1 /* Compile-time valid expression checker for GDB, the GNU debugger. 2 3 Copyright (C) 2017-2023 Free Software Foundation, Inc. 4 5 This file is part of GDB. 6 7 This program is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or 10 (at your option) any later version. 11 12 This program is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20 /* Helper macros used to build compile-time unit tests that make sure 21 that invalid expressions that should not compile would not compile, 22 and that expressions that should compile do compile, and have the 23 right type. This is mainly used to verify that some utility's API 24 is really as safe as intended. */ 25 26 #ifndef COMMON_VALID_EXPR_H 27 #define COMMON_VALID_EXPR_H 28 29 #include "gdbsupport/preprocessor.h" 30 #include "gdbsupport/traits.h" 31 32 /* Macro that uses SFINAE magic to detect whether the EXPR expression 33 is either valid or ill-formed, at compile time, without actually 34 producing compile-time errors. I.e., check that bad uses of the 35 types (e.g., involving mismatching types) would be caught at 36 compile time. If the expression is valid, also check whether the 37 expression has the right type. 38 39 EXPR must be defined in terms of some of the template parameters, 40 so that template substitution failure discards the overload instead 41 of causing a real compile error. TYPES is thus the list of types 42 involved in the expression, and TYPENAMES is the same list, but 43 with each element prefixed by "typename". These are passed as 44 template parameter types to the templates within the macro. 45 46 VALID is a boolean that indicates whether the expression is 47 supposed to be valid or invalid. 48 49 EXPR_TYPE is the expected type of EXPR. Only meaningful iff VALID 50 is true. If VALID is false, then you must pass "void" as expected 51 type. 52 53 Each invocation of the macro is wrapped in its own namespace to 54 avoid ODR violations. The generated namespace only includes the 55 line number, so client code should wrap sets of calls in a 56 test-specific namespace too, to fully guarantee uniqueness between 57 the multiple clients in the codebase. */ 58 #define CHECK_VALID_EXPR_INT(TYPENAMES, TYPES, VALID, EXPR_TYPE, EXPR) \ 59 namespace CONCAT (check_valid_expr, __LINE__) { \ 60 \ 61 template <TYPENAMES, typename = decltype (EXPR)> \ 62 struct archetype \ 63 { \ 64 }; \ 65 \ 66 static_assert (gdb::is_detected_exact<archetype<TYPES, EXPR_TYPE>, \ 67 archetype, TYPES>::value == VALID, \ 68 ""); \ 69 } /* namespace */ 70 71 /* A few convenience macros that support expressions involving a 72 varying numbers of types. If you need more types, feel free to add 73 another variant. */ 74 75 #define CHECK_VALID_EXPR_1(T1, VALID, EXPR_TYPE, EXPR) \ 76 CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1), \ 77 ESC_PARENS (T1), \ 78 VALID, EXPR_TYPE, EXPR) 79 80 #define CHECK_VALID_EXPR_2(T1, T2, VALID, EXPR_TYPE, EXPR) \ 81 CHECK_VALID_EXPR_INT (ESC_PARENS(typename T1, typename T2), \ 82 ESC_PARENS (T1, T2), \ 83 VALID, EXPR_TYPE, EXPR) 84 85 #define CHECK_VALID_EXPR_3(T1, T2, T3, VALID, EXPR_TYPE, EXPR) \ 86 CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, typename T3), \ 87 ESC_PARENS (T1, T2, T3), \ 88 VALID, EXPR_TYPE, EXPR) 89 90 #define CHECK_VALID_EXPR_4(T1, T2, T3, T4, VALID, EXPR_TYPE, EXPR) \ 91 CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, \ 92 typename T3, typename T4), \ 93 ESC_PARENS (T1, T2, T3, T4), \ 94 VALID, EXPR_TYPE, EXPR) 95 96 #define CHECK_VALID_EXPR_5(T1, T2, T3, T4, T5, VALID, EXPR_TYPE, EXPR) \ 97 CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, \ 98 typename T3, typename T4, \ 99 typename T5), \ 100 ESC_PARENS (T1, T2, T3, T4, T5), \ 101 VALID, EXPR_TYPE, EXPR) 102 103 #define CHECK_VALID_EXPR_6(T1, T2, T3, T4, T5, T6, \ 104 VALID, EXPR_TYPE, EXPR) \ 105 CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, \ 106 typename T3, typename T4, \ 107 typename T5, typename T6), \ 108 ESC_PARENS (T1, T2, T3, T4, T5, T6), \ 109 VALID, EXPR_TYPE, EXPR) 110 111 #endif /* COMMON_VALID_EXPR_H */ 112