Vyper: Memory corruption using function calls within tuples / nested calls

Impact

When performing a function call inside a tuple or as an argument inside another function call, there is a memory corruption issue that occurs because of an incorrect pointer to the the tip of the stack.

Example code:

@internal
def _foo(a: uint256, b: uint256, c: uint256) -> (uint256, uint256, uint256, uint256, uint256):
    return 1, a, b, c, 5

@internal
def _foo2() -> uint256:
    a: uint256[10] = [6,7,8,9,10,11,12,13,15,16]
    return 4

@external
def foo() -> (uint256, uint256, uint256, uint256, uint256):
    return self._foo(2, 3, self._foo2())

Please see #2186 for further information

Patches

This problem was fixed in #2186, and released as a part of v0.2.6.