#1920: when considering a block starting by "while 0", the compiler optimized the
whole construct away, even when an 'else' clause is present::
while 0:
print("no")
else:
print("yes")
did not generate any code at all.
Now the compiler emits the 'else' block, like it already does for 'if' statements.
Will backport.
diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index 4352275..d4bcfda 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -572,6 +572,15 @@
while 0: pass
else: pass
+ # Issue1920: "while 0" is optimized away,
+ # ensure that the "else" clause is still present.
+ x = 0
+ while 0:
+ x = 1
+ else:
+ x = 2
+ self.assertEquals(x, 2)
+
def testFor(self):
# 'for' exprlist 'in' exprlist ':' suite ['else' ':' suite]
for i in 1, 2, 3: pass
diff --git a/Python/compile.c b/Python/compile.c
index c77091e..aee7bda 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -1598,8 +1598,11 @@
basicblock *loop, *orelse, *end, *anchor = NULL;
int constant = expr_constant(s->v.While.test);
- if (constant == 0)
+ if (constant == 0) {
+ if (s->v.While.orelse)
+ VISIT_SEQ(c, stmt, s->v.While.orelse);
return 1;
+ }
loop = compiler_new_block(c);
end = compiler_new_block(c);
if (constant == -1) {