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Try to recover from that glibc's ldexp apparently doesn't set errno on

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overflow.  Needs testing on Linux (test_long.py and test_long_future.py
especially).
This commit is contained in:
Tim Peters 2001-09-05 05:38:10 +00:00
parent e5ca6c71cd
commit 57f282a2a0
2 changed files with 22 additions and 2 deletions
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20
Include/pyport.h
View File

@ -230,6 +230,26 @@ extern "C" {
*/
#define Py_IS_INFINITY(X) ((X) && (X)*0.5 == (X))
/* Py_OVERFLOWED(X)
* Return 1 iff a libm function overflowed. Set errno to 0 before calling
* a libm function, and invoke this macro after, passing the function
* result.
* Caution:
* This isn't reliable. C99 no longer requires libm to set errno under
* any exceptional condition, but does require +- HUGE_VAL return
* values on overflow. A 754 box *probably* maps HUGE_VAL to a
* double infinity, and we're cool if that's so, unless the input
* was an infinity and an infinity is the expected result. A C89
* system sets errno to ERANGE, so we check for that too. We're
* out of luck if a C99 754 box doesn't map HUGE_VAL to +Inf, or
* if the returned result is a NaN, or if a C89 box returns HUGE_VAL
* in non-overflow cases.
* X is evaluated more than once.
*/
#define Py_OVERFLOWED(X) ((X) != 0.0 && (errno == ERANGE || \
(X) == HUGE_VAL || \
(X) == -HUGE_VAL))
/**************************************************************************
Prototypes that are missing from the standard include files on some systems
(and possibly only some versions of such systems.)

4
Objects/longobject.c
View File

@ -545,7 +545,7 @@ PyLong_AsDouble(PyObject *vv)
goto overflow;
errno = 0;
x = ldexp(x, e * SHIFT);
if (errno == ERANGE)
if (Py_OVERFLOWED(x))
goto overflow;
return x;
@ -1607,7 +1607,7 @@ long_true_divide(PyObject *v, PyObject *w)
goto overflow;
errno = 0;
ad = ldexp(ad, aexp * SHIFT);
if (ad != 0 && errno == ERANGE) /* ignore underflow to 0.0 */
if (Py_OVERFLOWED(ad)) /* ignore underflow to 0.0 */
goto overflow;
return PyFloat_FromDouble(ad);