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Merge pull request #5184 from ethereum/viewFunctionDocs

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Library view functions
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chriseth 2018-10-10 15:21:40 +02:00 committed by GitHub
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2 changed files with 30 additions and 1 deletions
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6
docs/contracts.rst
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@ -485,7 +485,11 @@ 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, because there is no combined ``DELEGATECALL`` and ``STATICCALL``.
This means library ``view`` functions do not have run-time checks that prevent state
modifications. This should not impact security negatively because library code is
usually known at compile-time and the static checker performs compile-time checks.
The following statements are considered modifying the state:

25
test/libsolidity/SolidityEndToEndTest.cpp
View File

@ -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