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gh-151763: Fix OOM-0013 crash when the parser or compiler fails to allocate #151968

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Merged
pablogsal merged 2 commits into from
Jul 2, 2026
+17 −1
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gh-151763: Fix OOM-0013 crash when the parser or compiler fails to allocate #151968

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gh-151763: Fix OOM-0013 crash when the parser or compiler fails to al…
tonghuaroot Jun 23, 2026
1c1487c
Shorten the comment on the pending-exception guard
tonghuaroot Jun 23, 2026
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-06-23-12-03-55.gh-issue-151763.K7QfWG.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a potential crash in :func:`compile`, :func:`exec`, :func:`eval` and
:func:`ast.parse` when an allocation fails: the parser or compiler could
return without setting an exception.
14 changes: 13 additions & 1 deletion Parser/pegen.c
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Expand Up @@ -940,6 +940,11 @@ _PyPegen_run_parser(Parser *p)
{
void *res = _PyPegen_parse(p);
assert(p->level == 0);
if (res != NULL && PyErr_Occurred()) {

@pablogsal pablogsal Jul 2, 2026

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Do we have a way to test this? We can force the allocation failure with _testcapi.set_nomemory (there is precedent in test_exceptions.py) and assert that compile() raises MemoryError instead of crashing on the contract assert.

@pablogsal pablogsal Jul 2, 2026

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Never mind I think is fine

// Discard a result returned with an exception still pending
// (e.g. a MemoryError from a recovered-from allocation failure).
return NULL;
}
if (res == NULL) {
if ((p->flags & PyPARSE_ALLOW_INCOMPLETE_INPUT) && _is_end_of_source(p)) {
PyErr_Clear();
Expand Down Expand Up @@ -995,7 +1000,10 @@ _PyPegen_run_parser_from_file_pointer(FILE *fp, int start_rule, PyObject *filena
if (tok == NULL) {
if (PyErr_Occurred()) {
_PyTokenizer_raise_init_error(filename_ob);
return NULL;
}
else {
// The only silent tokenizer init failure is a failed allocation.
PyErr_NoMemory();
}
return NULL;
}
Expand Down Expand Up @@ -1054,6 +1062,10 @@ _PyPegen_run_parser_from_string(const char *str, int start_rule, PyObject *filen
if (PyErr_Occurred()) {
_PyTokenizer_raise_init_error(filename_ob);
}
else {
// The only silent tokenizer init failure is a failed allocation.
PyErr_NoMemory();
}
return NULL;
}
// This transfers the ownership to the tokenizer
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1 change: 1 addition & 0 deletions Python/compile.c
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Expand Up @@ -174,6 +174,7 @@ new_compiler(mod_ty mod, PyObject *filename, PyCompilerFlags *pflags,
{
compiler *c = PyMem_Calloc(1, sizeof(compiler));
if (c == NULL) {
PyErr_NoMemory();
return NULL;
}
if (compiler_setup(c, mod, filename, pflags, optimize, arena, module) < 0) {
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