b2348f4ced
[cpp.cond]p4:
Prior to evaluation, macro invocations in the list of preprocessing
tokens that will become the controlling constant expression are replaced
(except for those macro names modified by the 'defined' unary operator),
just as in normal text. If the token 'defined' is generated as a result
of this replacement process or use of the 'defined' unary operator does
not match one of the two specified forms prior to macro replacement, the
behavior is undefined.
This isn't an idle threat, consider this program:
#define FOO
#define BAR defined(FOO)
#if BAR
...
#else
...
#endif
clang and gcc will pick the #if branch while Visual Studio will take the
#else branch. Emit a warning about this undefined behavior.
One problem is that this also applies to function-like macros. While the
example above can be written like
#if defined(FOO) && defined(BAR)
#defined HAVE_FOO 1
#else
#define HAVE_FOO 0
#endif
there is no easy way to rewrite a function-like macro like `#define FOO(x)
(defined __foo_##x && __foo_##x)`. Function-like macros like this are used in
practice, and compilers seem to not have differing behavior in that case. So
this a default-on warning only for object-like macros. For function-like
macros, it is an extension warning that only shows up with `-pedantic`.
(But it's undefined behavior in both cases.)
llvm-svn: 258128
137 lines
3.7 KiB
C++
137 lines
3.7 KiB
C++
// RUN: %clang_cc1 -std=c++98 -verify %s
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// RUN: %clang_cc1 -std=c++11 -verify %s
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// RUN: %clang_cc1 -std=c++1y -fsized-deallocation -verify %s
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// RUN: %clang_cc1 -std=c++1y -fsized-deallocation -fconcepts-ts -DCONCEPTS_TS=1 -verify %s
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// RUN: %clang_cc1 -fcoroutines -DCOROUTINES -verify %s
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// expected-no-diagnostics
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// FIXME using `defined` in a macro has undefined behavior.
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#if __cplusplus < 201103L
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#define check(macro, cxx98, cxx11, cxx1y) cxx98 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx98
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#elif __cplusplus < 201304L
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#define check(macro, cxx98, cxx11, cxx1y) cxx11 == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx11
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#else
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#define check(macro, cxx98, cxx11, cxx1y) cxx1y == 0 ? defined(__cpp_##macro) : __cpp_##macro != cxx1y
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#endif
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#if check(binary_literals, 0, 0, 201304)
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#error "wrong value for __cpp_binary_literals"
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#endif
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#if check(digit_separators, 0, 0, 201309)
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#error "wrong value for __cpp_digit_separators"
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#endif
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#if check(init_captures, 0, 0, 201304)
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#error "wrong value for __cpp_init_captures"
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#endif
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#if check(generic_lambdas, 0, 0, 201304)
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#error "wrong value for __cpp_generic_lambdas"
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#endif
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#if check(sized_deallocation, 0, 0, 201309)
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#error "wrong value for __cpp_sized_deallocation"
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#endif
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#if check(constexpr, 0, 200704, 201304)
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#error "wrong value for __cpp_constexpr"
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#endif
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#if check(decltype_auto, 0, 0, 201304)
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#error "wrong value for __cpp_decltype_auto"
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#endif
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#if check(return_type_deduction, 0, 0, 201304)
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#error "wrong value for __cpp_return_type_deduction"
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#endif
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#if check(runtime_arrays, 0, 0, 0)
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#error "wrong value for __cpp_runtime_arrays"
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#endif
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#if check(aggregate_nsdmi, 0, 0, 201304)
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#error "wrong value for __cpp_aggregate_nsdmi"
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#endif
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#if check(variable_templates, 0, 0, 201304)
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#error "wrong value for __cpp_variable_templates"
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#endif
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#if check(unicode_characters, 0, 200704, 200704)
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#error "wrong value for __cpp_unicode_characters"
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#endif
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#if check(raw_strings, 0, 200710, 200710)
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#error "wrong value for __cpp_raw_strings"
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#endif
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#if check(unicode_literals, 0, 200710, 200710)
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#error "wrong value for __cpp_unicode_literals"
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#endif
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#if check(user_defined_literals, 0, 200809, 200809)
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#error "wrong value for __cpp_user_defined_literals"
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#endif
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#if check(lambdas, 0, 200907, 200907)
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#error "wrong value for __cpp_lambdas"
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#endif
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#if check(range_based_for, 0, 200907, 200907)
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#error "wrong value for __cpp_range_based_for"
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#endif
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#if check(static_assert, 0, 200410, 200410)
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#error "wrong value for __cpp_static_assert"
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#endif
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#if check(decltype, 0, 200707, 200707)
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#error "wrong value for __cpp_decltype"
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#endif
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#if check(attributes, 0, 200809, 200809)
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#error "wrong value for __cpp_attributes"
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#endif
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#if check(rvalue_references, 0, 200610, 200610)
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#error "wrong value for __cpp_rvalue_references"
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#endif
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#if check(variadic_templates, 0, 200704, 200704)
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#error "wrong value for __cpp_variadic_templates"
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#endif
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#if check(initializer_lists, 0, 200806, 200806)
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#error "wrong value for __cpp_initializer_lists"
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#endif
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#if check(delegating_constructors, 0, 200604, 200604)
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#error "wrong value for __cpp_delegating_constructors"
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#endif
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#if check(nsdmi, 0, 200809, 200809)
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#error "wrong value for __cpp_nsdmi"
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#endif
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#if check(inheriting_constructors, 0, 200802, 200802)
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#error "wrong value for __cpp_inheriting_constructors"
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#endif
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#if check(ref_qualifiers, 0, 200710, 200710)
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#error "wrong value for __cpp_ref_qualifiers"
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#endif
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#if check(alias_templates, 0, 200704, 200704)
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#error "wrong value for __cpp_alias_templates"
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#endif
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#if check(experimental_concepts, 0, 0, CONCEPTS_TS)
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#error "wrong value for __cpp_experimental_concepts"
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#endif
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#if (COROUTINES && !__cpp_coroutines) || (!COROUTINES && __cpp_coroutines)
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#error "wrong value for __cpp_coroutines"
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#endif
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