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bpo-34080: Fix memory leak on parsing error #8242

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bpo-34080: Fix memory leak on parsing error #8242

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bpo-34080: Fix memory leak on parsing error
vstinner Jul 11, 2018
fdf73c9
Only clear err->text in err_free()
vstinner Jul 11, 2018
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2018-07-11-11-20-12.bpo-34080.8t7PtO.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fixed a memory leak in the compiler when it raised some uncommon errors
during tokenizing.
7 changes: 4 additions & 3 deletions Parser/parsetok.c
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Expand Up @@ -246,8 +246,6 @@ parsetok(struct tok_state *tok, grammar *g, int start, perrdetail *err_ret,
else if ((ps->p_flags & CO_FUTURE_BARRY_AS_BDFL) &&
strcmp(str, "<>")) {
PyObject_FREE(str);
err_ret->text = "with Barry as BDFL, use '<>' "
"instead of '!='";
err_ret->error = E_SYNTAX;
break;
}
Expand Down Expand Up @@ -322,7 +320,10 @@ parsetok(struct tok_state *tok, grammar *g, int start, perrdetail *err_ret,
assert(tok->cur - tok->buf < INT_MAX);
err_ret->offset = (int)(tok->cur - tok->buf);
len = tok->inp - tok->buf;
err_ret->text = (char *) PyObject_MALLOC(len + 1);
/* make sure that we don't leak memory if text has been
set previously */
assert(err_ret->text == NULL);
err_ret->text = (char *) PyObject_Malloc(len + 1);
if (err_ret->text != NULL) {
if (len > 0)
strncpy(err_ret->text, tok->buf, len);
Expand Down
10 changes: 4 additions & 6 deletions Python/pythonrun.c
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Expand Up @@ -63,7 +63,7 @@ static PyObject *run_mod(mod_ty, PyObject *, PyObject *, PyObject *,
PyCompilerFlags *, PyArena *);
static PyObject *run_pyc_file(FILE *, const char *, PyObject *, PyObject *,
PyCompilerFlags *);
static void err_input(perrdetail *);
static void err_input(const perrdetail *);
static void err_free(perrdetail *);
static int PyRun_InteractiveOneObjectEx(FILE *, PyObject *, PyCompilerFlags *);

Expand Down Expand Up @@ -1324,12 +1324,14 @@ static void
err_free(perrdetail *err)
{
Py_CLEAR(err->filename);
PyObject_Free(err->text);
err->text = NULL;
}

/* Set the error appropriate to the given input error code (see errcode.h) */

static void
err_input(perrdetail *err)
err_input(const perrdetail *err)
{
PyObject *v, *w, *errtype, *errtext;
PyObject *msg_obj = NULL;
Expand Down Expand Up @@ -1445,10 +1447,6 @@ err_input(perrdetail *err)
Py_XDECREF(w);
cleanup:
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goto cleanup is used even in branches when msg_obj is always NULL. Either replace them with return, or merge #8222.

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I don't see anything wrong with calling Py_XDECREF(msg_obj) when msg_obj is NULL. It's a common try/finally-like pattern applied to the C language. Moreover, I wrote this PR to fix a real memory leak, not to cleanup the code. Don't hesitate to propose a new PR once the memory leak is fixed, if you want to clean up the code further. I prefer to write the shortest PR to be able to backport it to all branches.

Py_XDECREF(msg_obj);
if (err->text != NULL) {
PyObject_FREE(err->text);
err->text = NULL;
}
}


Expand Down