7 +2961,7 @@ zend_ast * ZEND_FASTCALL zend_ast_with_attributes(zend_ast *ast, zend_ast *attr)
 		 * zend_compile_const_decl() checks the kind of the list elements. */
 		ast = zend_ast_list_add(ast, attr);
 		break;
-	EMPTY_SWITCH_DEFAULT_CASE()
+	default: ZEND_UNREACHABLE();
 	}
 
 	return ast;

Zend/zend_compile.c

@@ -872,7 +872,7 @@ static const char *zend_modifier_token_to_string(uint32_t token)
 			return "protected(set)";
 		case T_PRIVATE_SET:
 			return "private(set)";
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 
@@ -1818,7 +1818,7 @@ static bool zend_try_compile_const_expr_resolve_class_name(zval *zv, zend_ast *c
 		case ZEND_FETCH_CLASS_DEFAULT:
 			ZVAL_STR(zv, zend_resolve_class_name_ast(class_ast));
 			return 1;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */
@@ -2262,7 +2262,7 @@ static void zend_adjust_for_fetch_type(zend_op *opline, znode *result, uint32_t
 		case BP_VAR_UNSET:
 			opline->opcode += 5 * factor;
 			return;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */
@@ -2425,7 +2425,7 @@ static inline void zend_update_jump_target(uint32_t opnum_jump, uint32_t opnum_t
 		case ZEND_JMP_FRAMELESS:
 			opline->op2.opline_num = opnum_target;
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */
@@ -3539,7 +3539,7 @@ static void zend_compile_assign(znode *result, zend_ast *ast) /* {{{ */
 
 			zend_compile_list_assign(result, var_ast, &expr_node, var_ast->attr);
 			return;
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */
@@ -3683,7 +3683,7 @@ static void zend_compile_compound_assign(znode *result, zend_ast *ast) /* {{{ */
 			opline = zend_emit_op_data(&expr_node);
 			opline->extended_value = cache_slot;
 			return;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */
@@ -4925,7 +4925,7 @@ static zend_result zend_compile_func_sprintf(znode *result, zend_ast_list *args)
 				case 'd':
 					zend_emit_op_tmp(&elements[placeholder_count], ZEND_CAST, &elements[placeholder_count], NULL)->extended_value = IS_LONG;
 					break;
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 
 			if (rope_elements == 0) {
@@ -5077,7 +5077,7 @@ static const char *zend_get_cstring_from_property_hook_kind(zend_property_hook_k
 			return "get";
 		case ZEND_PROPERTY_HOOK_SET:
 			return "set";
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 
@@ -5597,7 +5597,7 @@ static void zend_compile_unset(zend_ast *ast) /* {{{ */
 			opline = zend_compile_static_prop(NULL, var_ast, BP_VAR_UNSET, false, false);
 			opline->opcode = ZEND_UNSET_STATIC_PROP;
 			return;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 /* }}} */
@@ -9168,7 +9168,7 @@ static void zend_compile_use_trait(zend_ast *ast) /* {{{ */
 			case ZEND_AST_TRAIT_ALIAS:
 				zend_compile_trait_alias(adaptation_ast);
 				break;
-			EMPTY_SWITCH_DEFAULT_CASE()
+			default: ZEND_UNREACHABLE();
 		}
 	}
 }
@@ -9543,7 +9543,7 @@ static HashTable *zend_get_import_ht(uint32_t type) /* {{{ */
 				zend_hash_init(FC(imports_const), 8, NULL, str_dtor, 0);
 			}
 			return FC(imports_const);
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 
 	return NULL;
@@ -9559,7 +9559,7 @@ static char *zend_get_use_type_str(uint32_t type) /* {{{ */
 			return " function";
 		case ZEND_SYMBOL_CONST:
 			return " const";
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 
 	return " unknown";
@@ -9926,7 +9926,7 @@ static bool zend_try_ct_eval_magic_const(zval *zv, zend_ast *ast) /* {{{ */
 				ZVAL_EMPTY_STRING(zv);
 			}
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 
 	return 1;
@@ -10670,7 +10670,7 @@ static void zend_compile_assign_coalesce(znode *result, zend_ast *ast) /* {{{ */
 			zend_emit_op_data(&default_node);
 			assign_node = var_node_w;
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 
 	opline = zend_emit_op_tmp(NULL, ZEND_QM_ASSIGN, &assign_node, NULL);
@@ -10890,7 +10890,7 @@ static void zend_compile_isset_or_empty(znode *result, zend_ast *ast) /* {{{ */
 			opline = zend_compile_static_prop(result, var_ast, BP_VAR_IS, false, false);
 			opline->opcode = ZEND_ISSET_ISEMPTY_STATIC_PROP;
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 
 	result->op_type = opline->result_type = IS_TMP_VAR;
@@ -11407,7 +11407,7 @@ static void zend_compile_const_expr_class_name(zend_ast **ast_ptr) /* {{{ */
 			zend_error_noreturn(E_COMPILE_ERROR,
 				"static::class cannot be used for compile-time class name resolution");
 			return;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 
@@ -11510,7 +11510,7 @@ static void zend_compile_const_expr_fcc(zend_ast **ast_ptr)
 		case ZEND_AST_STATIC_CALL:
 			args_ast = &(*ast_ptr)->child[2];
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 	if ((*args_ast)->kind != ZEND_AST_CALLABLE_CONVERT) {
 		zend_error_noreturn(E_COMPILE_ERROR, "Constant expression contains invalid operations");
@@ -11548,7 +11548,7 @@ static void zend_compile_const_expr_fcc(zend_ast **ast_ptr)
 			}
 			break;
 		}
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 }
 

Zend/zend_compile.h

@@ -430,7 +430,7 @@ static zend_always_inline uint32_t zend_visibility_to_set_visibility(uint32_t vi
 			return ZEND_ACC_PROTECTED_SET;
 		case ZEND_ACC_PRIVATE:
 			return ZEND_ACC_PRIVATE_SET;
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 }
 

Zend/zend_execute.c

@@ -1790,10 +1790,10 @@ ZEND_API ZEND_COLD void zend_wrong_string_offset_error(void)
 				case ZEND_FETCH_DIM_INCDEC:
 					msg = "Cannot increment/decrement string offsets";
 					break;
-				EMPTY_SWITCH_DEFAULT_CASE();
+				default: ZEND_UNREACHABLE();
 			}
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE();
+		default: ZEND_UNREACHABLE();
 	}
 	ZEND_ASSERT(msg != NULL);
 	zend_throw_error(NULL, "%s", msg);
@@ -3502,7 +3502,7 @@ static zend_never_inline bool zend_handle_fetch_obj_flags(
 				ZEND_REF_ADD_TYPE_SOURCE(Z_REF_P(ptr), prop_info);
 			}
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 	return 1;
 }
@@ -4214,7 +4214,7 @@ static zend_never_inline void zend_fetch_this_var(int type OPLINE_DC EXECUTE_DAT
 			ZVAL_UNDEF(result);
 			zend_throw_error(NULL, "Cannot unset $this");
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 }
 
@@ -5355,7 +5355,7 @@ static zend_never_inline zend_op_array* ZEND_FASTCALL zend_include_or_eval(zval
 				efree(eval_desc);
 			}
 			break;
-		EMPTY_SWITCH_DEFAULT_CASE()
+		default: ZEND_UNREACHABLE();
 	}
 
 	zend_tmp_string_release(tmp_inc_filename);