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CREATE opcode: what does it really do?
Announcing the arrival of Valued Associate #679: Cesar Manara
Planned maintenance scheduled April 23, 2019 at 00:00UTC (8:00pm US/Eastern)What 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
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
asked Mar 27 at 19:41
user311703user311703
1846
add a comment |
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
asked Mar 27 at 19:41
user311703user311703
1846
add a comment |
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
asked Mar 27 at 19:41
user311703user311703
1846
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
opcode create
asked Mar 27 at 19:41
user311703user311703
1846
asked Mar 27 at 19:41
user311703user311703
1846
asked Mar 27 at 19:41
user311703user311703
1846
asked Mar 27 at 19:41
user311703user311703
1846
asked Mar 27 at 19:41
user311703user311703
1846
1846
add a comment |
add a comment |
1 Answer
1
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oldest
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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.
answered Mar 27 at 20:13
flygoingflygoing
7,755931
ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?
– user311703
Mar 27 at 20:22
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
Mar 27 at 20:23
1
CREATE executes the code passed to it, andthatcode returns the contact bytecode, yes. Just wanted to be clear on that
– flygoing
Mar 27 at 20:40
1
If you need to a call a function after it's created, then yeah, there would be aCALLright 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
Mar 27 at 20:41
1
In that case theinitcode would just return the code for your contract. The compiler basically creates adefaultconstructor that does nothing but return the actual bytecode.
– flygoing
Mar 28 at 14:22
|
show 1 more comment
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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.
answered Mar 27 at 20:13
flygoingflygoing
7,755931
ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?
– user311703
Mar 27 at 20:22
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
Mar 27 at 20:23
1
CREATE executes the code passed to it, andthatcode returns the contact bytecode, yes. Just wanted to be clear on that
– flygoing
Mar 27 at 20:40
1
If you need to a call a function after it's created, then yeah, there would be aCALLright 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
Mar 27 at 20:41
1
In that case theinitcode would just return the code for your contract. The compiler basically creates adefaultconstructor that does nothing but return the actual bytecode.
– flygoing
Mar 28 at 14:22
|
show 1 more comment
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.
answered Mar 27 at 20:13
flygoingflygoing
7,755931
ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?
– user311703
Mar 27 at 20:22
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
Mar 27 at 20:23
1
CREATE executes the code passed to it, andthatcode returns the contact bytecode, yes. Just wanted to be clear on that
– flygoing
Mar 27 at 20:40
1
If you need to a call a function after it's created, then yeah, there would be aCALLright 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
Mar 27 at 20:41
1
In that case theinitcode would just return the code for your contract. The compiler basically creates adefaultconstructor that does nothing but return the actual bytecode.
– flygoing
Mar 28 at 14:22
|
show 1 more comment
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.
answered Mar 27 at 20:13
flygoingflygoing
7,755931
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.
answered Mar 27 at 20:13
flygoingflygoing
7,755931
edited Mar 27 at 20:20
answered Mar 27 at 20:13
flygoingflygoing
7,755931
answered Mar 27 at 20:13
flygoingflygoing
7,755931
answered Mar 27 at 20:13
flygoingflygoing
7,755931
7,755931
ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?
– user311703
Mar 27 at 20:22
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
Mar 27 at 20:23
1
CREATE executes the code passed to it, andthatcode returns the contact bytecode, yes. Just wanted to be clear on that
– flygoing
Mar 27 at 20:40
1
If you need to a call a function after it's created, then yeah, there would be aCALLright 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
Mar 27 at 20:41
1
In that case theinitcode would just return the code for your contract. The compiler basically creates adefaultconstructor that does nothing but return the actual bytecode.
– flygoing
Mar 28 at 14:22
|
show 1 more comment
ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?
– user311703
Mar 27 at 20:22
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
Mar 27 at 20:23
1
CREATE executes the code passed to it, andthatcode returns the contact bytecode, yes. Just wanted to be clear on that
– flygoing
Mar 27 at 20:40
1
If you need to a call a function after it's created, then yeah, there would be aCALLright 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
Mar 27 at 20:41
1
In that case theinitcode would just return the code for your contract. The compiler basically creates adefaultconstructor that does nothing but return the actual bytecode.
– flygoing
Mar 28 at 14:22
ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?
– user311703
Mar 27 at 20:22
ah, so CREATE when creating a contract actually returns the contract bytecode, right? then after that, CALL will actually executes the contract?
– user311703
Mar 27 at 20:22
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
Mar 27 at 20:23
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
Mar 27 at 20:23
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
Mar 27 at 20:40
CREATE executes the code passed to it, and
that code returns the contact bytecode, yes. Just wanted to be clear on that– flygoing
Mar 27 at 20:40
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
Mar 27 at 20:41
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
Mar 27 at 20:41
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
Mar 28 at 14:22
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
Mar 28 at 14:22
|
show 1 more comment
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