aa0235dfde
All representations of floating-point numbers in types with IEC 60559 binary exchange format are canonical. On the other hand, types with IEC 60559 extended formats, such as those implemented under ldbl-96 and ldbl-128ibm, contain representations that are not canonical. TS 18661-1 introduced the type-generic macro iscanonical, which returns whether a floating-point value is canonical or not. In Glibc, this type-generic macro is implemented using the macro __MATH_TG, which, when support for float128 is enabled, relies on __builtin_types_compatible_p to select between floating-point types. However, this use of iscanonical breaks C++ applications, because the builtin is only available in C mode. This patch provides a C++ implementation of iscanonical that relies on function overloading, rather than builtins, to select between floating-point types. Unlike the C++ implementations for iszero and issignaling, this implementation ignores __NO_LONG_DOUBLE_MATH. The double type always matches IEC 60559 double format, which is always canonical. Thus, when double and long double are the same (__NO_LONG_DOUBLE_MATH), iscanonical always returns 1 and is not implemented with __MATH_TG. Tested for powerpc64, powerpc64le and x86_64. [BZ #22235] * math/math.h: Trivial fix for unbalanced parentheses in comment. * math/Makefile [CXX] (tests): Add test-math-iscanonical.cc. (CFLAGS-test-math-iscanonical.cc): New variable. * math/test-math-iscanonical.cc: New file. * sysdeps/ieee754/ldbl-96/bits/iscanonical.h (iscanonical): Provide a C++ implementation based on function overloading, rather than using __MATH_TG, which uses C-only builtins. * sysdeps/ieee754/ldbl-128ibm/bits/iscanonical.h (iscanonical): Likewise. * sysdeps/powerpc/powerpc64le/Makefile (CFLAGS-test-math-iscanonical.cc): New variable.
55 lines
2.4 KiB
C
55 lines
2.4 KiB
C
/* Define iscanonical macro. ldbl-96 version.
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Copyright (C) 2016-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#ifndef _MATH_H
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# error "Never use <bits/iscanonical.h> directly; include <math.h> instead."
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#endif
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extern int __iscanonicall (long double __x)
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__THROW __attribute__ ((__const__));
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#define __iscanonicalf(x) ((void) (__typeof (x)) (x), 1)
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#define __iscanonical(x) ((void) (__typeof (x)) (x), 1)
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#if __HAVE_DISTINCT_FLOAT128
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# define __iscanonicalf128(x) ((void) (__typeof (x)) (x), 1)
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#endif
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/* Return nonzero value if X is canonical. In IEEE interchange binary
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formats, all values are canonical, but the argument must still be
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converted to its semantic type for any exceptions arising from the
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conversion, before being discarded; in extended precision, there
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are encodings that are not consistently handled as corresponding to
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any particular value of the type, and we return 0 for those. */
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#ifndef __cplusplus
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# define iscanonical(x) __MATH_TG ((x), __iscanonical, (x))
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#else
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/* In C++ mode, __MATH_TG cannot be used, because it relies on
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__builtin_types_compatible_p, which is a C-only builtin. On the
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other hand, overloading provides the means to distinguish between
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the floating-point types. The overloading resolution will match
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the correct parameter (regardless of type qualifiers (i.e.: const
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and volatile)). */
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extern "C++" {
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inline int iscanonical (float __val) { return __iscanonicalf (__val); }
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inline int iscanonical (double __val) { return __iscanonical (__val); }
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inline int iscanonical (long double __val) { return __iscanonicall (__val); }
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# if __HAVE_DISTINCT_FLOAT128
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inline int iscanonical (_Float128 __val) { return __iscanonicalf128 (__val); }
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# endif
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}
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#endif /* __cplusplus */
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