8000 bpo-45548: Remove _math.c workarounds for pre-C99 libm (GH-29179) · python/cpython@fa26245 · GitHub
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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@enthought.com> Co-authored-by: Brett Cannon <brett@python.org> Signed-off-by: Christian Heimes <christian@python.org>
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‎Makefile.pre.in

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@@ -611,10 +611,6 @@ pybuilddir.txt: $(BUILDPYTHON)
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exit 1 ; \
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fi
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# This is shared by the math and cmath modules
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Modules/_math.o: Modules/_math.c Modules/_math.h
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$(CC) -c $(CCSHARED) $(PY_CORE_CFLAGS) -o $@ $<
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# blake2s is auto-generated from blake2b
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$(srcdir)/Modules/_blake2/blake2s_impl.c: $(srcdir)/Modules/_blake2/blake2b_impl.c $(srcdir)/Modules/_blake2/blake2b2s.py
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$(PYTHON_FOR_REGEN) $(srcdir)/Modules/_blake2/blake2b2s.py
@@ -625,7 +621,7 @@ $(srcdir)/Modules/_blake2/blake2s_impl.c: $(srcdir)/Modules/_blake2/blake2b_impl
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# -s, --silent or --quiet is always the first char.
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# Under BSD make, MAKEFLAGS might be " -s -v x=y".
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# Ignore macros passed by GNU make, passed after --
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sharedmods: $(BUILDPYTHON) pybuilddir.txt Modules/_math.o
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sharedmods: $(BUILDPYTHON) pybuilddir.txt
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@case "`echo X $$MAKEFLAGS | sed 's/^X //;s/ -- .*//'`" in \
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*\ -s*|s*) quiet="-q";; \
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*) quiet="";; \

‎Misc/NEWS.d/next/Build/2021-10-24-21-49-49.bpo-45548.UWx0UC.rst

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The :mod:`math` and :mod:`cmath` implementation now require a C99 compatible
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``libm`` and no longer ship with workarounds for missing acosh, asinh, atanh,
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expm1, and log1p functions.

‎Modules/Setup

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@@ -171,8 +171,8 @@ time timemodule.c
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#array arraymodule.c
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#audioop audioop.c
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#binascii binascii.c
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#cmath cmathmodule.c _math.c # -lm
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#math mathmodule.c _math.c # -lm
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#cmath cmathmodule.c # -lm
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#math mathmodule.c # -lm
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#pyexpat -I$(srcdir)/Modules/expat expat/xmlparse.c expat/xmlrole.c expat/xmltok.c pyexpat.c
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#unicodedata unicodedata.c
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‎Modules/_math.c

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This file was deleted.

‎Modules/_math.h

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Original file line numberDiff line numberDiff line change
@@ -1,41 +1,24 @@
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#ifdef HAVE_ACOSH
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# define m_acosh acosh
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#else
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/* if the system doesn't have acosh, use the substitute
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function defined in Modules/_math.c. */
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double _Py_acosh(double x);
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# define m_acosh _Py_acosh
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#endif
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/* log1p(x) = log(1+x). The log1p function is designed to avoid the
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significant loss of precision that arises from direct evaluation when x is
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small. Use the substitute from _math.h on all platforms: it includes
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workarounds for buggy handling of zeros.
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*/
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10-
#ifdef HAVE_ASINH
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# define m_asinh asinh
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#else
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/* if the system doesn't have asinh, use the substitute
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function defined in Modules/_math.c. */
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double _Py_asinh(double x);
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# define m_asinh _Py_asinh
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#endif
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static double
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_Py_log1p(double x)
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{
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/* Some platforms supply a log1p function but don't respect the sign of
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zero: log1p(-0.0) gives 0.0 instead of the correct result of -0.0.
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#ifdef HAVE_ATANH
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# define m_atanh atanh
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#else
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/* if the system doesn't have atanh, use the substitute
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function defined in Modules/_math.c. */
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double _Py_atanh(double x);
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#define m_atanh _Py_atanh
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#endif
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To save fiddling with configure tests and platform checks, we handle the
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special case of zero input directly on all platforms.
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*/
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if (x == 0.0) {
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return x;
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}
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else {
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return log1p(x);
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}
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}
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#ifdef HAVE_EXPM1
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# define m_expm1 expm1
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#else
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/* if the system doesn't have expm1, use the substitute
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function defined in Modules/_math.c. */
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double _Py_expm1(double x);
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#define m_expm1 _Py_expm1
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#endif
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double _Py_log1p(double x);
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/* Use the substitute from _math.c on all platforms:
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it includes workarounds for buggy handling of zeros. */
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#define m_log1p _Py_log1p

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