From 10f51543bb81cc953792270b40a9c812049e8b4c Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Tue, 1 Sep 2020 20:52:26 +0100 Subject: [PATCH] libstdc++: Add compile-time checks to__glibcxx_assert [PR 71960] MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This change evaluates __glibcxx_assert checks unconditionally when a function is being constant evaluated (when std::is_constant_evaluated() is true). If the check fails, compilation will fail with an error. If the function isn't being constant evaluated, the normal runtime check will be done if enabled by _GLIBCXX_ASSERTIONS or _GLIBCXX_DEBUG, the same as before. Tangentially, the __glibcxx_assert and _GLIBCXX_PARALLEL_ASSERT macros are changed to expand to 'do { } while (false)' when assertions are disabled, instead of expanding to nothing. This avoids -Wempty-body warnings when a disabled assertion is used in an 'if' or 'else' statement e.g. if constexpr (/* precondition is testable */) __glibcxx_assert(precondition); a.C:9:27: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body] 9 | __glibcxx_assert(precondition); | ^ libstdc++-v3/ChangeLog: PR libstdc++/71960 * include/bits/c++config (__glibcxx_assert_impl): Remove do-while so that uses of the macro need to add it. (__glibcxx_assert): Rename macro for runtime assertions to __glibcxx_assert_2. (__glibcxx_assert_1): Define macro for constexpr assertions. (__glibcxx_assert): Define macro for constexpr and runtime assertions. * include/bits/range_access.h (ranges::advance): Remove redundant precondition checks during constant evaluation. * include/parallel/base.h (_GLIBCXX_PARALLEL_ASSERT): Always use do-while in macro expansion. * include/std/ranges (iota_view::iota_view(W, B)): Remove redundant braces. --- libstdc++-v3/include/bits/c++config | 35 ++++++++++++++++++------ libstdc++-v3/include/bits/range_access.h | 10 ++----- libstdc++-v3/include/parallel/base.h | 5 ++-- libstdc++-v3/include/std/ranges | 4 +-- 4 files changed, 32 insertions(+), 22 deletions(-) diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config index de28acea6b7..badf9d01a04 100644 --- a/libstdc++-v3/include/bits/c++config +++ b/libstdc++-v3/include/bits/c++config @@ -477,19 +477,16 @@ namespace std __builtin_abort(); } } -#define __glibcxx_assert_impl(_Condition) \ - do \ - { \ - if (! (_Condition)) \ - std::__replacement_assert(__FILE__, __LINE__, __PRETTY_FUNCTION__, \ - #_Condition); \ - } while (false) +#define __glibcxx_assert_impl(_Condition) \ + if (!bool(_Condition)) \ + std::__replacement_assert(__FILE__, __LINE__, __PRETTY_FUNCTION__, \ + #_Condition) #endif #if defined(_GLIBCXX_ASSERTIONS) -# define __glibcxx_assert(_Condition) __glibcxx_assert_impl(_Condition) +# define __glibcxx_assert_2(_Condition) __glibcxx_assert_impl(_Condition) #else -# define __glibcxx_assert(_Condition) +# define __glibcxx_assert_2(_Condition) #endif // Macros for race detectors. @@ -683,6 +680,26 @@ namespace std # endif #endif // GCC +#if _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED +# define __glibcxx_assert_1(_Condition) \ + if (__builtin_is_constant_evaluated()) \ + { \ + void __failed_assertion(); \ + if (!bool(_Condition)) \ + __failed_assertion(); \ + } \ + else +#else +# define __glibcxx_assert_1(_Condition) +#endif + +# define __glibcxx_assert(_Condition) \ + do { \ + __glibcxx_assert_1(_Condition) \ + { __glibcxx_assert_2(_Condition); } \ + } while (false) + + // PSTL configuration #if __cplusplus >= 201703L diff --git a/libstdc++-v3/include/bits/range_access.h b/libstdc++-v3/include/bits/range_access.h index bafced31ea8..5c5b2fe0c6c 100644 --- a/libstdc++-v3/include/bits/range_access.h +++ b/libstdc++-v3/include/bits/range_access.h @@ -987,10 +987,7 @@ namespace ranges } else { -#ifdef __cpp_lib_is_constant_evaluated - if (std::is_constant_evaluated() && __n < 0) - throw "attempt to decrement a non-bidirectional iterator"; -#endif + // cannot decrement a non-bidirectional iterator __glibcxx_assert(__n >= 0); while (__n-- > 0) ++__it; @@ -1065,10 +1062,7 @@ namespace ranges } else { -#ifdef __cpp_lib_is_constant_evaluated - if (std::is_constant_evaluated() && __n < 0) - throw "attempt to decrement a non-bidirectional iterator"; -#endif + // cannot decrement a non-bidirectional iterator __glibcxx_assert(__n >= 0); return __n; } diff --git a/libstdc++-v3/include/parallel/base.h b/libstdc++-v3/include/parallel/base.h index 0d1c2644e8f..973a2dcd514 100644 --- a/libstdc++-v3/include/parallel/base.h +++ b/libstdc++-v3/include/parallel/base.h @@ -420,9 +420,10 @@ namespace __gnu_parallel } #if _GLIBCXX_PARALLEL_ASSERTIONS && defined(__glibcxx_assert_impl) -#define _GLIBCXX_PARALLEL_ASSERT(_Condition) __glibcxx_assert_impl(_Condition) +# define _GLIBCXX_PARALLEL_ASSERT(_Condition) \ + do { __glibcxx_assert_impl(_Condition); } while (false) #else -#define _GLIBCXX_PARALLEL_ASSERT(_Condition) +# define _GLIBCXX_PARALLEL_ASSERT(_Condition) do { } while (false) #endif } //namespace __gnu_parallel diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index 2d0017f1750..054ffe85d0f 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -860,9 +860,7 @@ namespace ranges : _M_value(__value), _M_bound(__bound) { if constexpr (totally_ordered_with<_Winc, _Bound>) - { - __glibcxx_assert( bool(__value <= __bound) ); - } + __glibcxx_assert( bool(__value <= __bound) ); } constexpr _Iterator -- 2.30.2