NodeJS native module - how to remove debug symbols

Question

I'm writing a native module for Node but would like to remove the debugging information. I'm using node-gyp to build the module.

It's doing a release build, but still, the symbol table is included in the output file.

So I need to remove it with the strip Unix command after the build. Is there a way to remove it in the build itself - ie. specify something in the .gyp file?

Furthermore, even after stripping the debug symbols, I can still use

strings [node-module]

And it lists the names of my functions. Is it possible to remove these also?

This is the command I use to build the native module:

node-gyp rebuild --target=v8.9.4

And this is my binding.gyp:

{
  "targets": [
    {
      "libraries": [
          "/usr/lib/x86_64-linux-gnu/libudev.so",
          "/usr/lib/x86_64-linux-gnu/libboost_regex.so.1.58.0"
      ],
      "target_name": "utils",
      "sources": [ "src/native/utils.cpp" ]
    }
  ]
}

Thanks!

Answer 1

As you probably know, a node native module is a dynamic library. You cannot strip the dynamic symbol table from a dynamic library because the dynamic symbol table is necessary at runtime for dynamically linking the library. Even strip --strip-all will not remove the dynamic symbol table. strip --strip-all or strip --strip-unneeded strips everything that can be stripped from a dynamic library. Adding -g0 to the compilation flags eliminates all debugging information, but symbol tables contain more than debugging information.

You can instruct the linker to do the same thing as strip --strip-all at linktime by passing it the option -s|--strip-all. To do this, your binding.gyp would be:

{
    "targets": [
    {
        "libraries": [
            "/usr/lib/x86_64-linux-gnu/libudev.so",
            "/usr/lib/x86_64-linux-gnu/libboost_regex.so.1.58.0"
        ],
        "target_name": "utils",
        "ldflags" : [ "-Wl,-s" ],
        "sources": [ "src/native/utils.cpp" ],
    }
  ]
}

The resulting node module is then as stripped as a shared library can be:

$ file ./build/Release/utils.node
./build/Release/utils.node: ELF 64-bit LSB shared object, x86-64, \
version 1 (SYSV), dynamically linked, \
BuildID[sha1]=eb53cee5839c71b41176bc7a852802035009e8ae, stripped
                                                        ^^^^^^^^

Answer 2

I have searched a bit and there may be a brute force solution of specifying the compiler flag -g0 manually. Take a look here:https://github.com/nodejs/node-gyp/issues/26 . So following Your example and advices given in the github issue the input file should be like this:

{
  "targets": [
    {
      "libraries": [
          "/usr/lib/x86_64-linux-gnu/libudev.so",
          "/usr/lib/x86_64-linux-gnu/libboost_regex.so.1.58.0"
      ],
      "target_name": "utils",
      "cflags_cc": [ "-g0" ]
      "sources": [ "src/native/utils.cpp" ]
    }
  ]
}

Sadly, there is no way for me to test it and it is not platform independant.