python
diff --git a/Doc/data/stable_abi.dat b/Doc/data/stable_abi.dat
@@ -776,7 +776,6 @@ Py_SetPath
 Py_SetProgramName
 Py_SetPythonHome
 Py_SetRecursionLimit
-Py_SymtableString
 Py_UTF8Mode
 Py_VaBuildValue
 Py_XNewRef
diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
@@ -1358,3 +1358,19 @@ Removed
   AST object (``mod_ty`` type) with the public C API. The function was already
   excluded from the limited C API (:pep:`384`).
   (Contributed by Victor Stinner in :issue:`43244`.)
+
+* Remove the ``symtable.h`` header file and the undocumented functions:
+
+  * ``PyST_GetScope()``
+  * ``PySymtable_Build()``
+  * ``PySymtable_BuildObject()``
+  * ``PySymtable_Free()``
+  * ``Py_SymtableString()``
+  * ``Py_SymtableStringObject()``
+
+  The ``Py_SymtableString()`` function was part the stable ABI by mistake but
+  it could not be used, because the ``symtable.h`` header file was excluded
+  from the limited C API.
+
+  The Python :mod:`symtable` module remains available and is unchanged.
+  (Contributed by Victor Stinner in :issue:`43244`.)
diff --git a/Include/cpython/pythonrun.h b/Include/cpython/pythonrun.h
@@ -77,17 +77,6 @@ PyAPI_FUNC(const char *) _Py_SourceAsString(
     PyCompilerFlags *cf,
     PyObject **cmd_copy);
 
-PyAPI_FUNC(struct symtable *) Py_SymtableStringObject(
-    const char *str,
-    PyObject *filename,
-    int start);
-
-PyAPI_FUNC(struct symtable *) _Py_SymtableStringObjectFlags(
-    const char *str,
-    PyObject *filename,
-    int start,
-    PyCompilerFlags *flags);
-
 
 /* A function flavor is also exported by libpython. It is required when
     libpython is accessed directly rather than using header files which defines

diff --git a/Include/symtable.h → Include/internal/pycore_symtable.h b/Include/symtable.h → Include/internal/pycore_symtable.h
@@ -1,15 +1,14 @@
-#ifndef Py_LIMITED_API
-#ifndef Py_SYMTABLE_H
-#define Py_SYMTABLE_H
+#ifndef Py_INTERNAL_SYMTABLE_H
+#define Py_INTERNAL_SYMTABLE_H
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include "Python-ast.h"   /* mod_ty */
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
 
-/* XXX(ncoghlan): This is a weird mix of public names and interpreter internal
- *                names.
- */
+#include "Python-ast.h"   /* mod_ty */
 
 typedef enum _block_type { FunctionBlock, ClassBlock, ModuleBlock }
     _Py_block_ty;
@@ -68,23 +67,19 @@ typedef struct _symtable_entry {
     struct symtable *ste_table;
 } PySTEntryObject;
 
-PyAPI_DATA(PyTypeObject) PySTEntry_Type;
+extern PyTypeObject PySTEntry_Type;
 
 #define PySTEntry_Check(op) Py_IS_TYPE(op, &PySTEntry_Type)
 
-PyAPI_FUNC(int) PyST_GetScope(PySTEntryObject *, PyObject *);
+extern int _PyST_GetScope(PySTEntryObject *, PyObject *);
 
-PyAPI_FUNC(struct symtable *) PySymtable_Build(
-    mod_ty mod,
-    const char *filename,       /* decoded from the filesystem encoding */
-    PyFutureFeatures *future);
-PyAPI_FUNC(struct symtable *) PySymtable_BuildObject(
+extern struct symtable* _PySymtable_Build(
     mod_ty mod,
     PyObject *filename,
     PyFutureFeatures *future);
 PyAPI_FUNC(PySTEntryObject *) PySymtable_Lookup(struct symtable *, void *);
 
-PyAPI_FUNC(void) PySymtable_Free(struct symtable *);
+extern void _PySymtable_Free(struct symtable *);
 
 /* Flags for def-use information */
 
@@ -117,8 +112,14 @@ PyAPI_FUNC(void) PySymtable_Free(struct symtable *);
 #define GENERATOR 1
 #define GENERATOR_EXPRESSION 2
 
+// Used by symtablemodule.c
+extern struct symtable* _Py_SymtableStringObjectFlags(
+    const char *str,
+    PyObject *filename,
+    int start,
+    PyCompilerFlags *flags);
+
 #ifdef __cplusplus
 }
 #endif
-#endif /* !Py_SYMTABLE_H */
-#endif /* !Py_LIMITED_API */
+#endif /* !Py_INTERNAL_SYMTABLE_H */
diff --git a/Include/pythonrun.h b/Include/pythonrun.h
@@ -9,11 +9,6 @@ extern "C" {
 
 PyAPI_FUNC(PyObject *) Py_CompileString(const char *, const char *, int);
 
-PyAPI_FUNC(struct symtable *) Py_SymtableString(
-    const char *str,
-    const char *filename,       /* decoded from the filesystem encoding */
-    int start);
-
 PyAPI_FUNC(void) PyErr_Print(void);
 PyAPI_FUNC(void) PyErr_PrintEx(int);
 PyAPI_FUNC(void) PyErr_Display(PyObject *, PyObject *, PyObject *);

diff --git a/Makefile.pre.in b/Makefile.pre.in
@@ -1086,7 +1086,6 @@ PYTHON_HEADERS= \
 		$(srcdir)/Include/sliceobject.h \
 		$(srcdir)/Include/structmember.h \
 		$(srcdir)/Include/structseq.h \
-		$(srcdir)/Include/symtable.h \
 		$(srcdir)/Include/sysmodule.h \
 		$(srcdir)/Include/token.h \
 		$(srcdir)/Include/traceback.h \
@@ -1166,6 +1165,7 @@ PYTHON_HEADERS= \
 		$(srcdir)/Include/internal/pycore_pymem.h \
 		$(srcdir)/Include/internal/pycore_pystate.h \
 		$(srcdir)/Include/internal/pycore_runtime.h \
+		$(srcdir)/Include/internal/pycore_symtable.h \
 		$(srcdir)/Include/internal/pycore_sysmodule.h \
 		$(srcdir)/Include/internal/pycore_traceback.h \
 		$(srcdir)/Include/internal/pycore_tuple.h \

diff --git a/Misc/NEWS.d/next/C API/2021-03-17-23-53-14.bpo-43244.kfPqA_.rst b/Misc/NEWS.d/next/C API/2021-03-17-23-53-14.bpo-43244.kfPqA_.rst
@@ -0,0 +1,16 @@
+Remove the ``symtable.h`` header file and the undocumented functions:
+
+* ``PyST_GetScope()``
+* ``PySymtable_Build()``
+* ``PySymtable_BuildObject()``
+* ``PySymtable_Free()``
+* ``Py_SymtableString()``
+* ``Py_SymtableStringObject()``
+
+The ``Py_SymtableString()`` function was part the stable ABI by mistake but it
+could not be used, because the ``symtable.h`` header file was excluded from the
+limited C API.
+
+The Python :mod:`symtable` module remains available and is unchanged.
+
+Patch by Victor Stinner.
diff --git a/Modules/symtablemodule.c b/Modules/symtablemodule.c
@@ -1,8 +1,7 @@
 #include "Python.h"
 
-#include "code.h"
 #include "Python-ast.h"
-#include "symtable.h"
+#include "pycore_symtable.h"      // struct symtable
 
 #include "clinic/symtablemodule.c.h"
 /*[clinic input]
@@ -62,7 +61,7 @@ _symtable_symtable_impl(PyObject *module, PyObject *source,
     t = (PyObject *)st->st_top;
     Py_INCREF(t);
     PyMem_Free((void *)st->st_future);
-    PySymtable_Free(st);
+    _PySymtable_Free(st);
     return t;
 }
 

diff --git a/PC/python3dll.c b/PC/python3dll.c
@@ -80,7 +80,6 @@ EXPORT_FUNC(Py_SetPath)
 EXPORT_FUNC(Py_SetProgramName)
 EXPORT_FUNC(Py_SetPythonHome)
 EXPORT_FUNC(Py_SetRecursionLimit)
-EXPORT_FUNC(Py_SymtableString)
 EXPORT_FUNC(Py_VaBuildValue)
 EXPORT_FUNC(Py_XNewRef)
 EXPORT_FUNC(PyArg_Parse)

diff --git a/PCbuild/pythoncore.vcxproj b/PCbuild/pythoncore.vcxproj
@@ -208,6 +208,7 @@
     <ClInclude Include="..\Include\internal\pycore_pystate.h" />
     <ClInclude Include="..\Include\internal\pycore_runtime.h" />
     <ClInclude Include="..\Include\internal\pycore_sysmodule.h" />
+    <ClInclude Include="..\Include\internal\pycore_symtable.h" />
     <ClInclude Include="..\Include\internal\pycore_traceback.h" />
     <ClInclude Include="..\Include\internal\pycore_tuple.h" />
     <ClInclude Include="..\Include\internal\pycore_ucnhash.h" />

diff --git a/PCbuild/pythoncore.vcxproj.filters b/PCbuild/pythoncore.vcxproj.filters
@@ -585,6 +585,9 @@
     <ClInclude Include="..\Include\internal\pycore_sysmodule.h">
       <Filter>Include\internal</Filter>
     </ClInclude>
+    <ClInclude Include="..\Include\internal\pycore_symtable.h">
+      <Filter>Include\internal</Filter>
+    </ClInclude>
     <ClInclude Include="..\Include\internal\pycore_traceback.h">
       <Filter>Include\internal</Filter>
     </ClInclude>

diff --git a/Python/compile.c b/Python/compile.c
@@ -25,8 +25,8 @@
 #include "pycore_ast.h"           // _PyAST_GetDocString()
 #include "pycore_pymem.h"         // _PyMem_IsPtrFreed()
 #include "pycore_long.h"          // _PyLong_GetZero()
+#include "pycore_symtable.h"      // PySTEntryObject
 
-#include "symtable.h"             // struct symtable
 #define NEED_OPCODE_JUMP_TABLES
 #include "opcode.h"               // EXTENDED_ARG
 #include "wordcode_helpers.h"     // instrsize()
@@ -394,7 +394,7 @@ PyAST_CompileObject(mod_ty mod, PyObject *filename, PyCompilerFlags *flags,
         goto finally;
     }
 
-    c.c_st = PySymtable_BuildObject(mod, filename, c.c_future);
+    c.c_st = _PySymtable_Build(mod, filename, c.c_future);
     if (c.c_st == NULL) {
         if (!PyErr_Occurred())
             PyErr_SetString(PyExc_SystemError, "no symtable");
@@ -428,7 +428,7 @@ static void
 compiler_free(struct compiler *c)
 {
     if (c->c_st)
-        PySymtable_Free(c->c_st);
+        _PySymtable_Free(c->c_st);
     if (c->c_future)
         PyObject_Free(c->c_future);
     Py_XDECREF(c->c_filename);
@@ -729,7 +729,7 @@ compiler_set_qualname(struct compiler *c)
             mangled = _Py_Mangle(parent->u_private, u->u_name);
             if (!mangled)
                 return 0;
-            scope = PyST_GetScope(parent->u_ste, mangled);
+            scope = _PyST_GetScope(parent->u_ste, mangled);
             Py_DECREF(mangled);
             assert(scope != GLOBAL_IMPLICIT);
             if (scope == GLOBAL_EXPLICIT)
@@ -1920,10 +1920,10 @@ get_ref_type(struct compiler *c, PyObject *name)
     if (c->u->u_scope_type == COMPILER_SCOPE_CLASS &&
         _PyUnicode_EqualToASCIIString(name, "__class__"))
         return CELL;
-    scope = PyST_GetScope(c->u->u_ste, name);
+    scope = _PyST_GetScope(c->u->u_ste, name);
     if (scope == 0) {
         PyErr_Format(PyExc_SystemError,
-                     "PyST_GetScope(name=%R) failed: "
+                     "_PyST_GetScope(name=%R) failed: "
                      "unknown scope in unit %S (%R); "
                      "symbols: %R; locals: %R; globals: %R",
                      name,
@@ -3608,7 +3608,7 @@ compiler_nameop(struct compiler *c, identifier name, expr_context_ty ctx)
 
     op = 0;
     optype = OP_NAME;
-    scope = PyST_GetScope(c->u->u_ste, mangled);
+    scope = _PyST_GetScope(c->u->u_ste, mangled);
     switch (scope) {
     case FREE:
         dict = c->u->u_freevars;

diff --git a/Python/pythonrun.c b/Python/pythonrun.c
@@ -23,7 +23,6 @@
 #include "token.h"                // INDENT
 #include "errcode.h"              // E_EOF
 #include "code.h"                 // PyCodeObject
-#include "symtable.h"             // PySymtable_BuildObject()
 #include "marshal.h"              // PyMarshal_ReadLongFromFile()
 
 #ifdef MS_WINDOWS
@@ -1369,48 +1368,6 @@ _Py_SourceAsString(PyObject *cmd, const char *funcname, const char *what, PyComp
     return str;
 }
 
-struct symtable *
-Py_SymtableStringObject(const char *str, PyObject *filename, int start)
-{
-    PyCompilerFlags flags = _PyCompilerFlags_INIT;
-    return _Py_SymtableStringObjectFlags(str, filename, start, &flags);
-}
-
-struct symtable *
-_Py_SymtableStringObjectFlags(const char *str, PyObject *filename, int start, PyCompilerFlags *flags)
-{
-    struct symtable *st;
-    mod_ty mod;
-    PyArena *arena;
-
-    arena = PyArena_New();
-    if (arena == NULL)
-        return NULL;
-
-    mod = PyParser_ASTFromStringObject(str, filename, start, flags, arena);
-    if (mod == NULL) {
-        PyArena_Free(arena);
-        return NULL;
-    }
-    st = PySymtable_BuildObject(mod, filename, 0);
-    PyArena_Free(arena);
-    return st;
-}
-
-struct symtable *
-Py_SymtableString(const char *str, const char *filename_str, int start)
-{
-    PyObject *filename;
-    struct symtable *st;
-
-    filename = PyUnicode_DecodeFSDefault(filename_str);
-    if (filename == NULL)
-        return NULL;
-    st = Py_SymtableStringObject(str, filename, start);
-    Py_DECREF(filename);
-    return st;
-}
-
 #if defined(USE_STACKCHECK)
 #if defined(WIN32) && defined(_MSC_VER)