如何通过solc编译solidity编写的以太坊智能合约

solc：solidity 编译器

solidity编写的以太坊智能合约可以通过命令行编译工具solc进行编译，成为以太坊虚拟机中的代码。 solc编译完成后，最终部署到链上，形成我们看到的各种智能合约。

作为solidity命令行编译工具，我们来看看官网是怎么说solc的。

solc的安装很简单：

npm install -g solc
//或者
npm install -g solc-cli
//或者
sudo apt-get install solc

看看安装完成后，solc --help，solc --help命令显示了所有的solc命令选项。 编译器可以生成各种输出，比如最终的二进制合约文件，语法树的组装，或者预估的gas成本等。solc --bin sourceFile.sol，可以编译输出一个名为sourceFile.sol的智能合约文件. 如果你想要 solc 的一些更丰富的输出变量，你可以使用 solc -o outputDirectory --bin --ast --asm sourceFile.sol。

您可以在部署以太坊智能合约之前使用 solc --optimize --bin sourceFile.sol 进行优化。 默认情况下，solc编译器会帮你优化200次。 也可以设置--runs=1，这样会以最小化的方式编译。 如果您想要多次交易并且不关心成本，那么您可以将其设置为您想要的次数:)。

命令行编译器会自动读取需要导入的文件，也可以使用prefix=path指定路径，例如：

solc github.com/ethereum/dapp-bin/=/usr/local/lib/dapp-bin/=/usr/local/lib/fallback file.sol

这样，编译器就会从指定目录github.com/ethereum/dapp-bin/下的/usr/local/lib/dapp-bin/目录开始搜索。 如果找不到该文件，它将查看 /usr/local/lib/ fallback。 Solc 只会读取你指定的两个路径，所以像 import "/etc/passwd"; 它必须通过 /= 重新映射才能工作。 如果有多个匹配以太坊api，则选择公共前缀最长的匹配。

出于安全原因，编译器限制了它可以访问的目录。 拒绝在命令行上指定的源文件（及其子目录）的路径以及在命令行上指定的路径以外的所有其他内容。 --allow-paths /sample/path, /another/sample/path 切换。

如果使用智能合约，您会注意到字节码包含 __LibraryName______ 的子字符串。 您可以将 solc 用作链接器，这意味着它将在这些点为您插入库地址。

您可以通过在命令中添加 libraries --libraries "Math:0x12345678901234567890 Heap:0xabcdef0123456" 来提供每个库的地址，或者使用文件中的描述字符串（每行一个库）并使用 --libraries fileName solc 运行。

如果使用选项 --link 调用 Solc以太坊api，所有输入文件都被解释为未链接的二进制文件（十六进制编码），采用上面给出的 __LibraryName____ 格式，链接到适当的地址（如果从 stdin 输入读取，它被写入 stdout） . 在这种情况下，除了库之外的所有选项都将被忽略（包括 -o）。

如果使用 --standard-json 调用 SOLC，它将采用标准 JSON 输入（如下所述）并返回 JSON 输出。

solc编译器输入输出JSON描述

这些 JSON 格式通过编译器 API 使用，可通过 SOLC 使用。 出于向后兼容的目的，内容都是可修改的，有些对象是可选的（如前所述）。

编译器的 API 接受 JSON 格式的输入，并以 JSON 格式输出编译结果。

请注意，不允许发表评论。 以下例子中的注解在官网都有标注，方便学习者更好的理解。

{
  // Required: Source code language, such as "Solidity", "serpent", "lll", "assembly", etc.
  language: "Solidity",
  // Required
  sources:
  {
    // The keys here are the "global" names of the source files,
    // imports can use other files via remappings (see below).
    "myFile.sol":
    {
      // Optional: keccak256 hash of the source file
      // It is used to verify the retrieved content if imported via URLs.
      "keccak256": "0x123...",
      // Required (unless "content" is used, see below): URL(s) to the source file.
      // URL(s) should be imported in this order and the result checked against the
      // keccak256 hash (if available). If the hash doesn't match or none of the
      // URL(s) result in success, an error should be raised.
      "urls":

      [
        "bzzr://56ab...",
        "ipfs://Qma...",
        "file:///tmp/path/to/file.sol"
      ]
    },
    "mortal":
    {
      // Optional: keccak256 hash of the source file
      "keccak256": "0x234...",
      // Required (unless "urls" is used): literal contents of the source file
      "content": "contract mortal is owned { function kill() { if (msg.sender == owner) selfdestruct(owner); } }"
    }
  },
  // Optional
  settings:
  {
    // Optional: Sorted list of remappings
    remappings: [ ":g/dir" ],
    // Optional: Optimizer settings
    optimizer: {
      // disabled by default
      enabled: true,
      // Optimize for how many times you intend to run the code.
      // Lower values will optimize more for initial deployment cost, higher values will optimize more for high-frequency usage.
      runs: 200
    },
    evmVersion: "byzantium", // Version of the EVM to compile for. Affects type checking and code generation. Can be homestead, tangerineWhistle, spuriousDragon, byzantium or constantinople
    // Metadata settings (optional)
    metadata: {
      // Use only literal content and not URLs (false by default)
      useLiteralContent: true
    },
    // Addresses of the libraries. If not all libraries are given here, it can result in unlinked objects whose output data is different.
    libraries: {
      // The top level key is the the name of the source file where the library is used.
      // If remappings are used, this source file should match the global path after remappings were applied.
      // If this key is an empty string, that refers to a global level.
      "myFile.sol": {

        "MyLib": "0x123123..."
      }
    }
    // The following can be used to select desired outputs.
    // If this field is omitted, then the compiler loads and does type checking, but will not generate any outputs apart from errors.
    // The first level key is the file name and the second is the contract name, where empty contract name refers to the file itself,
    // while the star refers to all of the contracts.
    //
    // The available output types are as follows:
    //   abi - ABI
    //   ast - AST of all source files
    //   legacyAST - legacy AST of all source files
    //   devdoc - Developer documentation (natspec)
    //   userdoc - User documentation (natspec)
    //   metadata - Metadata
    //   ir - New assembly format before desugaring
    //   evm.assembly - New assembly format after desugaring
    //   evm.legacyAssembly - Old-style assembly format in JSON
    //   evm.bytecode.object - Bytecode object
    //   evm.bytecode.opcodes - Opcodes list
    //   evm.bytecode.sourceMap - Source mapping (useful for debugging)
    //   evm.bytecode.linkReferences - Link references (if unlinked object)
    //   evm.deployedBytecode* - Deployed bytecode (has the same options as evm.bytecode)
    //   evm.methodIdentifiers - The list of function hashes
    //   evm.gasEstimates - Function gas estimates
    //   ewasm.wast - eWASM S-expressions format (not supported atm)
    //   ewasm.wasm - eWASM binary format (not supported atm)
    //
    // Note that using a using `evm`, `evm.bytecode`, `ewasm`, etc. will select every
    // target part of that output. Additionally, `*` can be used as a wildcard to request everything.
    //
    outputSelection: {
      // Enable the metadata and bytecode outputs of every single contract.
      "*": {
        "*": [ "metadata", "evm.bytecode" ]
      },
      // Enable the abi and opcodes output of MyContract defined in file def.
      "def": {
        "MyContract": [ "abi", "evm.bytecode.opcodes" ]

      },
      // Enable the source map output of every single contract.
      "*": {
        "*": [ "evm.bytecode.sourceMap" ]
      },
      // Enable the legacy AST output of every single file.
      "*": {
        "": [ "legacyAST" ]
      }
    }
  }
}

{
  // Optional: not present if no errors/warnings were encountered
  errors: [
    {
      // Optional: Location within the source file.
      sourceLocation: {
        file: "sourceFile.sol",
        start: 0,
        end: 100
      ],
      // Mandatory: Error type, such as "TypeError", "InternalCompilerError", "Exception", etc.
      // See below for complete list of types.
      type: "TypeError",
      // Mandatory: Component where the error originated, such as "general", "ewasm", etc.
      component: "general",
      // Mandatory ("error" or "warning")
      severity: "error",
      // Mandatory
      message: "Invalid keyword"
      // Optional: the message formatted with source location
      formattedMessage: "sourceFile.sol:100: Invalid keyword"
    }
  ],
  // This contains the file-level outputs. In can be limited/filtered by the outputSelection settings.
  sources: {
    "sourceFile.sol": {
      // Identifier (used in source maps)

      id: 1,
      // The AST object
      ast: {},
      // The legacy AST object
      legacyAST: {}
    }
  },
  // This contains the contract-level outputs. It can be limited/filtered by the outputSelection settings.
  contracts: {
    "sourceFile.sol": {
      // If the language used has no contract names, this field should equal to an empty string.
      "ContractName": {
        // The Ethereum Contract ABI. If empty, it is represented as an empty array.
        // See https://github.com/ethereum/wiki/wiki/Ethereum-Contract-ABI
        abi: [],
        // See the Metadata Output documentation (serialised JSON string)
        metadata: "{...}",
        // User documentation (natspec)
        userdoc: {},
        // Developer documentation (natspec)
        devdoc: {},
        // Intermediate representation (string)
        ir: "",
        // EVM-related outputs
        evm: {
          // Assembly (string)
          assembly: "",
          // Old-style assembly (object)
          legacyAssembly: {},
          // Bytecode and related details.
          bytecode: {
            // The bytecode as a hex string.
            object: "00fe",
            // Opcodes list (string)
            opcodes: "",
            // The source mapping as a string. See the source mapping definition.
            sourceMap: "",
            // If given, this is an unlinked object.
            linkReferences: {

              "libraryFile.sol": {
                // Byte offsets into the bytecode. Linking replaces the 20 bytes located there.
                "Library1": [
                  { start: 0, length: 20 },
                  { start: 200, length: 20 }
                ]
              }
            }
          },
          // The same layout as above.
          deployedBytecode: { },
          // The list of function hashes
          methodIdentifiers: {
            "delegate(address)": "5c19a95c"
          },
          // Function gas estimates
          gasEstimates: {
            creation: {
              codeDepositCost: "420000",
              executionCost: "infinite",
              totalCost: "infinite"
            },
            external: {
              "delegate(address)": "25000"
            },
            internal: {
              "heavyLifting()": "infinite"
            }
          }
        },
        // eWASM related outputs
        ewasm: {
          // S-expressions format
          wast: "",
          // Binary format (hex string)
          wasm: ""
        }
      }
    }
  }
}