pythongh-125268: Use static string for "1e309" in AST (python#125272)

When formatting the AST as a string, infinite values are replaced by 1e309, which evaluates to infinity. The initialization of this string replacement was not thread-safe in the free threading build.
colesbury · Oct 10, 2024 · 427dcf2 · 427dcf2
1 parent bb594e8
commit 427dcf2
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Showing 8 changed files with 11 additions and 32 deletions.
diff --git a/Include/internal/pycore_global_objects.h b/Include/internal/pycore_global_objects.h
@@ -66,9 +66,6 @@ struct _Py_static_objects {
 struct _Py_interp_cached_objects {
  PyObject *interned_strings;
 
- /* AST */
- PyObject *str_replace_inf;
-
  /* object.__reduce__ */
  PyObject *objreduce;
  PyObject *type_slots_pname;

diff --git a/Include/internal/pycore_global_objects_fini_generated.h b/Include/internal/pycore_global_objects_fini_generated.h
diff --git a/Include/internal/pycore_global_strings.h b/Include/internal/pycore_global_strings.h
@@ -48,6 +48,7 @@ struct _Py_global_strings {
  STRUCT_FOR_STR(json_decoder, "json.decoder")
  STRUCT_FOR_STR(kwdefaults, ".kwdefaults")
  STRUCT_FOR_STR(list_err, "list index out of range")
+ STRUCT_FOR_STR(str_replace_inf, "1e309")
  STRUCT_FOR_STR(type_params, ".type_params")
  STRUCT_FOR_STR(utf_8, "utf-8")
  } literals;

diff --git a/Include/internal/pycore_runtime_init_generated.h b/Include/internal/pycore_runtime_init_generated.h
diff --git a/Include/internal/pycore_unicodeobject_generated.h b/Include/internal/pycore_unicodeobject_generated.h
diff --git a/Parser/asdl_c.py b/Parser/asdl_c.py
@@ -2242,8 +2242,6 @@ def generate_ast_fini(module_state, f):
  for s in module_state:
  f.write(" Py_CLEAR(state->" + s + ');\n')
  f.write(textwrap.dedent("""
- Py_CLEAR(_Py_INTERP_CACHED_OBJECT(interp, str_replace_inf));
-
  state->finalized = 1;
  state->once = (_PyOnceFlag){0};
  }

diff --git a/Python/Python-ast.c b/Python/Python-ast.c
diff --git a/Python/ast_unparse.c b/Python/ast_unparse.c
@@ -2,7 +2,6 @@
 #include "pycore_ast.h" // expr_ty
 #include "pycore_pystate.h" // _PyInterpreterState_GET()
 #include "pycore_runtime.h" // _Py_ID()
-#include <float.h> // DBL_MAX_10_EXP
 #include <stdbool.h>
 
 /* This limited unparser is used to convert annotations back to strings
@@ -13,10 +12,6 @@
 _Py_DECLARE_STR(dbl_open_br, "{{");
 _Py_DECLARE_STR(dbl_close_br, "}}");
 
-/* We would statically initialize this if doing so were simple enough. */
-#define _str_replace_inf(interp) \
- _Py_INTERP_CACHED_OBJECT(interp, str_replace_inf)
-
 /* Forward declarations for recursion via helper functions. */
 static PyObject *
 expr_as_unicode(expr_ty e, int level);
@@ -78,13 +73,13 @@ append_repr(_PyUnicodeWriter *writer, PyObject *obj)
  }
 
  if ((PyFloat_CheckExact(obj) && isinf(PyFloat_AS_DOUBLE(obj))) ||
- PyComplex_CheckExact(obj))
+  PyComplex_CheckExact(obj))
  {
- PyInterpreterState *interp = _PyInterpreterState_GET();
+ _Py_DECLARE_STR(str_replace_inf, "1e309"); // evaluates to inf
  PyObject *new_repr = PyUnicode_Replace(
  repr,
  &_Py_ID(inf),
- _str_replace_inf(interp),
+ &_Py_STR(str_replace_inf),
  -1
  );
  Py_DECREF(repr);
@@ -918,30 +913,14 @@ append_ast_expr(_PyUnicodeWriter *writer, expr_ty e, int level)
  return -1;
 }
 
-static int
-maybe_init_static_strings(void)
-{
- PyInterpreterState *interp = _PyInterpreterState_GET();
- if (_str_replace_inf(interp) == NULL) {
- PyObject *tmp = PyUnicode_FromFormat("1e%d", 1 + DBL_MAX_10_EXP);
- if (tmp == NULL) {
- return -1;
- }
- _str_replace_inf(interp) = tmp;
- }
- return 0;
-}
-
 static PyObject *
 expr_as_unicode(expr_ty e, int level)
 {
  _PyUnicodeWriter writer;
  _PyUnicodeWriter_Init(&writer);
  writer.min_length = 256;
  writer.overallocate = 1;
- if (-1 == maybe_init_static_strings() ||
- -1 == append_ast_expr(&writer, e, level))
- {
+ if (-1 == append_ast_expr(&writer, e, level)) {
  _PyUnicodeWriter_Dealloc(&writer);
  return NULL;
  }