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Issue #4575: fix Py_IS_INFINITY macro to work correctly on x87 FPUs.

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It now forces its argument to double before testing for infinity.
This commit is contained in:
Mark Dickinson 2009-02-09 14:18:43 +00:00
parent b20af944d2
commit c97c9096ed
3 changed files with 40 additions and 5 deletions
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29
Include/pymath.h
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@ -77,6 +77,21 @@ extern double copysign(double, double);
#define Py_MATH_E 2.7182818284590452354
#endif
/* On x86, Py_FORCE_DOUBLE forces a floating-point number out of an x87 FPU
register and into a 64-bit memory location, rounding from extended
precision to double precision in the process. On other platforms it does
nothing. */
/* we take double rounding as evidence of x87 usage */
#ifndef Py_FORCE_DOUBLE
# ifdef X87_DOUBLE_ROUNDING
PyAPI_FUNC(double) _Py_force_double(double);
# define Py_FORCE_DOUBLE(X) (_Py_force_double(X))
# else
# define Py_FORCE_DOUBLE(X) (X)
# endif
#endif
/* Py_IS_NAN(X)
* Return 1 if float or double arg is a NaN, else 0.
* Caution:
@ -101,14 +116,18 @@ extern double copysign(double, double);
* This implementation may set the underflow flag if |X| is very small;
* it really can't be implemented correctly (& easily) before C99.
* Override in pyconfig.h if you have a better spelling on your platform.
* Py_FORCE_DOUBLE is used to avoid getting false negatives from a
* non-infinite value v sitting in an 80-bit x87 register such that
* v becomes infinite when spilled from the register to 64-bit memory.
* Note: PC/pyconfig.h defines Py_IS_INFINITY as _isinf
*/
#ifndef Py_IS_INFINITY
#if defined HAVE_DECL_ISINF && HAVE_DECL_ISINF == 1
#define Py_IS_INFINITY(X) isinf(X)
#else
#define Py_IS_INFINITY(X) ((X) && (X)*0.5 == (X))
#endif
# if defined HAVE_DECL_ISINF && HAVE_DECL_ISINF == 1
# define Py_IS_INFINITY(X) isinf(X)
# else
# define Py_IS_INFINITY(X) ((X) && \
(Py_FORCE_DOUBLE(X)*0.5 == Py_FORCE_DOUBLE(X)))
# endif
#endif
/* Py_IS_FINITE(X)