[Python-checkins] bpo-45548: Remove _math.c workarounds for pre-C99 libm (GH-29179)
miss-islington
webhook-mailer at python.org
Mon Oct 25 04:25:47 EDT 2021
https://github.com/python/cpython/commit/fa26245a1c1aa938cce391348d6bd879da357522
commit: fa26245a1c1aa938cce391348d6bd879da357522
branch: main
author: Christian Heimes <christian at python.org>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2021-10-25T01:25:27-07:00
summary:
bpo-45548: Remove _math.c workarounds for pre-C99 libm (GH-29179)
The :mod:`math` and :mod:`cmath` implementation now require a C99 compatible
``libm`` and no longer ship with workarounds for missing acosh, asinh,
expm1, and log1p functions.
The changeset also removes ``_math.c`` and moves the last remaining
workaround into ``_math.h``. This simplifies static builds with
``Modules/Setup`` and resolves symbol conflicts.
Co-authored-by: Mark Dickinson <mdickinson at enthought.com>
Co-authored-by: Brett Cannon <brett at python.org>
Signed-off-by: Christian Heimes <christian at python.org>
files:
A Misc/NEWS.d/next/Build/2021-10-24-21-49-49.bpo-45548.UWx0UC.rst
D Modules/_math.c
M Makefile.pre.in
M Modules/Setup
M Modules/_math.h
M Modules/cmathmodule.c
M Modules/mathmodule.c
M PCbuild/pythoncore.vcxproj
M PCbuild/pythoncore.vcxproj.filters
M configure
M configure.ac
M setup.py
diff --git a/Makefile.pre.in b/Makefile.pre.in
index f03f535f6faa6..4ee8fddbe14ee 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -611,10 +611,6 @@ pybuilddir.txt: $(BUILDPYTHON)
exit 1 ; \
fi
-# This is shared by the math and cmath modules
-Modules/_math.o: Modules/_math.c Modules/_math.h
- $(CC) -c $(CCSHARED) $(PY_CORE_CFLAGS) -o $@ $<
-
# blake2s is auto-generated from blake2b
$(srcdir)/Modules/_blake2/blake2s_impl.c: $(srcdir)/Modules/_blake2/blake2b_impl.c $(srcdir)/Modules/_blake2/blake2b2s.py
$(PYTHON_FOR_REGEN) $(srcdir)/Modules/_blake2/blake2b2s.py
@@ -625,7 +621,7 @@ $(srcdir)/Modules/_blake2/blake2s_impl.c: $(srcdir)/Modules/_blake2/blake2b_impl
# -s, --silent or --quiet is always the first char.
# Under BSD make, MAKEFLAGS might be " -s -v x=y".
# Ignore macros passed by GNU make, passed after --
-sharedmods: $(BUILDPYTHON) pybuilddir.txt Modules/_math.o
+sharedmods: $(BUILDPYTHON) pybuilddir.txt
@case "`echo X $$MAKEFLAGS | sed 's/^X //;s/ -- .*//'`" in \
*\ -s*|s*) quiet="-q";; \
*) quiet="";; \
diff --git a/Misc/NEWS.d/next/Build/2021-10-24-21-49-49.bpo-45548.UWx0UC.rst b/Misc/NEWS.d/next/Build/2021-10-24-21-49-49.bpo-45548.UWx0UC.rst
new file mode 100644
index 0000000000000..15fd56615ffa9
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2021-10-24-21-49-49.bpo-45548.UWx0UC.rst
@@ -0,0 +1,3 @@
+The :mod:`math` and :mod:`cmath` implementation now require a C99 compatible
+``libm`` and no longer ship with workarounds for missing acosh, asinh, atanh,
+expm1, and log1p functions.
diff --git a/Modules/Setup b/Modules/Setup
index d06d733fc9cbb..99c7d4e909e18 100644
--- a/Modules/Setup
+++ b/Modules/Setup
@@ -171,8 +171,8 @@ time timemodule.c
#array arraymodule.c
#audioop audioop.c
#binascii binascii.c
-#cmath cmathmodule.c _math.c # -lm
-#math mathmodule.c _math.c # -lm
+#cmath cmathmodule.c # -lm
+#math mathmodule.c # -lm
#pyexpat -I$(srcdir)/Modules/expat expat/xmlparse.c expat/xmlrole.c expat/xmltok.c pyexpat.c
#unicodedata unicodedata.c
diff --git a/Modules/_math.c b/Modules/_math.c
deleted file mode 100644
index c1936a1088a24..0000000000000
--- a/Modules/_math.c
+++ /dev/null
@@ -1,270 +0,0 @@
-/* Definitions of some C99 math library functions, for those platforms
- that don't implement these functions already. */
-
-#ifndef Py_BUILD_CORE_BUILTIN
-# define Py_BUILD_CORE_MODULE 1
-#endif
-
-#include "Python.h"
-#include <float.h>
-#include "_math.h"
-
-/* The following copyright notice applies to the original
- implementations of acosh, asinh and atanh. */
-
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
-
-#if !defined(HAVE_ACOSH) || !defined(HAVE_ASINH)
-static const double ln2 = 6.93147180559945286227E-01;
-static const double two_pow_p28 = 268435456.0; /* 2**28 */
-#endif
-#if !defined(HAVE_ASINH) || !defined(HAVE_ATANH)
-static const double two_pow_m28 = 3.7252902984619141E-09; /* 2**-28 */
-#endif
-#if !defined(HAVE_ATANH) && !defined(Py_NAN)
-static const double zero = 0.0;
-#endif
-
-
-#ifndef HAVE_ACOSH
-/* acosh(x)
- * Method :
- * Based on
- * acosh(x) = log [ x + sqrt(x*x-1) ]
- * we have
- * acosh(x) := log(x)+ln2, if x is large; else
- * acosh(x) := log(2x-1/(sqrt(x*x-1)+x)) if x>2; else
- * acosh(x) := log1p(t+sqrt(2.0*t+t*t)); where t=x-1.
- *
- * Special cases:
- * acosh(x) is NaN with signal if x<1.
- * acosh(NaN) is NaN without signal.
- */
-
-double
-_Py_acosh(double x)
-{
- if (Py_IS_NAN(x)) {
- return x+x;
- }
- if (x < 1.) { /* x < 1; return a signaling NaN */
- errno = EDOM;
-#ifdef Py_NAN
- return Py_NAN;
-#else
- return (x-x)/(x-x);
-#endif
- }
- else if (x >= two_pow_p28) { /* x > 2**28 */
- if (Py_IS_INFINITY(x)) {
- return x+x;
- }
- else {
- return log(x) + ln2; /* acosh(huge)=log(2x) */
- }
- }
- else if (x == 1.) {
- return 0.0; /* acosh(1) = 0 */
- }
- else if (x > 2.) { /* 2 < x < 2**28 */
- double t = x * x;
- return log(2.0 * x - 1.0 / (x + sqrt(t - 1.0)));
- }
- else { /* 1 < x <= 2 */
- double t = x - 1.0;
- return m_log1p(t + sqrt(2.0 * t + t * t));
- }
-}
-#endif /* HAVE_ACOSH */
-
-
-#ifndef HAVE_ASINH
-/* asinh(x)
- * Method :
- * Based on
- * asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
- * we have
- * asinh(x) := x if 1+x*x=1,
- * := sign(x)*(log(x)+ln2) for large |x|, else
- * := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
- * := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
- */
-
-double
-_Py_asinh(double x)
-{
- double w;
- double absx = fabs(x);
-
- if (Py_IS_NAN(x) || Py_IS_INFINITY(x)) {
- return x+x;
- }
- if (absx < two_pow_m28) { /* |x| < 2**-28 */
- return x; /* return x inexact except 0 */
- }
- if (absx > two_pow_p28) { /* |x| > 2**28 */
- w = log(absx) + ln2;
- }
- else if (absx > 2.0) { /* 2 < |x| < 2**28 */
- w = log(2.0 * absx + 1.0 / (sqrt(x * x + 1.0) + absx));
- }
- else { /* 2**-28 <= |x| < 2= */
- double t = x*x;
- w = m_log1p(absx + t / (1.0 + sqrt(1.0 + t)));
- }
- return copysign(w, x);
-
-}
-#endif /* HAVE_ASINH */
-
-
-#ifndef HAVE_ATANH
-/* atanh(x)
- * Method :
- * 1.Reduced x to positive by atanh(-x) = -atanh(x)
- * 2.For x>=0.5
- * 1 2x x
- * atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * -------)
- * 2 1 - x 1 - x
- *
- * For x<0.5
- * atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
- *
- * Special cases:
- * atanh(x) is NaN if |x| >= 1 with signal;
- * atanh(NaN) is that NaN with no signal;
- *
- */
-
-double
-_Py_atanh(double x)
-{
- double absx;
- double t;
-
- if (Py_IS_NAN(x)) {
- return x+x;
- }
- absx = fabs(x);
- if (absx >= 1.) { /* |x| >= 1 */
- errno = EDOM;
-#ifdef Py_NAN
- return Py_NAN;
-#else
- return x / zero;
-#endif
- }
- if (absx < two_pow_m28) { /* |x| < 2**-28 */
- return x;
- }
- if (absx < 0.5) { /* |x| < 0.5 */
- t = absx+absx;
- t = 0.5 * m_log1p(t + t*absx / (1.0 - absx));
- }
- else { /* 0.5 <= |x| <= 1.0 */
- t = 0.5 * m_log1p((absx + absx) / (1.0 - absx));
- }
- return copysign(t, x);
-}
-#endif /* HAVE_ATANH */
-
-
-#ifndef HAVE_EXPM1
-/* Mathematically, expm1(x) = exp(x) - 1. The expm1 function is designed
- to avoid the significant loss of precision that arises from direct
- evaluation of the expression exp(x) - 1, for x near 0. */
-
-double
-_Py_expm1(double x)
-{
- /* For abs(x) >= log(2), it's safe to evaluate exp(x) - 1 directly; this
- also works fine for infinities and nans.
-
- For smaller x, we can use a method due to Kahan that achieves close to
- full accuracy.
- */
-
- if (fabs(x) < 0.7) {
- double u;
- u = exp(x);
- if (u == 1.0)
- return x;
- else
- return (u - 1.0) * x / log(u);
- }
- else
- return exp(x) - 1.0;
-}
-#endif /* HAVE_EXPM1 */
-
-
-/* log1p(x) = log(1+x). The log1p function is designed to avoid the
- significant loss of precision that arises from direct evaluation when x is
- small. */
-
-double
-_Py_log1p(double x)
-{
-#ifdef HAVE_LOG1P
- /* Some platforms supply a log1p function but don't respect the sign of
- zero: log1p(-0.0) gives 0.0 instead of the correct result of -0.0.
-
- To save fiddling with configure tests and platform checks, we handle the
- special case of zero input directly on all platforms.
- */
- if (x == 0.0) {
- return x;
- }
- else {
- return log1p(x);
- }
-#else
- /* For x small, we use the following approach. Let y be the nearest float
- to 1+x, then
-
- 1+x = y * (1 - (y-1-x)/y)
-
- so log(1+x) = log(y) + log(1-(y-1-x)/y). Since (y-1-x)/y is tiny, the
- second term is well approximated by (y-1-x)/y. If abs(x) >=
- DBL_EPSILON/2 or the rounding-mode is some form of round-to-nearest
- then y-1-x will be exactly representable, and is computed exactly by
- (y-1)-x.
-
- If abs(x) < DBL_EPSILON/2 and the rounding mode is not known to be
- round-to-nearest then this method is slightly dangerous: 1+x could be
- rounded up to 1+DBL_EPSILON instead of down to 1, and in that case
- y-1-x will not be exactly representable any more and the result can be
- off by many ulps. But this is easily fixed: for a floating-point
- number |x| < DBL_EPSILON/2., the closest floating-point number to
- log(1+x) is exactly x.
- */
-
- double y;
- if (fabs(x) < DBL_EPSILON / 2.) {
- return x;
- }
- else if (-0.5 <= x && x <= 1.) {
- /* WARNING: it's possible that an overeager compiler
- will incorrectly optimize the following two lines
- to the equivalent of "return log(1.+x)". If this
- happens, then results from log1p will be inaccurate
- for small x. */
- y = 1.+x;
- return log(y) - ((y - 1.) - x) / y;
- }
- else {
- /* NaNs and infinities should end up here */
- return log(1.+x);
- }
-#endif /* ifdef HAVE_LOG1P */
-}
-
diff --git a/Modules/_math.h b/Modules/_math.h
index 398b7e8874af0..4a6bc223ef5fb 100644
--- a/Modules/_math.h
+++ b/Modules/_math.h
@@ -1,41 +1,24 @@
-#ifdef HAVE_ACOSH
-# define m_acosh acosh
-#else
-/* if the system doesn't have acosh, use the substitute
- function defined in Modules/_math.c. */
-double _Py_acosh(double x);
-# define m_acosh _Py_acosh
-#endif
+/* log1p(x) = log(1+x). The log1p function is designed to avoid the
+ significant loss of precision that arises from direct evaluation when x is
+ small. Use the substitute from _math.h on all platforms: it includes
+ workarounds for buggy handling of zeros.
+ */
-#ifdef HAVE_ASINH
-# define m_asinh asinh
-#else
-/* if the system doesn't have asinh, use the substitute
- function defined in Modules/_math.c. */
-double _Py_asinh(double x);
-# define m_asinh _Py_asinh
-#endif
+static double
+_Py_log1p(double x)
+{
+ /* Some platforms supply a log1p function but don't respect the sign of
+ zero: log1p(-0.0) gives 0.0 instead of the correct result of -0.0.
-#ifdef HAVE_ATANH
-# define m_atanh atanh
-#else
-/* if the system doesn't have atanh, use the substitute
- function defined in Modules/_math.c. */
-double _Py_atanh(double x);
-#define m_atanh _Py_atanh
-#endif
+ To save fiddling with configure tests and platform checks, we handle the
+ special case of zero input directly on all platforms.
+ */
+ if (x == 0.0) {
+ return x;
+ }
+ else {
+ return log1p(x);
+ }
+}
-#ifdef HAVE_EXPM1
-# define m_expm1 expm1
-#else
-/* if the system doesn't have expm1, use the substitute
- function defined in Modules/_math.c. */
-double _Py_expm1(double x);
-#define m_expm1 _Py_expm1
-#endif
-
-double _Py_log1p(double x);
-
-/* Use the substitute from _math.c on all platforms:
- it includes workarounds for buggy handling of zeros. */
#define m_log1p _Py_log1p
diff --git a/Modules/cmathmodule.c b/Modules/cmathmodule.c
index 0e0489c5fe2d7..281d3937e2656 100644
--- a/Modules/cmathmodule.c
+++ b/Modules/cmathmodule.c
@@ -8,11 +8,13 @@
#include "Python.h"
#include "pycore_dtoa.h"
-#include "_math.h"
/* we need DBL_MAX, DBL_MIN, DBL_EPSILON, DBL_MANT_DIG and FLT_RADIX from
float.h. We assume that FLT_RADIX is either 2 or 16. */
#include <float.h>
+/* For _Py_log1p with workarounds for buggy handling of zeros. */
+#include "_math.h"
+
#include "clinic/cmathmodule.c.h"
/*[clinic input]
module cmath
@@ -246,7 +248,7 @@ cmath_acos_impl(PyObject *module, Py_complex z)
s2.imag = z.imag;
s2 = cmath_sqrt_impl(module, s2);
r.real = 2.*atan2(s1.real, s2.real);
- r.imag = m_asinh(s2.real*s1.imag - s2.imag*s1.real);
+ r.imag = asinh(s2.real*s1.imag - s2.imag*s1.real);
}
errno = 0;
return r;
@@ -280,7 +282,7 @@ cmath_acosh_impl(PyObject *module, Py_complex z)
s2.real = z.real + 1.;
s2.imag = z.imag;
s2 = cmath_sqrt_impl(module, s2);
- r.real = m_asinh(s1.real*s2.real + s1.imag*s2.imag);
+ r.real = asinh(s1.real*s2.real + s1.imag*s2.imag);
r.imag = 2.*atan2(s1.imag, s2.real);
}
errno = 0;
@@ -340,7 +342,7 @@ cmath_asinh_impl(PyObject *module, Py_complex z)
s2.real = 1.-z.imag;
s2.imag = z.real;
s2 = cmath_sqrt_impl(module, s2);
- r.real = m_asinh(s1.real*s2.imag-s2.real*s1.imag);
+ r.real = asinh(s1.real*s2.imag-s2.real*s1.imag);
r.imag = atan2(z.imag, s1.real*s2.real-s1.imag*s2.imag);
}
errno = 0;
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 6c12a4e70ddf2..67669f19bc28c 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -61,6 +61,9 @@ raised for division by zero and mod by zero.
#include "pycore_call.h" // _PyObject_CallNoArgs()
#include "pycore_dtoa.h" // _Py_dg_infinity()
#include "pycore_long.h" // _PyLong_GetZero()
+/* For DBL_EPSILON in _math.h */
+#include <float.h>
+/* For _Py_log1p with workarounds for buggy handling of zeros. */
#include "_math.h"
#include "clinic/mathmodule.c.h"
@@ -1166,14 +1169,14 @@ FUNC1(acos, acos, 0,
"acos($module, x, /)\n--\n\n"
"Return the arc cosine (measured in radians) of x.\n\n"
"The result is between 0 and pi.")
-FUNC1(acosh, m_acosh, 0,
+FUNC1(acosh, acosh, 0,
"acosh($module, x, /)\n--\n\n"
"Return the inverse hyperbolic cosine of x.")
FUNC1(asin, asin, 0,
"asin($module, x, /)\n--\n\n"
"Return the arc sine (measured in radians) of x.\n\n"
"The result is between -pi/2 and pi/2.")
-FUNC1(asinh, m_asinh, 0,
+FUNC1(asinh, asinh, 0,
"asinh($module, x, /)\n--\n\n"
"Return the inverse hyperbolic sine of x.")
FUNC1(atan, atan, 0,
@@ -1184,7 +1187,7 @@ FUNC2(atan2, m_atan2,
"atan2($module, y, x, /)\n--\n\n"
"Return the arc tangent (measured in radians) of y/x.\n\n"
"Unlike atan(y/x), the signs of both x and y are considered.")
-FUNC1(atanh, m_atanh, 0,
+FUNC1(atanh, atanh, 0,
"atanh($module, x, /)\n--\n\n"
"Return the inverse hyperbolic tangent of x.")
FUNC1(cbrt, cbrt, 0,
@@ -1245,7 +1248,7 @@ FUNC1A(erfc, m_erfc,
FUNC1(exp, exp, 1,
"exp($module, x, /)\n--\n\n"
"Return e raised to the power of x.")
-FUNC1(expm1, m_expm1, 1,
+FUNC1(expm1, expm1, 1,
"expm1($module, x, /)\n--\n\n"
"Return exp(x)-1.\n\n"
"This function avoids the loss of precision involved in the direct "
diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
index 1b484be5e7a2f..646bc8e4800b1 100644
--- a/PCbuild/pythoncore.vcxproj
+++ b/PCbuild/pythoncore.vcxproj
@@ -332,7 +332,6 @@
<ClCompile Include="..\Modules\_json.c" />
<ClCompile Include="..\Modules\_localemodule.c" />
<ClCompile Include="..\Modules\_lsprof.c" />
- <ClCompile Include="..\Modules\_math.c" />
<ClCompile Include="..\Modules\_pickle.c" />
<ClCompile Include="..\Modules\_randommodule.c" />
<ClCompile Include="..\Modules\_sha3\sha3module.c" />
diff --git a/PCbuild/pythoncore.vcxproj.filters b/PCbuild/pythoncore.vcxproj.filters
index c1519760d2207..62aab5bccf9ef 100644
--- a/PCbuild/pythoncore.vcxproj.filters
+++ b/PCbuild/pythoncore.vcxproj.filters
@@ -689,9 +689,6 @@
<ClCompile Include="..\Modules\_lsprof.c">
<Filter>Modules</Filter>
</ClCompile>
- <ClCompile Include="..\Modules\_math.c">
- <Filter>Modules</Filter>
- </ClCompile>
<ClCompile Include="..\Modules\_pickle.c">
<Filter>Modules</Filter>
</ClCompile>
diff --git a/configure b/configure
index 198b0703fd6af..b72660d24c2a2 100755
--- a/configure
+++ b/configure
@@ -15092,7 +15092,7 @@ fi
LIBS_SAVE=$LIBS
LIBS="$LIBS $LIBM"
-for ac_func in acosh asinh atanh erf erfc expm1 finite gamma
+for ac_func in acosh asinh atanh erf erfc expm1 finite gamma lgamma log1p log2 tgamma
do :
as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
@@ -15101,21 +15101,13 @@ if eval test \"x\$"$as_ac_var"\" = x"yes"; then :
#define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
_ACEOF
-fi
-done
-
-for ac_func in lgamma log1p log2 tgamma
-do :
- as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
-ac_fn_c_check_func "$LINENO" "$ac_func" "$as_ac_var"
-if eval test \"x\$"$as_ac_var"\" = x"yes"; then :
- cat >>confdefs.h <<_ACEOF
-#define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
-_ACEOF
+else
+ as_fn_error $? "Python requires C99 compatible libm" "$LINENO" 5
fi
done
+LIBS=$LIBS_SAVE
# For multiprocessing module, check that sem_open
# actually works. For FreeBSD versions <= 7.2,
diff --git a/configure.ac b/configure.ac
index edda08daac117..4093938c209a0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4692,8 +4692,12 @@ fi
LIBS_SAVE=$LIBS
LIBS="$LIBS $LIBM"
-AC_CHECK_FUNCS([acosh asinh atanh erf erfc expm1 finite gamma])
-AC_CHECK_FUNCS([lgamma log1p log2 tgamma])
+AC_CHECK_FUNCS(
+ [acosh asinh atanh erf erfc expm1 finite gamma lgamma log1p log2 tgamma],
+ [],
+ [AC_MSG_ERROR([Python requires C99 compatible libm])]
+)
+LIBS=$LIBS_SAVE
# For multiprocessing module, check that sem_open
# actually works. For FreeBSD versions <= 7.2,
diff --git a/setup.py b/setup.py
index 4bef3cb52f2b2..850cc1ba41eb5 100644
--- a/setup.py
+++ b/setup.py
@@ -904,18 +904,14 @@ def detect_simple_extensions(self):
# Context Variables
self.add(Extension('_contextvars', ['_contextvarsmodule.c']))
- shared_math = 'Modules/_math.o'
-
# math library functions, e.g. sin()
self.add(Extension('math', ['mathmodule.c'],
- extra_objects=[shared_math],
- depends=['_math.h', shared_math],
+ depends=['_math.h'],
libraries=['m']))
# complex math library functions
self.add(Extension('cmath', ['cmathmodule.c'],
- extra_objects=[shared_math],
- depends=['_math.h', shared_math],
+ depends=['_math.h'],
libraries=['m']))
# time libraries: librt may be needed for clock_gettime()
More information about the Python-checkins
mailing list