Fix for SF [ 734869 ] Lambda functions in list comprehensions

The compiler was reseting the list comprehension tmpname counter for each function, but the symtable was using the same counter for the entire module.  Repair by move tmpname into the symtable entry.

Bugfix candidate.

Include/symtable.h

@@ -28,7 +28,6 @@ struct symtable {
 	int st_nscopes;          /* number of scopes */
 	int st_errors;           /* number of errors */
 	char *st_private;        /* name of current class or NULL */
-	int st_tmpname;          /* temporary name counter */
 	PyFutureFeatures *st_future; /* module's future features */
 };
 
@@ -47,6 +46,7 @@ typedef struct _symtable_entry {
 				    including free refs to globals */
 	int ste_generator;       /* true if namespace is a generator */
 	int ste_opt_lineno;      /* lineno of last exec or import * */
+	int ste_tmpname;          /* temporary name counter */
 	struct symtable *ste_table;
 } PySymtableEntryObject;
 

Lib/test/output/test_grammar

@@ -60,6 +60,7 @@ classdef
 [3, 4, 5]
 [(1, 'Apple'), (1, 'Banana'), (1, 'Coconut'), (2, 'Apple'), (2, 'Banana'), (2, 'Coconut'), (3, 'Apple'), (3, 'Banana'), (3, 'Coconut'), (4, 'Apple'), (4, 'Banana'), (4, 'Coconut'), (5, 'Apple'), (5, 'Banana'), (5, 'Coconut')]
 [(1, 'Banana'), (1, 'Coconut'), (2, 'Banana'), (2, 'Coconut'), (3, 'Banana'), (3, 'Coconut'), (4, 'Banana'), (4, 'Coconut'), (5, 'Banana'), (5, 'Coconut')]
+[[1], [1, 1], [1, 2, 4], [1, 3, 9, 27], [1, 4, 16, 64, 256]]
 [False, False, False]
 [[1, 2], [3, 4], [5, 6]]
 [('Boeing', 'Airliner'), ('Boeing', 'Engine'), ('Ford', 'Engine'), ('Macdonalds', 'Cheeseburger')]

Lib/test/test_grammar.py

@@ -701,6 +701,7 @@ print [3 * x for x in nums]
 print [x for x in nums if x > 2]
 print [(i, s) for i in nums for s in strs]
 print [(i, s) for i in nums for s in [f for f in strs if "n" in f]]
+print [(lambda a:[a**i for i in range(a+1)])(j) for j in range(5)] 
 
 def test_in_func(l):
     return [None < x < 3 for x in l if x > 2]

Python/compile.c

@@ -731,6 +731,7 @@ static void symtable_global(struct symtable *, node *);
 static void symtable_import(struct symtable *, node *);
 static void symtable_assign(struct symtable *, node *, int);
 static void symtable_list_comprehension(struct symtable *, node *);
+static void symtable_list_for(struct symtable *, node *);
 
 static int symtable_update_free_vars(struct symtable *);
 static int symtable_undo_free(struct symtable *, PyObject *, PyObject *);
@@ -1602,6 +1603,8 @@ com_list_comprehension(struct compiling *c, node *n)
 {
 	/* listmaker: test list_for */
 	char tmpname[30];
+
+	REQ(n, listmaker);
 	PyOS_snprintf(tmpname, sizeof(tmpname), "_[%d]", ++c->c_tmpname);
 	com_addoparg(c, BUILD_LIST, 0);
 	com_addbyte(c, DUP_TOP); /* leave the result on the stack */
@@ -4921,7 +4924,6 @@ symtable_init()
 	st->st_cur = NULL;
 	st->st_nscopes = 0;
 	st->st_errors = 0;
-	st->st_tmpname = 0;
 	st->st_private = NULL;
 	return st;
  fail:
@@ -5123,9 +5125,6 @@ symtable_enter_scope(struct symtable *st, char *name, int type,
 	if (st->st_cur) {
 		prev = st->st_cur;
 		if (PyList_Append(st->st_stack, (PyObject *)st->st_cur) < 0) {
-			/* Py_DECREF(st->st_cur); */
-			/* I believe the previous line would lead to a
-			   double-DECREF when st is disposed - JRH */
 			st->st_errors++;
 			return;
 		}
@@ -5395,12 +5394,12 @@ symtable_node(struct symtable *st, node *n)
 		}
 		goto loop;
 	case list_iter:
+		/* only occurs when there are multiple for loops
+		   in a list comprehension */
 		n = CHILD(n, 0);
-		if (TYPE(n) == list_for) {
-			st->st_tmpname++;
-			symtable_list_comprehension(st, n);
-			st->st_tmpname--;
-		} else {
+		if (TYPE(n) == list_for)
+			symtable_list_for(st, n);
+		else {
 			REQ(n, list_if);
 			symtable_node(st, CHILD(n, 1));
 			if (NCH(n) == 3) {
@@ -5428,10 +5427,7 @@ symtable_node(struct symtable *st, node *n)
 		/* fall through */
 	case listmaker:
 		if (NCH(n) > 1 && TYPE(CHILD(n, 1)) == list_for) {
-			st->st_tmpname++;
-			symtable_list_comprehension(st, CHILD(n, 1));
-			symtable_node(st, CHILD(n, 0));
-			st->st_tmpname--;
+			symtable_list_comprehension(st, n);
 			break;
 		}
 		/* fall through */
@@ -5629,10 +5625,23 @@ symtable_global(struct symtable *st, node *n)
 static void
 symtable_list_comprehension(struct symtable *st, node *n)
 {
+	/* listmaker: test list_for */
 	char tmpname[30];
 
-	PyOS_snprintf(tmpname, sizeof(tmpname), "_[%d]", st->st_tmpname);
+	REQ(n, listmaker);
+	PyOS_snprintf(tmpname, sizeof(tmpname), "_[%d]", 
+		      ++st->st_cur->ste_tmpname);
 	symtable_add_def(st, tmpname, DEF_LOCAL);
+	symtable_list_for(st, CHILD(n, 1));
+	symtable_node(st, CHILD(n, 0));
+	--st->st_cur->ste_tmpname;
+}
+
+static void
+symtable_list_for(struct symtable *st, node *n)
+{
+	REQ(n, list_for);
+	/* list_for: for v in expr [list_iter] */
 	symtable_assign(st, CHILD(n, 1), 0);
 	symtable_node(st, CHILD(n, 3));
 	if (NCH(n) == 5)

Python/symtable.c

@@ -61,6 +61,7 @@ PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
 
 	ste->ste_optimized = 0;
 	ste->ste_opt_lineno = 0;
+	ste->ste_tmpname = 0;
 	ste->ste_lineno = lineno;
 	switch (type) {
 	case funcdef: