forked from M-Labs/nac3
core: Disallow returning of non-primitive values
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.
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@ -3,7 +3,7 @@ use crate::typecheck::typedef::TypeEnum;
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use super::type_inferencer::Inferencer;
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use super::typedef::Type;
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use nac3parser::ast::{self, Constant, Expr, ExprKind, Operator::{LShift, RShift}, Stmt, StmtKind, StrRef};
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use std::{collections::HashSet, iter::once};
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use std::{collections::HashSet, iter::once, ops::Not};
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impl<'a> Inferencer<'a> {
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fn should_have_value(&mut self, expr: &Expr<Option<Type>>) -> Result<(), HashSet<String>> {
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@ -302,6 +302,31 @@ impl<'a> Inferencer<'a> {
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if let Some(value) = value {
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self.check_expr(value, defined_identifiers)?;
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self.should_have_value(value)?;
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// Check that the return value is a non-`alloca` type, effectively only allowing primitive types.
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// This is a workaround preventing the caller from using a variable `alloca`-ed in the body, which
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// is freed when the function returns.
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if let Some(ret_ty) = value.custom {
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if [
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self.primitives.int32,
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self.primitives.int64,
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self.primitives.uint32,
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self.primitives.uint64,
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self.primitives.float,
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self.primitives.bool,
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].iter().any(|allowed_ty| self.unifier.unioned(ret_ty, *allowed_ty)).not() {
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// Explicitly allow ellipsis as a return value, as the type of the ellipsis is contextually
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// inferred and just generates an unconditional assertion
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if matches!(value.node, ExprKind::Constant { value: Constant::Ellipsis, .. }).not() {
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return Err(HashSet::from([
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format!(
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"return value of type {} must be a primitive",
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self.unifier.stringify(ret_ty),
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),
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]))
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}
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}
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}
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}
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Ok(true)
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}
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