bpo-35081: Move dtoa.h header to the internal C API (GH-18489)

Move the dtoa.h header file to the internal C API as pycore_dtoa.h:
it only contains private functions (prefixed by "_Py").

The math and cmath modules must now be compiled with the
Py_BUILD_CORE macro defined.

Include/Python.h

@@ -152,7 +152,6 @@
 #include "pyctype.h"
 #include "pystrtod.h"
 #include "pystrcmp.h"
-#include "dtoa.h"
 #include "fileutils.h"
 #include "pyfpe.h"
 #include "tracemalloc.h"

Include/internal/pycore_dtoa.h

@@ -1,9 +1,15 @@
-#ifndef Py_LIMITED_API
 #ifndef PY_NO_SHORT_FLOAT_REPR
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+/* These functions are used by modules compiled as C extension like math:
+   they must be exported. */
+
 PyAPI_FUNC(double) _Py_dg_strtod(const char *str, char **ptr);
 PyAPI_FUNC(char *) _Py_dg_dtoa(double d, int mode, int ndigits,
                         int *decpt, int *sign, char **rve);
@@ -11,9 +17,7 @@ PyAPI_FUNC(void) _Py_dg_freedtoa(char *s);
 PyAPI_FUNC(double) _Py_dg_stdnan(int sign);
 PyAPI_FUNC(double) _Py_dg_infinity(int sign);
 
-
 #ifdef __cplusplus
 }
 #endif
-#endif
-#endif
+#endif   /* !PY_NO_SHORT_FLOAT_REPR */

Makefile.pre.in

@@ -981,7 +981,6 @@ PYTHON_HEADERS= \
 		$(srcdir)/Include/context.h \
 		$(srcdir)/Include/descrobject.h \
 		$(srcdir)/Include/dictobject.h \
-		$(srcdir)/Include/dtoa.h \
 		$(srcdir)/Include/dynamic_annotations.h \
 		$(srcdir)/Include/enumobject.h \
 		$(srcdir)/Include/errcode.h \
@@ -1082,6 +1081,7 @@ PYTHON_HEADERS= \
 		$(srcdir)/Include/internal/pycore_code.h \
 		$(srcdir)/Include/internal/pycore_condvar.h \
 		$(srcdir)/Include/internal/pycore_context.h \
+		$(srcdir)/Include/internal/pycore_dtoa.h \
 		$(srcdir)/Include/internal/pycore_fileutils.h \
 		$(srcdir)/Include/internal/pycore_getopt.h \
 		$(srcdir)/Include/internal/pycore_gil.h \

Misc/NEWS.d/next/C API/2020-02-12-21-24-02.bpo-35081.at7BjN.rst

@@ -0,0 +1,5 @@
+Move the ``dtoa.h`` header file to the internal C API as ``pycore_dtoa.h``:
+it only contains private functions (prefixed by ``_Py``). The :mod:`math` and
+:mod:`cmath` modules must now be compiled with the ``Py_BUILD_CORE`` macro
+defined.
+

Modules/Setup

@@ -167,8 +167,8 @@ _symtable symtablemodule.c
 # Modules that should always be present (non UNIX dependent):
 
 #array arraymodule.c	# array objects
-#cmath cmathmodule.c _math.c # -lm # complex math library functions
-#math mathmodule.c _math.c # -lm # math library functions, e.g. sin()
+#cmath cmathmodule.c _math.c -DPy_BUILD_CORE_MODULE # -lm # complex math library functions
+#math mathmodule.c _math.c -DPy_BUILD_CORE_MODULE # -lm # math library functions, e.g. sin()
 #_contextvars _contextvarsmodule.c  # Context Variables
 #_struct _struct.c	# binary structure packing/unpacking
 #_weakref _weakref.c	# basic weak reference support

Modules/cmathmodule.c

@@ -3,6 +3,7 @@
 /* much code borrowed from mathmodule.c */
 
 #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. */

Modules/mathmodule.c

@@ -53,6 +53,7 @@ raised for division by zero and mod by zero.
  */
 
 #include "Python.h"
+#include "pycore_dtoa.h"
 #include "_math.h"
 
 #include "clinic/mathmodule.c.h"

Objects/floatobject.c

@@ -4,6 +4,7 @@
    for any kind of float exception without losing portability. */
 
 #include "Python.h"
+#include "pycore_dtoa.h"
 
 #include <ctype.h>
 #include <float.h>

PCbuild/pythoncore.vcxproj

@@ -166,6 +166,7 @@
     <ClInclude Include="..\Include\internal\pycore_code.h" />
     <ClInclude Include="..\Include\internal\pycore_condvar.h" />
     <ClInclude Include="..\Include\internal\pycore_context.h" />
+    <ClInclude Include="..\Include\internal\pycore_dtoa.h" />
     <ClInclude Include="..\Include\internal\pycore_fileutils.h" />
     <ClInclude Include="..\Include\internal\pycore_getopt.h" />
     <ClInclude Include="..\Include\internal\pycore_gil.h" />
@@ -223,7 +224,6 @@
     <ClInclude Include="..\Include\pystrcmp.h" />
     <ClInclude Include="..\Include\pystrtod.h" />
     <ClInclude Include="..\Include\pystrhex.h" />
-    <ClInclude Include="..\Include\dtoa.h" />
     <ClInclude Include="..\Include\Python-ast.h" />
     <ClInclude Include="..\Include\Python.h" />
     <ClInclude Include="..\Include\pythonrun.h" />

PCbuild/pythoncore.vcxproj.filters

@@ -201,6 +201,9 @@
     <ClInclude Include="..\Include\internal\pycore_context.h">
       <Filter>Include</Filter>
     </ClInclude>
+    <ClInclude Include="..\Include\internal\pycore_dtoa.h">
+      <Filter>Include</Filter>
+    </ClInclude>
     <ClInclude Include="..\Include\internal\pycore_fileutils.h">
       <Filter>Include</Filter>
     </ClInclude>
@@ -360,9 +363,6 @@
     <ClInclude Include="..\Include\pystrhex.h">
       <Filter>Include</Filter>
     </ClInclude>
-    <ClInclude Include="..\Include\dtoa.h">
-      <Filter>Include</Filter>
-    </ClInclude>
     <ClInclude Include="..\Include\Python-ast.h">
       <Filter>Include</Filter>
     </ClInclude>

Python/dtoa.c

@@ -115,6 +115,7 @@
 /* Linking of Python's #defines to Gay's #defines starts here. */
 
 #include "Python.h"
+#include "pycore_dtoa.h"
 
 /* if PY_NO_SHORT_FLOAT_REPR is defined, then don't even try to compile
    the following code */

Python/pystrtod.c

@@ -1,6 +1,7 @@
 /* -*- Mode: C; c-file-style: "python" -*- */
 
 #include <Python.h>
+#include "pycore_dtoa.h"
 #include <locale.h>
 
 /* Case-insensitive string match used for nan and inf detection; t should be

setup.py

@@ -734,12 +734,14 @@ class PyBuildExt(build_ext):
 
         # math library functions, e.g. sin()
         self.add(Extension('math',  ['mathmodule.c'],
+                           extra_compile_args=['-DPy_BUILD_CORE_MODULE'],
                            extra_objects=[shared_math],
                            depends=['_math.h', shared_math],
                            libraries=['m']))
 
         # complex math library functions
         self.add(Extension('cmath', ['cmathmodule.c'],
+                           extra_compile_args=['-DPy_BUILD_CORE_MODULE'],
                            extra_objects=[shared_math],
                            depends=['_math.h', shared_math],
                            libraries=['m']))