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Diffstat (limited to 'gdbsupport/valid-expr.h')
| -rw-r--r-- | gdbsupport/valid-expr.h | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/gdbsupport/valid-expr.h b/gdbsupport/valid-expr.h new file mode 100644 index 00000000000..b1c84468147 --- /dev/null +++ b/gdbsupport/valid-expr.h @@ -0,0 +1,108 @@ +/* Compile-time valid expression checker for GDB, the GNU debugger. + + Copyright (C) 2017-2020 Free Software Foundation, Inc. + + This file is part of GDB. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +/* Helper macros used to build compile-time unit tests that make sure + that invalid expressions that should not compile would not compile, + and that expressions that should compile do compile, and have the + right type. This is mainly used to verify that some utility's API + is really as safe as intended. */ + +#ifndef COMMON_VALID_EXPR_H +#define COMMON_VALID_EXPR_H + +#include "gdbsupport/preprocessor.h" +#include "gdbsupport/traits.h" + +/* Macro that uses SFINAE magic to detect whether the EXPR expression + is either valid or ill-formed, at compile time, without actually + producing compile-time errors. I.e., check that bad uses of the + types (e.g., involving mismatching types) would be caught at + compile time. If the expression is valid, also check whether the + expression has the right type. + + EXPR must be defined in terms of some of the template parameters, + so that template substitution failure discards the overload instead + of causing a real compile error. TYPES is thus the list of types + involved in the expression, and TYPENAMES is the same list, but + with each element prefixed by "typename". These are passed as + template parameter types to the templates within the macro. + + VALID is a boolean that indicates whether the expression is + supposed to be valid or invalid. + + EXPR_TYPE is the expected type of EXPR. Only meaningful iff VALID + is true. If VALID is false, then you must pass "void" as expected + type. + + Each invocation of the macro is wrapped in its own namespace to + avoid ODR violations. The generated namespace only includes the + line number, so client code should wrap sets of calls in a + test-specific namespace too, to fully guarantee uniqueness between + the multiple clients in the codebase. */ +#define CHECK_VALID_EXPR_INT(TYPENAMES, TYPES, VALID, EXPR_TYPE, EXPR) \ + namespace CONCAT (check_valid_expr, __LINE__) { \ + \ + template<typename, typename, typename = void> \ + struct is_valid_expression \ + : std::false_type {}; \ + \ + template <TYPENAMES> \ + struct is_valid_expression<TYPES, gdb::void_t<decltype (EXPR)>> \ + : std::true_type {}; \ + \ + static_assert (is_valid_expression<TYPES>::value == VALID, \ + ""); \ + \ + template<TYPENAMES, typename = void> \ + struct is_same_type \ + : std::is_same<EXPR_TYPE, void> {}; \ + \ + template <TYPENAMES> \ + struct is_same_type<TYPES, gdb::void_t<decltype (EXPR)>> \ + : std::is_same<EXPR_TYPE, decltype (EXPR)> {}; \ + \ + static_assert (is_same_type<TYPES>::value, ""); \ + } /* namespace */ + +/* A few convenience macros that support expressions involving a + varying numbers of types. If you need more types, feel free to add + another variant. */ + +#define CHECK_VALID_EXPR_1(T1, VALID, EXPR_TYPE, EXPR) \ + CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1), \ + ESC_PARENS (T1), \ + VALID, EXPR_TYPE, EXPR) + +#define CHECK_VALID_EXPR_2(T1, T2, VALID, EXPR_TYPE, EXPR) \ + CHECK_VALID_EXPR_INT (ESC_PARENS(typename T1, typename T2), \ + ESC_PARENS (T1, T2), \ + VALID, EXPR_TYPE, EXPR) + +#define CHECK_VALID_EXPR_3(T1, T2, T3, VALID, EXPR_TYPE, EXPR) \ + CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, typename T3), \ + ESC_PARENS (T1, T2, T3), \ + VALID, EXPR_TYPE, EXPR) + +#define CHECK_VALID_EXPR_4(T1, T2, T3, T4, VALID, EXPR_TYPE, EXPR) \ + CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, \ + typename T3, typename T4), \ + ESC_PARENS (T1, T2, T3, T4), \ + VALID, EXPR_TYPE, EXPR) + +#endif /* COMMON_VALID_EXPR_H */ |