Add const ref to prevent segfaults.

Changelog.md

@@ -16,6 +16,7 @@ Bugfixes:
  * Code generator: Do not pad empty string literals with a single 32-byte zero field in the ABI coder v1.
  * SMTChecker: Fix internal compiler error when doing bitwise compound assignment with string literals.
  * SMTChecker: Fix internal error when trying to generate counterexamples with old z3.
+ * SMTChecker: Fix segmentation fault that could occur on certain SMT-enabled sources when no SMT solver was available.
  * Yul Optimizer: Fix a bug in NameSimplifier where a new name created by NameSimplifier could also be created by NameDispenser.
  * Yul Optimizer: Removed NameSimplifier from optimization steps available to users.
 

libsmtutil/CHCSmtLib2Interface.cpp

@@ -36,7 +36,7 @@ using namespace solidity::frontend;
 using namespace solidity::smtutil;
 
 CHCSmtLib2Interface::CHCSmtLib2Interface(
-	map<h256, string> _queryResponses,
+	map<h256, string> const& _queryResponses,
 	ReadCallback::Callback _smtCallback,
 	optional<unsigned> _queryTimeout
 ):

libsmtutil/CHCSmtLib2Interface.h

@@ -33,7 +33,7 @@ class CHCSmtLib2Interface: public CHCSolverInterface
 {
 public:
 	explicit CHCSmtLib2Interface(
-		std::map<util::h256, std::string> _queryResponses = {},
+		std::map<util::h256, std::string> const& _queryResponses = {},
 		frontend::ReadCallback::Callback _smtCallback = {},
 		std::optional<unsigned> _queryTimeout = {}
 	);