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-rw-r--r--libsolidity/codegen/ExpressionCompiler.cpp17
1 files changed, 13 insertions, 4 deletions
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index 96ca4296..26acd8a4 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -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;