Fix for bug 133489: compiler leaks memory

jeremyhylton · jeremyhylton · commit 74b3bc47df99 · 2001-02-23T17:55:27.000Z
Two different but related problems:

1. PySymtable_Free() must explicitly DECREF(st-&gt;st_cur), which should
always point to the global symtable entry.  This entry is setup by the
first enter_scope() call, but there is never a corresponding
exit_scope() call.

Since each entry has a reference to scopes defined within it, the
missing DECREF caused all symtable entries to be leaked.

2. The leak here masked a separate problem with
PySymtableEntry_New().  When the requested entry was found in
st-&gt;st_symbols, the entry was returned without doing an INCREF.

And problem c) The ste_children slot was getting two copies of each
child entry, because it was populating the slot on the first and
second passes.  Now only populate on the first pass.
diff --git a/Python/compile.c b/Python/compile.c
@@ -3912,8 +3912,10 @@ jcompile(node *n, char *filename, struct compiling *base)
 		PyErr_SetString(PyExc_SystemError, "lost syntax error");
 	}
  exit:
-	if (base == NULL)
+	if (base == NULL) {
 		PySymtable_Free(sc.c_symtable);
+		sc.c_symtable = NULL;
+	}
 	com_free(&sc);
 	return co;
 }
@@ -4193,6 +4195,7 @@ PySymtable_Free(struct symtable *st)
 {
 	Py_XDECREF(st->st_symbols);
 	Py_XDECREF(st->st_stack);
+	Py_XDECREF(st->st_cur);
 	PyMem_Free((void *)st);
 }
 
@@ -4359,10 +4362,11 @@ symtable_enter_scope(struct symtable *st, char *name, int type,
 		PySymtableEntry_New(st, name, type, lineno);
 	if (strcmp(name, TOP) == 0)
 		st->st_global = st->st_cur->ste_symbols;
-	if (prev)
+	if (prev && st->st_pass == 1) {
 		if (PyList_Append(prev->ste_children, 
 				  (PyObject *)st->st_cur) < 0)
 			st->st_errors++;
+	}
 }
 
 static int
diff --git a/Python/symtable.c b/Python/symtable.c
@@ -13,8 +13,10 @@ PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
 	if (k == NULL)
 		goto fail;
 	v = PyDict_GetItem(st->st_symbols, k);
-	if (v) /* XXX could check that name, type, lineno match */
-	    return v;
+	if (v) /* XXX could check that name, type, lineno match */ {
+		Py_INCREF(v);
+		return v;
+	}
 	
 	ste = (PySymtableEntryObject *)PyObject_New(PySymtableEntryObject,
 						    &PySymtableEntry_Type);
@@ -69,7 +71,7 @@ PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
 
 	if (PyDict_SetItem(st->st_symbols, ste->ste_id, (PyObject *)ste) < 0)
 	    goto fail;
-
+	
 	return (PyObject *)ste;
  fail:
 	Py_XDECREF(ste);

Original file line number	Diff line number	Diff line change
`@@ -3912,8 +3912,10 @@ jcompile(node n, char filename, struct compiling *base)`
`3912`	`3912`	`PyErr_SetString(PyExc_SystemError, "lost syntax error");`
`3913`	`3913`	`}`
`3914`	`3914`	`exit:`
`3915`		`- if (base == NULL)`
	`3915`	`+ if (base == NULL) {`
`3916`	`3916`	`PySymtable_Free(sc.c_symtable);`
	`3917`	`+ sc.c_symtable = NULL;`
	`3918`	`+ }`
`3917`	`3919`	`com_free(&sc);`
`3918`	`3920`	`return co;`
`3919`	`3921`	`}`
`@@ -4193,6 +4195,7 @@ PySymtable_Free(struct symtable *st)`
`4193`	`4195`	`{`
`4194`	`4196`	`Py_XDECREF(st->st_symbols);`
`4195`	`4197`	`Py_XDECREF(st->st_stack);`
	`4198`	`+ Py_XDECREF(st->st_cur);`
`4196`	`4199`	`PyMem_Free((void *)st);`
`4197`	`4200`	`}`
`4198`	`4201`
`@@ -4359,10 +4362,11 @@ symtable_enter_scope(struct symtable st, char name, int type,`
`4359`	`4362`	`PySymtableEntry_New(st, name, type, lineno);`
`4360`	`4363`	`if (strcmp(name, TOP) == 0)`
`4361`	`4364`	`st->st_global = st->st_cur->ste_symbols;`
`4362`		`- if (prev)`
	`4365`	`+ if (prev && st->st_pass == 1) {`
`4363`	`4366`	`if (PyList_Append(prev->ste_children,`
`4364`	`4367`	`(PyObject *)st->st_cur) < 0)`
`4365`	`4368`	`st->st_errors++;`
	`4369`	`+ }`
`4366`	`4370`	`}`
`4367`	`4371`
`4368`	`4372`	`static int`