linux/gcc: ldd functionality from inside a C/C++ program

Question

Is there some simple an efficient way to know that a given dynamically linked ELF is missing a required .so for it to run, all from the inside of a C/C++ program?

I need to program a somewhat similar functionality as ldd, without trying to execute the ELF to find out the (met/unmet) dependencies in the system. perhaps asking the ld-linux.so utility via some library? (I'm a newbie in this part of linux =)

NOTE: reading the source code of ldd was not very helpful for my intentions: it seems that ldd is in fact forking another process and executing the program.

If it's not possible to know that a program has unmet dependencies without executing it, is there some way to, at least, quickly list the .so's required for that elf all from within my program?

Thanks in advance =)

Answer 1

Have you tried dlopen function? you can use this to load a dynamic library (or, for your case, to ckeck if a library can be loaded).

Having a list of needed libraries is more difficult, take a look to handle_dynamic function on readelf source

Answer 2

As per ld.so(8), setting the environment variable LD_TRACE_LOADED_OBJECTS to a non-empty string will give ldd-like results (instead of executing the binary or library normally).

setenv("LD_TRACE_LOADED_OBJECTS", "1", 1);
FILE *ldd = popen("/lib/libz.so");