addon with LD_PRELOAD hooking is not working

[cinyoung hur]

Hello,

I'm testing addon with LD_PRELOAD hooking.

In the test, I made hooking object for fopen call.

When I test with this example, fopen hooking worked.

#include <stdio.h>

int main()

{}

    // ld_preload test

    FILE* fd = NULL;

    printf("Calling the fopen() function. \n");

    fd = fopen("test.txt", "r");

    if(!fd) {

      printf("ok\n");

    }

    printf("fopen() succeeded\n");

}

But, if I apply this within node addons, hooking didn't work.

NAN_METHOD(MyObject::New) {

  NanScope();

  if (args.IsConstructCall()) {

    // Invoked as constructor: `new MyObject(...)`

    MyObject* obj = new MyObject();

    obj->Wrap(args.This());

    // ld_preload test

    FILE* fd = NULL;

    printf("Calling the fopen() function. \n");

    fd = fopen("test.txt", "r");

    if(!fd) {

      printf("null\n");

    }

    printf("fopen() succeeded\n");

    

    NanReturnValue(args.This());

  } 

}

Node addon documents say that Node statically compiles all its dependencies into the executable.

http://nodejs.org/docs/latest/api/addons.html

Is that why LD_PRELOAD is not working?

Please guide me to solve this problem.

[Floby]

Yes, LD_PRELOAD only works with dynamically linked libraries.

[Floby]

That being said

$ nm `which node` | grep fopen

                 U fopen64@@GLIBC_2.2.5

                 U fopen@@GLIBC_2.2.5

seems to indicate that fopen is indeed dynamically linked.

On Thursday, 12 February 2015 07:05:01 UTC+1, cinyoung hur wrote: