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From: "g.peterhoff@t-online.de" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libquadmath/109758] New: quadmath abs Date: Sat, 06 May 2023 17:44:20 +0000 [thread overview] Message-ID: <bug-109758-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109758 Bug ID: 109758 Summary: quadmath abs Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: libquadmath Assignee: unassigned at gcc dot gnu.org Reporter: g.peterhoff@t-online.de Target Milestone: --- Hello gcc-team, Problem: #include <boost/cstdfloat.hpp> #include <iostream> #include <limits> #include <cmath> using T = __float128; int main() { const T neg_nan_v = -std::numeric_limits<T>::quiet_NaN(); std::cout << neg_nan_v << std::endl; std::cout << "std::abs " << std::abs(neg_nan_v) << std::endl; std::cout << "fabsq " << fabsq(neg_nan_v) << std::endl; std::cout << "builtin " << __builtin_fabsf128(neg_nan_v) << std::endl; } -nan std::abs -nan fabsq nan builtin nan The problem can be found in bits/std_abs.h: #if !defined(__STRICT_ANSI__) && defined(_GLIBCXX_USE_FLOAT128) __extension__ inline _GLIBCXX_CONSTEXPR __float128 abs(__float128 __x) { return __x < 0 ? -__x : __x; } #endif Is this actually correct? If I compile with -U__STRICT_ANSI__ or remove/comment abs from bits/std_abs.h abs falls back to fabsq, which then also works. With std::abs(float/double/...) this problem does not occur. Wouldn't it make sense in principle to also provide a C++ header (quadmath.hpp)? #include <quadmath.h> namespace std { math-functions to_string/to_wstring to_chars/from_chars operator<< operator>> ... } thx Gero
next reply other threads:[~2023-05-06 17:44 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-06 17:44 g.peterhoff@t-online.de [this message] 2023-05-06 20:33 ` [Bug libstdc++/109758] " jakub at gcc dot gnu.org 2023-05-06 22:15 ` [Bug libstdc++/109758] std::abs(__float128) doesn't support NaN redi at gcc dot gnu.org 2023-05-06 22:48 ` g.peterhoff@t-online.de 2023-05-06 22:57 ` redi at gcc dot gnu.org 2023-05-06 23:06 ` g.peterhoff@t-online.de 2023-05-06 23:09 ` redi at gcc dot gnu.org 2023-05-07 0:09 ` g.peterhoff@t-online.de 2023-05-07 10:04 ` jakub at gcc dot gnu.org 2023-05-08 8:29 ` redi at gcc dot gnu.org 2023-05-08 8:31 ` redi at gcc dot gnu.org 2023-05-08 8:47 ` jakub at gcc dot gnu.org 2023-05-08 16:40 ` redi at gcc dot gnu.org 2023-05-11 11:55 ` cvs-commit at gcc dot gnu.org 2023-05-11 11:57 ` redi at gcc dot gnu.org 2023-05-11 12:12 ` redi at gcc dot gnu.org 2023-06-01 22:44 ` cvs-commit at gcc dot gnu.org 2023-06-01 22:45 ` redi at gcc dot gnu.org 2024-03-18 14:05 ` cvs-commit at gcc dot gnu.org 2024-03-18 14:12 ` redi at gcc dot gnu.org
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