编译JVMTI代理（在OSX Snow Leopard上使用GCC） [英] Compiling JVMTI agent (using GCC, on OSX Snow Leopard)

问题描述

我试图在Snow Leopard上使用g ++命令来构建JVMTI代理，并且出现以下错误：

I am trying to build a JVMTI agent using the g++ command on Snow Leopard and I get the following error:

$ g++ -o agent.so -I `/usr/libexec/java_home`/include agent.cpp

Undefined symbols: "_main", referenced from: start in crt1.10.6.o ld:
symbol(s) not found collect2: ld returned 1 exit status

当谈到gcc和C ++编程时，我是个新手，所以我不知道这个错误的含义。代理本身是非常基本的：

I am a total novice when it comes to gcc and C++ programming so I have no idea what that error means. The agent itself is extremely basic:

      #include 
      #include 

      JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM *vm, char *options, void *reserved)
      {
          std::cout <<"Loading aspect..." <<std::endl;
          return JNI_OK;
      }

任何有关该消息的帮助都将不胜感激。

Any help with the message would be greatly appreciated.

推荐答案

你提供给g ++的命令行选项告诉它你正在尝试构建一个可执行文件，而不是共享库。 g ++抱怨你没有定义 main 函数，因为每个可执行文件都需要一个。

The command line options you've supplied to g++ are telling it that you're trying to build an executable, not a shared library. g++ is complaining that you haven't defined a main function, as every executable requires one.

编译共享带-c标志的库，以便g ++知道要建立一个库，即编译和组装你的代码，但不要试图将它链接到一个可执行文件中。

Compile your shared library with the -c flag so that g++ knows to build a library, i.e. compile and assemble your code, but don't try to link it into an executable file.

g++ -c -o agent.so -I `/usr/libexec/java_home`/include agent.cpp

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