Documents library view functions and adds unit test.

2 files changed, 28 insertions, 1 deletions

diff --git a/docs/contracts.rst b/docs/contracts.rst
index faef3fc2..e4a81684 100644
--- a/docs/contracts.rst
+++ b/docs/contracts.rst
@@ -485,7 +485,9 @@ Functions can be declared ``view`` in which case they promise not to modify the
 .. note::
   If the compiler's EVM target is Byzantium or newer (default) the opcode
   ``STATICCALL`` is used for ``view`` functions which enforces the state
-  to stay unmodified as part of the EVM execution.
+  to stay unmodified as part of the EVM execution. For library ``view`` functions
+  ``DELEGATECALL`` is used. Since they are executed in the context of the calling
+  contract, the static checker is extended to the library.
 
 The following statements are considered modifying the state:
 
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index f65c8b27..7a496e64 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -4519,6 +4519,31 @@ BOOST_AUTO_TEST_CASE(library_call_protection)
 	ABI_CHECK(callContractFunction("pu()"), encodeArgs(2));
 }
 
+
+BOOST_AUTO_TEST_CASE(library_staticcall_delegatecall)
+{
+	char const* sourceCode = R"(
+		 library Lib {
+			 function x() public view returns (uint) {
+				 return 1;
+			 }
+		 }
+		 contract Test {
+			 uint t;
+			 function f() public returns (uint) {
+				 t = 2;
+				 return this.g();
+			 }
+			 function g() public view returns (uint) {
+				 return Lib.x();
+			 }
+		 }
+	)";
+	compileAndRun(sourceCode, 0, "Lib");
+	compileAndRun(sourceCode, 0, "Test", bytes(), map<string, Address>{{"Lib", m_contractAddress}});
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(1));
+}
+
 BOOST_AUTO_TEST_CASE(store_bytes)
 {
 	// this test just checks that the copy loop does not mess up the stack