[Python-checkins] bpo-46640: Py_NAN now uses the C99 NAN constant (GH-31134)
vstinner
webhook-mailer at python.org
Sun Feb 6 07:13:17 EST 2022
https://github.com/python/cpython/commit/54842e4311bb0e34012d1984b42eab41eeeaea6a
commit: 54842e4311bb0e34012d1984b42eab41eeeaea6a
branch: main
author: Victor Stinner <vstinner at python.org>
committer: vstinner <vstinner at python.org>
date: 2022-02-06T13:13:04+01:00
summary:
bpo-46640: Py_NAN now uses the C99 NAN constant (GH-31134)
Building Python now requires a C99 <math.h> header file providing a
NAN constant, or the __builtin_nan() built-in function. If a platform
does not support Not-a-Number (NaN), the Py_NO_NAN macro can be
defined in the pyconfig.h file.
files:
A Misc/NEWS.d/next/Build/2022-02-04-21-26-50.bpo-46640.HXUmQp.rst
M Doc/whatsnew/3.11.rst
M Include/pymath.h
diff --git a/Doc/whatsnew/3.11.rst b/Doc/whatsnew/3.11.rst
index 1558d67d9a89f..7b5e7da8f77aa 100644
--- a/Doc/whatsnew/3.11.rst
+++ b/Doc/whatsnew/3.11.rst
@@ -604,6 +604,12 @@ Build Changes
``isinf()``, ``isnan()``, ``round()``.
(Contributed by Victor Stinner in :issue:`45440`.)
+* Building Python now requires a C99 ``<math.h>`` header file providing
+ a ``NAN`` constant, or the ``__builtin_nan()`` built-in function. If a
+ platform does not support Not-a-Number (NaN), the ``Py_NO_NAN`` macro can be
+ defined in the ``pyconfig.h`` file.
+ (Contributed by Victor Stinner in :issue:`46640`.)
+
* Freelists for object structs can now be disabled. A new :program:`configure`
option :option:`!--without-freelists` can be used to disable all freelists
except empty tuple singleton.
diff --git a/Include/pymath.h b/Include/pymath.h
index 57310fc097e73..edd0841be9259 100644
--- a/Include/pymath.h
+++ b/Include/pymath.h
@@ -51,29 +51,18 @@
#endif
/* Py_NAN
- * A value that evaluates to a NaN. On IEEE 754 platforms INF*0 or
- * INF/INF works. Define Py_NO_NAN in pyconfig.h if your platform
- * doesn't support NaNs.
+ * A value that evaluates to a quiet Not-a-Number (NaN).
+ * Define Py_NO_NAN in pyconfig.h if your platform doesn't support NaNs.
*/
#if !defined(Py_NAN) && !defined(Py_NO_NAN)
-# if !defined(__INTEL_COMPILER)
-# define Py_NAN (Py_HUGE_VAL * 0.)
-# else /* __INTEL_COMPILER */
-# if defined(ICC_NAN_STRICT)
- #pragma float_control(push)
- #pragma float_control(precise, on)
- #pragma float_control(except, on)
- Py_NO_INLINE static double __icc_nan()
- {
- return sqrt(-1.0);
- }
- #pragma float_control (pop)
-# define Py_NAN __icc_nan()
-# else /* ICC_NAN_RELAXED as default for Intel Compiler */
- static const union { unsigned char buf[8]; double __icc_nan; } __nan_store = {0,0,0,0,0,0,0xf8,0x7f};
-# define Py_NAN (__nan_store.__icc_nan)
-# endif /* ICC_NAN_STRICT */
-# endif /* __INTEL_COMPILER */
+# if _Py__has_builtin(__builtin_nan)
+ // Built-in implementation of the ISO C99 function nan(): quiet NaN.
+# define Py_NAN (__builtin_nan(""))
+#else
+ // Use C99 NAN constant: quiet Not-A-Number.
+ // NAN is a float, Py_NAN is a double: cast to double.
+# define Py_NAN ((double)NAN)
+# endif
#endif
#endif /* Py_PYMATH_H */
diff --git a/Misc/NEWS.d/next/Build/2022-02-04-21-26-50.bpo-46640.HXUmQp.rst b/Misc/NEWS.d/next/Build/2022-02-04-21-26-50.bpo-46640.HXUmQp.rst
new file mode 100644
index 0000000000000..c7381110ebbcb
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2022-02-04-21-26-50.bpo-46640.HXUmQp.rst
@@ -0,0 +1,4 @@
+Building Python now requires a C99 ``<math.h>`` header file providing a ``NAN``
+constant, or the ``__builtin_nan()`` built-in function. If a platform does not
+support Not-a-Number (NaN), the ``Py_NO_NAN`` macro can be defined in the
+``pyconfig.h`` file. Patch by Victor Stinner.
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