| 1 | /* Compile-time valid expression checker for GDB, the GNU debugger. |
| 2 | |
| 3 | Copyright (C) 2017-2020 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<typename, typename, typename = void> \ |
| 62 | struct is_valid_expression \ |
| 63 | : std::false_type {}; \ |
| 64 | \ |
| 65 | template <TYPENAMES> \ |
| 66 | struct is_valid_expression<TYPES, gdb::void_t<decltype (EXPR)>> \ |
| 67 | : std::true_type {}; \ |
| 68 | \ |
| 69 | static_assert (is_valid_expression<TYPES>::value == VALID, \ |
| 70 | ""); \ |
| 71 | \ |
| 72 | template<TYPENAMES, typename = void> \ |
| 73 | struct is_same_type \ |
| 74 | : std::is_same<EXPR_TYPE, void> {}; \ |
| 75 | \ |
| 76 | template <TYPENAMES> \ |
| 77 | struct is_same_type<TYPES, gdb::void_t<decltype (EXPR)>> \ |
| 78 | : std::is_same<EXPR_TYPE, decltype (EXPR)> {}; \ |
| 79 | \ |
| 80 | static_assert (is_same_type<TYPES>::value, ""); \ |
| 81 | } /* namespace */ |
| 82 | |
| 83 | /* A few convenience macros that support expressions involving a |
| 84 | varying numbers of types. If you need more types, feel free to add |
| 85 | another variant. */ |
| 86 | |
| 87 | #define CHECK_VALID_EXPR_1(T1, VALID, EXPR_TYPE, EXPR) \ |
| 88 | CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1), \ |
| 89 | ESC_PARENS (T1), \ |
| 90 | VALID, EXPR_TYPE, EXPR) |
| 91 | |
| 92 | #define CHECK_VALID_EXPR_2(T1, T2, VALID, EXPR_TYPE, EXPR) \ |
| 93 | CHECK_VALID_EXPR_INT (ESC_PARENS(typename T1, typename T2), \ |
| 94 | ESC_PARENS (T1, T2), \ |
| 95 | VALID, EXPR_TYPE, EXPR) |
| 96 | |
| 97 | #define CHECK_VALID_EXPR_3(T1, T2, T3, VALID, EXPR_TYPE, EXPR) \ |
| 98 | CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, typename T3), \ |
| 99 | ESC_PARENS (T1, T2, T3), \ |
| 100 | VALID, EXPR_TYPE, EXPR) |
| 101 | |
| 102 | #define CHECK_VALID_EXPR_4(T1, T2, T3, T4, VALID, EXPR_TYPE, EXPR) \ |
| 103 | CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, \ |
| 104 | typename T3, typename T4), \ |
| 105 | ESC_PARENS (T1, T2, T3, T4), \ |
| 106 | VALID, EXPR_TYPE, EXPR) |
| 107 | |
| 108 | #endif /* COMMON_VALID_EXPR_H */ |