Do not crash on using _slot and _offset suffixes on their own

4 files changed, 24 insertions, 0 deletions

diff --git a/Changelog.md b/Changelog.md
index aa2dce18..a957e928 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -79,6 +79,7 @@ Bugfixes:
  * Tests: Fix chain parameters to make ipc tests work with newer versions of cpp-ethereum.
  * Code Generator: Fix allocation of byte arrays (zeroed out too much memory).
  * Fix NatSpec json output for `@notice` and `@dev` tags on contract definitions.
+ * References Resolver: Do not crash on using ``_slot`` and ``_offset`` suffixes on their own.
  * References Resolver: Enforce ``storage`` as data location for mappings.
  * References Resolver: Report error instead of assertion fail when FunctionType has an undeclared type as parameter.
  * Type Checker: Disallow assignments to mappings within tuple assignments as well.
diff --git a/libsolidity/analysis/ReferencesResolver.cpp b/libsolidity/analysis/ReferencesResolver.cpp
index ba793933..5458c1b0 100644
--- a/libsolidity/analysis/ReferencesResolver.cpp
+++ b/libsolidity/analysis/ReferencesResolver.cpp
@@ -256,6 +256,11 @@ bool ReferencesResolver::visit(InlineAssembly const& _inlineAssembly)
 				string("_slot").size() :
 				string("_offset").size()
 			));
+			if (realName.empty())
+			{
+				declarationError(_identifier.location, "In variable names _slot and _offset can only be used as a suffix.");
+				return size_t(-1);
+			}
 			declarations = m_resolver.nameFromCurrentScope(realName);
 		}
 		if (declarations.size() != 1)
diff --git a/test/libsolidity/syntaxTests/inlineAssembly/storage_reference_empty_offset.sol b/test/libsolidity/syntaxTests/inlineAssembly/storage_reference_empty_offset.sol
new file mode 100644
index 00000000..ec23a263
--- /dev/null
+++ b/test/libsolidity/syntaxTests/inlineAssembly/storage_reference_empty_offset.sol
@@ -0,0 +1,9 @@
+contract C {
+    function f() public pure {
+        assembly {
+            _offset
+        }
+    }
+}
+// ----
+// DeclarationError: (75-82): In variable names _slot and _offset can only be used as a suffix.
diff --git a/test/libsolidity/syntaxTests/inlineAssembly/storage_reference_empty_slot.sol b/test/libsolidity/syntaxTests/inlineAssembly/storage_reference_empty_slot.sol
new file mode 100644
index 00000000..d493a68a
--- /dev/null
+++ b/test/libsolidity/syntaxTests/inlineAssembly/storage_reference_empty_slot.sol
@@ -0,0 +1,9 @@
+contract C {
+    function f() public pure {
+        assembly {
+            _slot
+        }
+    }
+}
+// ----
+// DeclarationError: (75-80): In variable names _slot and _offset can only be used as a suffix.