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Provide a C++ version of iseqsig (bug 22377)

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In C++ mode, __MATH_TG cannot be used for defining iseqsig, because
__MATH_TG relies on __builtin_types_compatible_p, which is a C-only
builtin.  This is true when float128 is provided as an ABI-distinct type
from long double.

Moreover, the comparison macros from ISO C take two floating-point
arguments, which need not have the same type.  Choosing what underlying
function to call requires evaluating the formats of the arguments, then
selecting which is wider.  The macro __MATH_EVAL_FMT2 provides this
information, however, only the type of the macro expansion is relevant
(actually evaluating the expression would be incorrect).

This patch provides a C++ version of iseqsig, in which only the type of
__MATH_EVAL_FMT2 (__typeof or decltype) is used as a template parameter
for __iseqsig_type.  This function calls the appropriate underlying
function.

Tested for powerpc64le and x86_64.

	[BZ #22377]
	* math/Makefile [C++] (tests): Add test for iseqsig.
	* math/math.h [C++] (iseqsig): New implementation, which does
	not rely on __MATH_TG/__builtin_types_compatible_p.
	* math/test-math-iseqsig.cc: New file.
	* sysdeps/powerpc/powerpc64le/Makefile
	(CFLAGS-test-math-iseqsig.cc): New variable.
This commit is contained in:
Gabriel F. T. Gomes
2017-11-03 10:44:36 -02:00
parent 10e93d9687
commit c85e54ac6c
5 changed files with 198 additions and 5 deletions
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72
math/math.h
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@@ -1182,8 +1182,76 @@ iszero (__T __val)
/* Return X == Y but raising "invalid" and setting errno if X or Y is
a NaN. */
# define iseqsig(x, y) \
__MATH_TG (__MATH_EVAL_FMT2 (x, y), __iseqsig, ((x), (y)))
# if !defined __cplusplus || (__cplusplus < 201103L && !defined __GNUC__)
# define iseqsig(x, y) \
__MATH_TG (__MATH_EVAL_FMT2 (x, y), __iseqsig, ((x), (y)))
# else
/* In C++ mode, __MATH_TG cannot be used, because it relies on
__builtin_types_compatible_p, which is a C-only builtin. Moreover,
the comparison macros from ISO C take two floating-point arguments,
which need not have the same type. Choosing what underlying function
to call requires evaluating the formats of the arguments, then
selecting which is wider. The macro __MATH_EVAL_FMT2 provides this
information, however, only the type of the macro expansion is
relevant (actually evaluating the expression would be incorrect).
Thus, the type is used as a template parameter for __iseqsig_type,
which calls the appropriate underlying function. */
extern "C++" {
template<typename> struct __iseqsig_type;
template<> struct __iseqsig_type<float>
{
static int __call (float __x, float __y) throw ()
{
return __iseqsigf (__x, __y);
}
};
template<> struct __iseqsig_type<double>
{
static int __call (double __x, double __y) throw ()
{
return __iseqsig (__x, __y);
}
};
template<> struct __iseqsig_type<long double>
{
static int __call (double __x, double __y) throw ()
{
# ifndef __NO_LONG_DOUBLE_MATH
return __iseqsigl (__x, __y);
# else
return __iseqsig (__x, __y);
# endif
}
};
# if __HAVE_DISTINCT_FLOAT128
template<> struct __iseqsig_type<_Float128>
{
static int __call (_Float128 __x, _Float128 __y) throw ()
{
return __iseqsigf128 (__x, __y);
}
};
# endif
template<typename _T1, typename _T2>
inline int
iseqsig (_T1 __x, _T2 __y) throw ()
{
# if __cplusplus >= 201103L
typedef decltype (__MATH_EVAL_FMT2 (__x, __y)) _T3;
# else
typedef __typeof (__MATH_EVAL_FMT2 (__x, __y)) _T3;
# endif
return __iseqsig_type<_T3>::__call (__x, __y);
}
} /* extern "C++" */
# endif /* __cplusplus */
#endif
__END_DECLS