gh-148973: fix segfault on mismatch between consts size and oparg in compiler (#148974)

Modules/_testinternalcapi.c

@@ -1081,13 +1081,17 @@ _testinternalcapi.compiler_codegen -> object
   compile_mode: int = 0
 
 Apply compiler code generation to an AST.
+
+Return (instruction_sequence, metadata).  metadata maps "argcount",
+"posonlyargcount", "kwonlyargcount" to ints and "consts" to the list of
+constants in LOAD_CONST index order (for use with optimize_cfg).
 [clinic start generated code]*/
 
 static PyObject *
 _testinternalcapi_compiler_codegen_impl(PyObject *module, PyObject *ast,
                                         PyObject *filename, int optimize,
                                         int compile_mode)
-/*[clinic end generated code: output=40a68f6e13951cc8 input=a0e00784f1517cd7]*/
+/*[clinic end generated code: output=40a68f6e13951cc8 input=e0c65e5c80efe30e]*/
 {
     PyCompilerFlags *flags = NULL;
     return _PyCompile_CodeGen(ast, filename, flags, optimize, compile_mode);
@@ -1103,12 +1107,15 @@ _testinternalcapi.optimize_cfg -> object
   nlocals: int
 
 Apply compiler optimizations to an instruction list.
+
+consts must be a list aligned with LOAD_CONST opargs (the "consts" entry
+from the metadata dict returned by compiler_codegen for the same unit).
 [clinic start generated code]*/
 
 static PyObject *
 _testinternalcapi_optimize_cfg_impl(PyObject *module, PyObject *instructions,
                                     PyObject *consts, int nlocals)
-/*[clinic end generated code: output=57c53c3a3dfd1df0 input=6a96d1926d58d7e5]*/
+/*[clinic end generated code: output=57c53c3a3dfd1df0 input=905c3d935e063b27]*/
 {
     return _PyCompile_OptimizeCfg(instructions, consts, nlocals);
 }

Modules/clinic/_testinternalcapi.c.h

@@ -92,7 +92,11 @@ PyDoc_STRVAR(_testinternalcapi_compiler_codegen__doc__,
 "compiler_codegen($module, /, ast, filename, optimize, compile_mode=0)\n"
 "--\n"
 "\n"
-"Apply compiler code generation to an AST.");
+"Apply compiler code generation to an AST.\n"
+"\n"
+"Return (instruction_sequence, metadata).  metadata maps \"argcount\",\n"
+"\"posonlyargcount\", \"kwonlyargcount\" to ints and \"consts\" to the list of\n"
+"constants in LOAD_CONST index order (for use with optimize_cfg).");
 
 #define _TESTINTERNALCAPI_COMPILER_CODEGEN_METHODDEF    \
     {"compiler_codegen", _PyCFunction_CAST(_testinternalcapi_compiler_codegen), METH_FASTCALL|METH_KEYWORDS, _testinternalcapi_compiler_codegen__doc__},
@@ -169,7 +173,10 @@ PyDoc_STRVAR(_testinternalcapi_optimize_cfg__doc__,
 "optimize_cfg($module, /, instructions, consts, nlocals)\n"
 "--\n"
 "\n"
-"Apply compiler optimizations to an instruction list.");
+"Apply compiler optimizations to an instruction list.\n"
+"\n"
+"consts must be a list aligned with LOAD_CONST opargs (the \"consts\" entry\n"
+"from the metadata dict returned by compiler_codegen for the same unit).");
 
 #define _TESTINTERNALCAPI_OPTIMIZE_CFG_METHODDEF    \
     {"optimize_cfg", _PyCFunction_CAST(_testinternalcapi_optimize_cfg), METH_FASTCALL|METH_KEYWORDS, _testinternalcapi_optimize_cfg__doc__},
@@ -392,4 +399,4 @@ get_next_dict_keys_version(PyObject *module, PyObject *Py_UNUSED(ignored))
 {
     return get_next_dict_keys_version_impl(module);
 }
-/*[clinic end generated code: output=fbd8b7e0cae8bac7 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=ecb5d7ac85b153fa input=a9049054013a1b77]*/