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A while ago, back when GDB was a C program, the sect_offset and cu_offset types were made structs in order to prevent incorrect mixing of those offsets. Now that we require C++11, we can make them integers again, while keeping the safety, by exploiting "enum class". We can add a bit more safety, even, by defining operators that the types _should_ support, helping making the suspicious uses stand out more. Getting at the underlying type is done with the new to_underlying function added by the previous patch, which also helps better spot where do we need to step out of the safety net. Mostly, that's around parsing the DWARF, and when we print the offset for complaint/debug purposes. But there are other occasional uses. Since we have to define the sect_offset/cu_offset types in a header anyway, I went ahead and generalized/library-fied the idea of "offset" types, making it trivial to add more such types if we find a use. See common/offset-type.h and the DEFINE_OFFSET_TYPE macro. I needed a couple generaly-useful preprocessor bits (e.g., yet another CONCAT implementation), so I started a new common/preprocessor.h file. I included units tests covering the "offset" types API. These are mostly compile-time tests, using SFINAE to check that expressions that shouldn't compile (e.g., comparing unrelated offset types) really are invalid and would fail to compile. This same idea appeared in my pending enum-flags revamp from a few months ago (though this version is a bit further modernized compared to what I had posted), and I plan on reusing the "check valid expression" bits added here in that series, so I went ahead and defined the CHECK_VALID_EXPR macro in its own header -- common/valid-expr.h. I think that's nicer regardless. I was borderline between calling the new types "offset" types, or "index" types, BTW. I stuck with "offset" simply because that's what we're already calling them, mostly. gdb/ChangeLog: 2017-04-04 Pedro Alves <palves@redhat.com> * Makefile.in (SUBDIR_UNITTESTS_SRCS): Add unittests/offset-type-selftests.c. (SUBDIR_UNITTESTS_OBS): Add offset-type-selftests.o. * common/offset-type.h: New file. * common/preprocessor.h: New file. * common/traits.h: New file. * common/valid-expr.h: New file. * dwarf2expr.c: Include "common/underlying.h". Adjust to use sect_offset and cu_offset strong typedefs throughout. * dwarf2expr.h: Adjust to use sect_offset and cu_offset strong typedefs throughout. * dwarf2loc.c: Include "common/underlying.h". Adjust to use sect_offset and cu_offset strong typedefs throughout. * dwarf2read.c: Adjust to use sect_offset and cu_offset strong typedefs throughout. * gdbtypes.h: Include "common/offset-type.h". (cu_offset): Now an offset type (strong typedef) instead of a struct. (sect_offset): Likewise. (union call_site_parameter_u): Rename "param_offset" field to "param_cu_off". * unittests/offset-type-selftests.c: New file.
109 lines
4.3 KiB
C++
109 lines
4.3 KiB
C++
/* Compile-time valid expression checker for GDB, the GNU debugger.
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Copyright (C) 2017 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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/* Helper macros used to build compile-time unit tests that make sure
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that invalid expressions that should not compile would not compile,
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and that expressions that should compile do compile, and have the
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right type. This is mainly used to verify that some utility's API
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is really as safe as intended. */
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#ifndef COMMON_VALID_EXPR_H
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#define COMMON_VALID_EXPR_H
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#include "common/preprocessor.h"
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#include "common/traits.h"
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/* Macro that uses SFINAE magic to detect whether the EXPR expression
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is either valid or ill-formed, at compile time, without actually
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producing compile-time errors. I.e., check that bad uses of the
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types (e.g., involving mismatching types) would be caught at
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compile time. If the expression is valid, also check whether the
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expression has the right type.
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EXPR must be defined in terms of some of the template parameters,
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so that template substitution failure discards the overload instead
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of causing a real compile error. TYPES is thus the list of types
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involved in the expression, and TYPENAMES is the same list, but
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with each element prefixed by "typename". These are passed as
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template parameter types to the templates within the macro.
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VALID is a boolean that indicates whether the expression is
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supposed to be valid or invalid.
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EXPR_TYPE is the expected type of EXPR. Only meaningful iff VALID
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is true. If VALID is false, then you must pass "void" as expected
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type.
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Each invocation of the macro is wrapped in its own namespace to
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avoid ODR violations. The generated namespace only includes the
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line number, so client code should wrap sets of calls in a
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test-specific namespace too, to fully guarantee uniqueness between
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the multiple clients in the codebase. */
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#define CHECK_VALID_EXPR_INT(TYPENAMES, TYPES, VALID, EXPR_TYPE, EXPR) \
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namespace CONCAT (check_valid_expr, __LINE__) { \
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\
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template<typename, typename, typename = void> \
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struct is_valid_expression \
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: std::false_type {}; \
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\
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template <TYPENAMES> \
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struct is_valid_expression<TYPES, gdb::void_t<decltype (EXPR)>> \
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: std::true_type {}; \
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\
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static_assert (is_valid_expression<TYPES>::value == VALID, \
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""); \
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\
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template<TYPENAMES, typename = void> \
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struct is_same_type \
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: std::is_same<EXPR_TYPE, void> {}; \
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\
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template <TYPENAMES> \
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struct is_same_type<TYPES, gdb::void_t<decltype (EXPR)>> \
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: std::is_same<EXPR_TYPE, decltype (EXPR)> {}; \
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\
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static_assert (is_same_type<TYPES>::value, ""); \
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} /* namespace */
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/* A few convenience macros that support expressions involving a
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varying numbers of types. If you need more types, feel free to add
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another variant. */
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#define CHECK_VALID_EXPR_1(T1, VALID, EXPR_TYPE, EXPR) \
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CHECK_VALID_EXPR_INT (ESC (typename T1), \
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ESC (T1), \
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VALID, EXPR_TYPE, EXPR)
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#define CHECK_VALID_EXPR_2(T1, T2, VALID, EXPR_TYPE, EXPR) \
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CHECK_VALID_EXPR_INT (ESC (typename T1, typename T2), \
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ESC (T1, T2), \
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VALID, EXPR_TYPE, EXPR)
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#define CHECK_VALID_EXPR_3(T1, T2, T3, VALID, EXPR_TYPE, EXPR) \
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CHECK_VALID_EXPR_INT (ESC (typename T1, typename T2, typename T3), \
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ESC (T1, T2, T3), \
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VALID, EXPR_TYPE, EXPR)
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#define CHECK_VALID_EXPR_4(T1, T2, T3, T4, VALID, EXPR_TYPE, EXPR) \
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CHECK_VALID_EXPR_INT (ESC (typename T1, typename T2, \
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typename T3, typename T4), \
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ESC (T1, T2, T3, T4), \
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VALID, EXPR_TYPE, EXPR)
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#endif /* COMMON_VALID_EXPR_H */
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