M-Labs/nac3
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core: Disallow returning of non-primitive values

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Non-primitive values are represented by an `alloca`-ed value in the
function body, and when the pointer is returned from the function, the
`alloca`-ed object is deallocated on the stack.

Related to #54.
This commit is contained in:
David Mak 2024-01-29 12:49:24 +08:00
parent e328e44c9a
commit b3736c3e99
1 changed files with 26 additions and 1 deletions
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27
nac3core/src/typecheck/function_check.rs
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@ -3,7 +3,7 @@ use crate::typecheck::typedef::TypeEnum;
use super::type_inferencer::Inferencer;
use super::typedef::Type;
use nac3parser::ast::{self, Constant, Expr, ExprKind, Operator::{LShift, RShift}, Stmt, StmtKind, StrRef};
use std::{collections::HashSet, iter::once};
use std::{collections::HashSet, iter::once, ops::Not};
impl<'a> Inferencer<'a> {
fn should_have_value(&mut self, expr: &Expr<Option<Type>>) -> Result<(), HashSet<String>> {
@ -302,6 +302,31 @@ impl<'a> Inferencer<'a> {
if let Some(value) = value {
self.check_expr(value, defined_identifiers)?;
self.should_have_value(value)?;
// Check that the return value is a non-`alloca` type, effectively only allowing primitive types.
// This is a workaround preventing the caller from using a variable `alloca`-ed in the body, which
// is freed when the function returns.
if let Some(ret_ty) = value.custom {
if [
self.primitives.int32,
self.primitives.int64,
self.primitives.uint32,
self.primitives.uint64,
self.primitives.float,
self.primitives.bool,
].iter().any(|allowed_ty| self.unifier.unioned(ret_ty, *allowed_ty)).not() {
// Explicitly allow ellipsis as a return value, as the type of the ellipsis is contextually
// inferred and just generates an unconditional assertion
if matches!(value.node, ExprKind::Constant { value: Constant::Ellipsis, .. }).not() {
return Err(HashSet::from([
format!(
"return value of type {} must be a primitive",
self.unifier.stringify(ret_ty),
),
]))
}
}
}
}
Ok(true)
}