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gh-NNNN: Remove Python/dtoa.c and its init/fini plumbing
Python/dtoa.c (the 2800-line David Gay dtoa + _Py_dg_strtod) is now completely unreachable — format_float_short and _PyOS_ascii_strtod went through _Py_fmt_dtoa and _Py_wuffs_strtod in the previous two commits. Delete the file and strip the plumbing it had acquired across the rest of the tree: * Include/internal/pycore_dtoa.h: drop the _Py_dg_* declarations, _PyDtoa_Init/Fini, and _dtoa_state_INIT. Header now only declares _Py_fmt_dtoa / _Py_fmt_dtoa_free / _Py_wuffs_strtod. * Include/internal/pycore_interp_structs.h: remove `struct Bigint`, `struct _dtoa_state`, and the `dtoa` field on `PyInterpreterState`. Saves ~2.3 KB of static state per interpreter. * Include/internal/pycore_runtime_init.h: drop the `.dtoa = ...` line and the now-unused pycore_dtoa.h include. * Python/pystate.c / Python/pylifecycle.c: drop the dtoa-state fix-up in per-interpreter init and the _PyDtoa_Init / _PyDtoa_Fini calls. * Makefile.pre.in: drop Python/dtoa.o from LIBRARY_OBJS and the dedicated -fno-strict-aliasing rule that existed to work around a clang 4 miscompile of dtoa's ratio() (bpo-30104). * PCbuild/pythoncore.vcxproj{,.filters}: drop the ClCompile entry for Python/dtoa.c on Windows. Full float-formatting + strtod + C-API regression passes (1,501 tests across test_float, test_strtod, test_format, test_capi). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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‎Include/internal/pycore_dtoa.h‎

Lines changed: 10 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -11,33 +11,16 @@ extern "C" {
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#include "pycore_pymath.h" // _PY_SHORT_FLOAT_REPR
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#if defined(Py_USING_MEMORY_DEBUGGER) || _PY_SHORT_FLOAT_REPR == 0
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#define _dtoa_state_INIT(INTERP) \
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{0}
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#else
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#define _dtoa_state_INIT(INTERP) \
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{ \
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.preallocated_next = (INTERP)->dtoa.preallocated, \
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}
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#endif
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extern double _Py_dg_strtod(const char *str, char **ptr);
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extern char* _Py_dg_dtoa(double d, int mode, int ndigits,
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int *decpt, int *sign, char **rve);
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extern void _Py_dg_freedtoa(char *s);
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extern PyStatus _PyDtoa_Init(PyInterpreterState *interp);
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extern void _PyDtoa_Fini(PyInterpreterState *interp);
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// Replacements for the two David Gay entry points above. _Py_fmt_dtoa is
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// backed by Python/_fmt/ (a vendored trim of fmtlib); _Py_wuffs_strtod is
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// backed by Python/_wuffs/ (a vendored trim of Wuffs). Calling conventions
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// match _Py_dg_dtoa / _Py_dg_strtod respectively so pystrtod.c can swap them
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// in without touching call-site logic.
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// Float <-> string conversion entry points for libpython. Both replace
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// David Gay's dtoa machinery that previously lived in Python/dtoa.c:
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//
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// * _Py_fmt_dtoa is backed by a vendored trim of fmtlib ({fmt}) in
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// Python/_fmt/. Mirrors _Py_dg_dtoa's calling convention for modes
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// 0/2/3. The returned char* is PyMem_Malloc'd — pair each call with
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// _Py_fmt_dtoa_free.
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//
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// * _Py_wuffs_strtod is backed by a vendored trim of Wuffs in
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// Python/_wuffs/. Mirrors _Py_dg_strtod's calling convention.
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extern char* _Py_fmt_dtoa(double d, int mode, int ndigits,
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int *decpt, int *sign, char **rve);
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extern void _Py_fmt_dtoa_free(char *s);

‎Include/internal/pycore_interp_structs.h‎

Lines changed: 5 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -454,44 +454,11 @@ typedef struct _PyOptimizationConfig {
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bool uops_optimize_enabled;
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} _PyOptimizationConfig;
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struct
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Bigint {
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struct Bigint *next;
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int k, maxwds, sign, wds;
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uint32_t x[1];
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};
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#if defined(Py_USING_MEMORY_DEBUGGER) || _PY_SHORT_FLOAT_REPR == 0
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struct _dtoa_state {
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int _not_used;
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};
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#else // !Py_USING_MEMORY_DEBUGGER && _PY_SHORT_FLOAT_REPR != 0
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/* The size of the Bigint freelist */
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#define Bigint_Kmax 7
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/* The size of the cached powers of 5 array */
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#define Bigint_Pow5size 8
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#ifndef PRIVATE_MEM
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#define PRIVATE_MEM 2304
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#endif
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#define Bigint_PREALLOC_SIZE \
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((PRIVATE_MEM+sizeof(double)-1)/sizeof(double))
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struct _dtoa_state {
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// p5s is an array of powers of 5 of the form:
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// 5**(2**(i+2)) for 0 <= i < Bigint_Pow5size
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struct Bigint *p5s[Bigint_Pow5size];
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// XXX This should be freed during runtime fini.
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struct Bigint *freelist[Bigint_Kmax+1];
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double preallocated[Bigint_PREALLOC_SIZE];
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double *preallocated_next;
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};
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#endif // !Py_USING_MEMORY_DEBUGGER
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// `struct Bigint` and `struct _dtoa_state` used to live here to back the
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// David Gay dtoa's per-interpreter `Bigint` freelist and 2 KB pre-allocated
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// arena. With dtoa replaced by fmt + wuffs, neither is reachable — fmt uses
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// stdlib malloc via its own allocator template, and wuffs uses stack-bounded
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// state.
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struct _py_code_state {
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PyMutex mutex;
@@ -988,7 +955,6 @@ struct _is {
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struct _py_object_state object_state;
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struct _Py_unicode_state unicode;
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struct _Py_long_state long_state;
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struct _dtoa_state dtoa;
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struct _py_func_state func_state;
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struct _py_code_state code_state;
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‎Include/internal/pycore_runtime_init.h‎

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,6 @@ extern "C" {
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#include "pycore_structs.h"
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#include "pycore_ceval_state.h" // _PyEval_RUNTIME_PERF_INIT
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#include "pycore_debug_offsets.h" // _Py_DebugOffsets_INIT()
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#include "pycore_dtoa.h" // _dtoa_state_INIT()
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#include "pycore_faulthandler.h" // _faulthandler_runtime_state_INIT
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#include "pycore_floatobject.h" // _py_float_format_*
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#include "pycore_function.h"
@@ -142,7 +141,6 @@ extern PyTypeObject _PyExc_MemoryError;
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.wr_seq = QSBR_INITIAL, \
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.rd_seq = QSBR_INITIAL, \
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}, \
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.dtoa = _dtoa_state_INIT(&(INTERP)), \
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.dict_state = _dict_state_INIT, \
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.mem_free_queue = _Py_mem_free_queue_INIT(INTERP.mem_free_queue), \
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.func_state = { \

‎Makefile.pre.in‎

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Original file line numberDiff line numberDiff line change
@@ -513,7 +513,6 @@ PYTHON_OBJS= \
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Python/pystrcmp.o \
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Python/pystrtod.o \
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Python/pystrhex.o \
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Python/dtoa.o \
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Python/_fmt/fmt_dtoa.o \
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Python/_wuffs/wuffs_strtod.o \
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Python/fileutils.o \
@@ -3231,13 +3230,6 @@ regen-jit:
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.c.o:
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$(CC) -c $(PY_CORE_CFLAGS) -o $@ $<
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3234-
# bpo-30104: dtoa.c uses union to cast double to unsigned long[2]. clang 4.0
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# with -O2 or higher and strict aliasing miscompiles the ratio() function
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# causing rounding issues. Compile dtoa.c using -fno-strict-aliasing on clang.
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# https://bugs.llvm.org//show_bug.cgi?id=31928
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Python/dtoa.o: Python/dtoa.c
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$(CC) -c $(PY_CORE_CFLAGS) $(CFLAGS_ALIASING) -o $@ $<
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# Vendored {fmt} float-to-string path — see Python/_fmt/README.vendor.
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# Compiled as C++17 with exceptions and RTTI disabled so libpython doesn't
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# acquire a libstdc++ runtime dependency beyond what operator new pulls in.

‎PCbuild/pythoncore.vcxproj‎

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@@ -670,7 +670,6 @@
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<ClCompile Include="..\Python\pystrtod.c" />
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<ClCompile Include="..\Python\remote_debugging.c" />
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<ClCompile Include="..\Python\qsbr.c" />
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<ClCompile Include="..\Python\dtoa.c" />
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<ClCompile Include="..\Python\Python-ast.c" />
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<ClCompile Include="..\Python\Python-tokenize.c" />
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<ClCompile Include="..\Python\pythonrun.c" />

‎PCbuild/pythoncore.vcxproj.filters‎

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@@ -1553,9 +1553,6 @@
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<ClCompile Include="..\Python\qsbr.c">
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<Filter>Python</Filter>
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</ClCompile>
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<ClCompile Include="..\Python\dtoa.c">
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<Filter>Python</Filter>
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</ClCompile>
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<ClCompile Include="..\Python\Python-ast.c">
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<Filter>Python</Filter>
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</ClCompile>

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