From 87a52776905540406d45911565b8515dadba50b3 Mon Sep 17 00:00:00 2001
From: Ben Cumming <louncharf@gmail.com>
Date: Mon, 20 Nov 2017 09:49:48 +0100
Subject: [PATCH] modcc now enforces derivatives only on state variables (#392)
Derivatives should only appear on the left hand side of expressions that describe the time evolution of state variables. Without this check `modcc` segfaulted when processing a derivative expression of a non-state variable.
* Specialize the semantic analysis of `DerivativeExpression` to enforce that derivatives are only applied to state variables.
---
modcc/expression.cpp | 10 ++++++++++
modcc/expression.hpp | 2 ++
2 files changed, 12 insertions(+)
diff --git a/modcc/expression.cpp b/modcc/expression.cpp
index 2fcf79e3..dbd6ae35 100644
--- a/modcc/expression.cpp
+++ b/modcc/expression.cpp
@@ -127,6 +127,16 @@ expression_ptr DerivativeExpression::clone() const {
return make_expression<DerivativeExpression>(location_, spelling_);
}
+void DerivativeExpression::semantic(scope_ptr scp) {
+ IdentifierExpression::semantic(scp);
+ auto v = symbol_->is_variable();
+ if (!v || !v->is_state()) {
+ error( pprintf("the variable '%' must be a state variable to be differentiated",
+ yellow(spelling_), location_));
+ return;
+ }
+}
+
/*******************************************************************************
NumberExpression
********************************************************************************/
diff --git a/modcc/expression.hpp b/modcc/expression.hpp
index 84eb7d09..704f3618 100644
--- a/modcc/expression.hpp
+++ b/modcc/expression.hpp
@@ -315,6 +315,8 @@ public:
expression_ptr clone() const override;
+ void semantic(scope_ptr scp) override;
+
DerivativeExpression* is_derivative() override { return this; }
~DerivativeExpression() {}
--
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