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Merge pull request #1104 from ethereum/fixmemcosts

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Fix memory resize costs during call
This commit is contained in:
chriseth 2016-09-17 12:30:41 +02:00 committed by GitHub
commit 212e016091
3 changed files with 42 additions and 4 deletions
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2
Changelog.md
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@ -2,6 +2,8 @@
* Code Generator: Fix library functions being called from payable functions.
* Type Checker: Fixed a crash about invalid array types.
* Code Generator: Fixed a call gas bug that became visible after
version 0.4.0 for calls where the output is larger than the input.
### 0.4.1 (2016-09-09)

17
libsolidity/codegen/ExpressionCompiler.cpp
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@ -1476,6 +1476,18 @@ void ExpressionCompiler::appendExternalFunctionCall(
utils().storeFreeMemoryPointer();
}
// Touch the end of the output area so that we do not pay for memory resize during the call
// (which we would have to subtract from the gas left)
// We could also just use MLOAD; POP right before the gas calculation, but the optimizer
// would remove that, so we use MSTORE here.
if (!_functionType.gasSet() && retSize > 0)
{
m_context << u256(0);
utils().fetchFreeMemoryPointer();
// This touches too much, but that way we save some rounding arithmetics
m_context << u256(retSize) << Instruction::ADD << Instruction::MSTORE;
}
// Copy function identifier to memory.
utils().fetchFreeMemoryPointer();
if (!_functionType.isBareCall() || manualFunctionId)
@ -1551,10 +1563,7 @@ void ExpressionCompiler::appendExternalFunctionCall(
gasNeededByCaller += eth::GasCosts::callValueTransferGas;
if (!isCallCode && !isDelegateCall && !existenceChecked)
gasNeededByCaller += eth::GasCosts::callNewAccountGas; // we never know
m_context <<
gasNeededByCaller <<
Instruction::GAS <<
Instruction::SUB;
m_context << gasNeededByCaller << Instruction::GAS << Instruction::SUB;
}
if (isDelegateCall)
m_context << Instruction::DELEGATECALL;

27
test/libsolidity/SolidityEndToEndTest.cpp
View File

@ -7203,6 +7203,33 @@ BOOST_AUTO_TEST_CASE(no_nonpayable_circumvention_by_modifier)
BOOST_CHECK_EQUAL(balanceAt(m_contractAddress), 0);
}
BOOST_AUTO_TEST_CASE(mem_resize_is_not_paid_at_call)
{
// This tests that memory resize for return values is not paid during the call, which would
// make the gas calculation overly complex. We access the end of the output area before
// the call is made.
// Tests that this also survives the optimizer.
char const* sourceCode = R"(
contract C {
function f() returns (uint[200]) {}
}
contract D {
function f(C c) returns (uint) { c.f(); return 7; }
}
)";
compileAndRun(sourceCode, 0, "C");
u160 cAddr = m_contractAddress;
compileAndRun(sourceCode, 0, "D");
BOOST_CHECK(callContractFunction("f(address)", cAddr) == encodeArgs(u256(7)));
m_optimize = true;
compileAndRun(sourceCode, 0, "C");
u160 cAddrOpt = m_contractAddress;
compileAndRun(sourceCode, 0, "D");
BOOST_CHECK(callContractFunction("f(address)", cAddrOpt) == encodeArgs(u256(7)));
}
BOOST_AUTO_TEST_SUITE_END()