Do not fold a constant if a large sequence will result.
Saves space in the presence of code like: (None,)*10000
diff --git a/Lib/test/test_peepholer.py b/Lib/test/test_peepholer.py
index 4222424..34bd99f 100644
--- a/Lib/test/test_peepholer.py
+++ b/Lib/test/test_peepholer.py
@@ -129,6 +129,10 @@
self.assert_('(2)' in asm)
self.assert_("('b')" in asm)
+ # Verify that large sequences do not result from folding
+ asm = dis_single('a="x"*1000')
+ self.assert_('(1000)' in asm)
+
def test_elim_extra_return(self):
# RETURN LOAD_CONST None RETURN --> RETURN
def f(x):
diff --git a/Python/compile.c b/Python/compile.c
index 545042f..acfbfe1 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -444,12 +444,16 @@
The consts table must still be in list form so that the
new constant can be appended.
Called with codestr pointing to the first LOAD_CONST.
- Abandons the transformation if the folding fails (i.e. 1+'a'). */
+ Abandons the transformation if the folding fails (i.e. 1+'a').
+ If the new constant is a sequence, only folds when the size
+ is below a threshold value. That keeps pyc files from
+ becoming large in the presence of code like: (None,)*1000.
+*/
static int
fold_binops_on_constants(unsigned char *codestr, PyObject *consts)
{
PyObject *newconst, *v, *w;
- int len_consts, opcode;
+ int len_consts, opcode, size;
/* Pre-conditions */
assert(PyList_CheckExact(consts));
@@ -468,8 +472,8 @@
newconst = PyNumber_Multiply(v, w);
break;
case BINARY_DIVIDE:
- /* XXX care is needed to fold this operation statically:
- the result might depend on the run-time presence of the -Qnew flag */
+ /* Cannot fold this operation statically since
+ the result can depend on the run-time presence of the -Qnew flag */
return 0;
case BINARY_TRUE_DIVIDE:
newconst = PyNumber_TrueDivide(v, w);
@@ -513,6 +517,13 @@
PyErr_Clear();
return 0;
}
+ size = PyObject_Size(newconst);
+ if (size == -1)
+ PyErr_Clear();
+ else if (size > 20) {
+ Py_DECREF(newconst);
+ return 0;
+ }
/* Append folded constant into consts table */
len_consts = PyList_GET_SIZE(consts);
@@ -733,7 +744,6 @@
LOAD_CONST c1 LOAD_CONST c2 BINOP --> LOAD_CONST binop(c1,c2) */
case BINARY_POWER:
case BINARY_MULTIPLY:
- case BINARY_DIVIDE:
case BINARY_TRUE_DIVIDE:
case BINARY_FLOOR_DIVIDE:
case BINARY_MODULO: