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CREATE opcode: what does it really do?



The Next CEO of Stack OverflowWhat does bytecode of blank contract do?When does a SUICIDE opcode becomes effective?Possible to create new contract via a proposal in the ethereum.org/dao framework?What are the two arguments to a RETURN opcode?Can the CALL opcode be used to create a contract?Transaction Error. Exception thrown in contract code. REVERT opcode when sending ETH to crowdsaleWhat happens in CALL when gas is set to 0?Ethereum opcode: meaning of first few instructions?callvalue opcode, for what?EVM SIGNEXTEND Opcode explanation










2















I am looking at the docs, but cannot really understand what CREATE opcode does. I can tell that CREATE does create a new smart contract from a memory chunk, pass the gas value to this new contract, then returns. But before returning, does it execute the new contract?



This confuses me because looking at the disassembly code of the smart contract bytecode, after CREATE, I cannot see any call to CALL after that, but then I still see a call to RETURNDATASIZE, which I suppose only happen after CALL. Without CALL, where it get returned data from?



Any enlighten, please?










share|improve this question


























    2















    I am looking at the docs, but cannot really understand what CREATE opcode does. I can tell that CREATE does create a new smart contract from a memory chunk, pass the gas value to this new contract, then returns. But before returning, does it execute the new contract?



    This confuses me because looking at the disassembly code of the smart contract bytecode, after CREATE, I cannot see any call to CALL after that, but then I still see a call to RETURNDATASIZE, which I suppose only happen after CALL. Without CALL, where it get returned data from?



    Any enlighten, please?










    share|improve this question
























      2












      2








      2








      I am looking at the docs, but cannot really understand what CREATE opcode does. I can tell that CREATE does create a new smart contract from a memory chunk, pass the gas value to this new contract, then returns. But before returning, does it execute the new contract?



      This confuses me because looking at the disassembly code of the smart contract bytecode, after CREATE, I cannot see any call to CALL after that, but then I still see a call to RETURNDATASIZE, which I suppose only happen after CALL. Without CALL, where it get returned data from?



      Any enlighten, please?










      share|improve this question














      I am looking at the docs, but cannot really understand what CREATE opcode does. I can tell that CREATE does create a new smart contract from a memory chunk, pass the gas value to this new contract, then returns. But before returning, does it execute the new contract?



      This confuses me because looking at the disassembly code of the smart contract bytecode, after CREATE, I cannot see any call to CALL after that, but then I still see a call to RETURNDATASIZE, which I suppose only happen after CALL. Without CALL, where it get returned data from?



      Any enlighten, please?







      opcode create






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked yesterday









      user311703user311703

      1846




      1846




















          1 Answer
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          active

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          5














          CREATE, in a way, does a built in CALL. What actually happens is that the data passed to call isn't the contract bytecode, it's the init bytecode.



          When CREATE opcode is executed, the EVM creates a call frame in the context of the new contract (e.g. address(this) is the new contracts address). This executes the data passed to CREATE as the code, which in higher level languages is basically the constructor. At the end of this init stuff, it returns the actual code of the contract that is stored in the state trie.



          The easiest way to think about it, which is also fairly accurate, is that the Solidity compiler takes all the executional code of the contract, compiles it to bytecode, and adds it as a return statement at the end of the constructor.






          share|improve this answer

























          • ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?

            – user311703
            yesterday











          • Please could you tell me what is the best way to track/trace what is really happening at bytecode level? Does Remix a good tool to do this?

            – user311703
            yesterday






          • 1





            CREATE executes the code passed to it, and that code returns the contact bytecode, yes. Just wanted to be clear on that

            – flygoing
            yesterday






          • 1





            If you need to a call a function after it's created, then yeah, there would be a CALL right after. Remix is a pretty good way to track/trace on the bytecode level, it has pretty good EVM debugging tools for stepping in/out of bytecode

            – flygoing
            yesterday






          • 1





            In that case the init code would just return the code for your contract. The compiler basically creates a default constructor that does nothing but return the actual bytecode.

            – flygoing
            13 hours ago











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          1 Answer
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          1 Answer
          1






          active

          oldest

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          active

          oldest

          votes






          active

          oldest

          votes









          5














          CREATE, in a way, does a built in CALL. What actually happens is that the data passed to call isn't the contract bytecode, it's the init bytecode.



          When CREATE opcode is executed, the EVM creates a call frame in the context of the new contract (e.g. address(this) is the new contracts address). This executes the data passed to CREATE as the code, which in higher level languages is basically the constructor. At the end of this init stuff, it returns the actual code of the contract that is stored in the state trie.



          The easiest way to think about it, which is also fairly accurate, is that the Solidity compiler takes all the executional code of the contract, compiles it to bytecode, and adds it as a return statement at the end of the constructor.






          share|improve this answer

























          • ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?

            – user311703
            yesterday











          • Please could you tell me what is the best way to track/trace what is really happening at bytecode level? Does Remix a good tool to do this?

            – user311703
            yesterday






          • 1





            CREATE executes the code passed to it, and that code returns the contact bytecode, yes. Just wanted to be clear on that

            – flygoing
            yesterday






          • 1





            If you need to a call a function after it's created, then yeah, there would be a CALL right after. Remix is a pretty good way to track/trace on the bytecode level, it has pretty good EVM debugging tools for stepping in/out of bytecode

            – flygoing
            yesterday






          • 1





            In that case the init code would just return the code for your contract. The compiler basically creates a default constructor that does nothing but return the actual bytecode.

            – flygoing
            13 hours ago















          5














          CREATE, in a way, does a built in CALL. What actually happens is that the data passed to call isn't the contract bytecode, it's the init bytecode.



          When CREATE opcode is executed, the EVM creates a call frame in the context of the new contract (e.g. address(this) is the new contracts address). This executes the data passed to CREATE as the code, which in higher level languages is basically the constructor. At the end of this init stuff, it returns the actual code of the contract that is stored in the state trie.



          The easiest way to think about it, which is also fairly accurate, is that the Solidity compiler takes all the executional code of the contract, compiles it to bytecode, and adds it as a return statement at the end of the constructor.






          share|improve this answer

























          • ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?

            – user311703
            yesterday











          • Please could you tell me what is the best way to track/trace what is really happening at bytecode level? Does Remix a good tool to do this?

            – user311703
            yesterday






          • 1





            CREATE executes the code passed to it, and that code returns the contact bytecode, yes. Just wanted to be clear on that

            – flygoing
            yesterday






          • 1





            If you need to a call a function after it's created, then yeah, there would be a CALL right after. Remix is a pretty good way to track/trace on the bytecode level, it has pretty good EVM debugging tools for stepping in/out of bytecode

            – flygoing
            yesterday






          • 1





            In that case the init code would just return the code for your contract. The compiler basically creates a default constructor that does nothing but return the actual bytecode.

            – flygoing
            13 hours ago













          5












          5








          5







          CREATE, in a way, does a built in CALL. What actually happens is that the data passed to call isn't the contract bytecode, it's the init bytecode.



          When CREATE opcode is executed, the EVM creates a call frame in the context of the new contract (e.g. address(this) is the new contracts address). This executes the data passed to CREATE as the code, which in higher level languages is basically the constructor. At the end of this init stuff, it returns the actual code of the contract that is stored in the state trie.



          The easiest way to think about it, which is also fairly accurate, is that the Solidity compiler takes all the executional code of the contract, compiles it to bytecode, and adds it as a return statement at the end of the constructor.






          share|improve this answer















          CREATE, in a way, does a built in CALL. What actually happens is that the data passed to call isn't the contract bytecode, it's the init bytecode.



          When CREATE opcode is executed, the EVM creates a call frame in the context of the new contract (e.g. address(this) is the new contracts address). This executes the data passed to CREATE as the code, which in higher level languages is basically the constructor. At the end of this init stuff, it returns the actual code of the contract that is stored in the state trie.



          The easiest way to think about it, which is also fairly accurate, is that the Solidity compiler takes all the executional code of the contract, compiles it to bytecode, and adds it as a return statement at the end of the constructor.







          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited yesterday

























          answered yesterday









          flygoingflygoing

          7,595931




          7,595931












          • ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?

            – user311703
            yesterday











          • Please could you tell me what is the best way to track/trace what is really happening at bytecode level? Does Remix a good tool to do this?

            – user311703
            yesterday






          • 1





            CREATE executes the code passed to it, and that code returns the contact bytecode, yes. Just wanted to be clear on that

            – flygoing
            yesterday






          • 1





            If you need to a call a function after it's created, then yeah, there would be a CALL right after. Remix is a pretty good way to track/trace on the bytecode level, it has pretty good EVM debugging tools for stepping in/out of bytecode

            – flygoing
            yesterday






          • 1





            In that case the init code would just return the code for your contract. The compiler basically creates a default constructor that does nothing but return the actual bytecode.

            – flygoing
            13 hours ago

















          • ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?

            – user311703
            yesterday











          • Please could you tell me what is the best way to track/trace what is really happening at bytecode level? Does Remix a good tool to do this?

            – user311703
            yesterday






          • 1





            CREATE executes the code passed to it, and that code returns the contact bytecode, yes. Just wanted to be clear on that

            – flygoing
            yesterday






          • 1





            If you need to a call a function after it's created, then yeah, there would be a CALL right after. Remix is a pretty good way to track/trace on the bytecode level, it has pretty good EVM debugging tools for stepping in/out of bytecode

            – flygoing
            yesterday






          • 1





            In that case the init code would just return the code for your contract. The compiler basically creates a default constructor that does nothing but return the actual bytecode.

            – flygoing
            13 hours ago
















          ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?

          – user311703
          yesterday





          ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?

          – user311703
          yesterday













          Please could you tell me what is the best way to track/trace what is really happening at bytecode level? Does Remix a good tool to do this?

          – user311703
          yesterday





          Please could you tell me what is the best way to track/trace what is really happening at bytecode level? Does Remix a good tool to do this?

          – user311703
          yesterday




          1




          1





          CREATE executes the code passed to it, and that code returns the contact bytecode, yes. Just wanted to be clear on that

          – flygoing
          yesterday





          CREATE executes the code passed to it, and that code returns the contact bytecode, yes. Just wanted to be clear on that

          – flygoing
          yesterday




          1




          1





          If you need to a call a function after it's created, then yeah, there would be a CALL right after. Remix is a pretty good way to track/trace on the bytecode level, it has pretty good EVM debugging tools for stepping in/out of bytecode

          – flygoing
          yesterday





          If you need to a call a function after it's created, then yeah, there would be a CALL right after. Remix is a pretty good way to track/trace on the bytecode level, it has pretty good EVM debugging tools for stepping in/out of bytecode

          – flygoing
          yesterday




          1




          1





          In that case the init code would just return the code for your contract. The compiler basically creates a default constructor that does nothing but return the actual bytecode.

          – flygoing
          13 hours ago





          In that case the init code would just return the code for your contract. The compiler basically creates a default constructor that does nothing but return the actual bytecode.

          – flygoing
          13 hours ago

















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