gcc and -nostdlib

This is a discussion on gcc and -nostdlib within the C Programming forums, part of the General Programming Boards category; How can I link files manually to gcc rather than use the ones installed in the OS ? The point ...

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    gcc and -nostdlib

    How can I link files manually to gcc rather than use the ones installed in the OS ? The point is that the only the manually provided files should be used when executing the program: glibc, libgcc, linker, headers, and whatever other files are needed.

    This should be a really easy thing to do ? (I know about -static but I want to used shared libraries rather than using a huge single binary.) -nostdlib is the way to go but I cannot even get close to compiling a simple Hello World program.

    I tried something like this but I get errors: (the .so files are on my Desktop)

    myuser@linux:~/Desktop$ gcc -nostdlib libc-2.11.2.so ld-2.11.2.so libgcc_s.so.1 simple.c
    /usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000400390
    myuser@linux:~/Desktop$ ./a.out
    Hello World!
    Segmentation fault (core dumped)

    Can anybody provide a working example ?

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    myuser@linux:~/Desktop$ gcc -nostdlib -Wl,-dynamic-linker,/home/myuser/Desktop/ld-linux-x86-64.so.2,-rpath,/home/myuser/Desktop libc.so.6 libgcc_s.so.1 simple.c
    /usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000400388
    myuser@linux:~/Desktop$ ./a.out
    Hello World!
    Segmentation fault (core dumped)
    myuser@linux:~/Desktop$ ldd a.out
    linux-vdso.so.1 => (0x00007fff4b0f8000)
    libc.so.6 => /home/myuser/Desktop/libc.so.6 (0x00007f6e9d82f000)
    libgcc_s.so.1 => /home/myuser/Desktop/libgcc_s.so.1 (0x00007f6e9d619000)
    /home/myuser/Desktop/ld-linux-x86-64.so.2 => /lib64/ld-linux-x86-64.so.2 (0x00007f6e9db92000)



    In simple.c, I changed the function main to _start and the error disappears.
    It stops segfaulting by calling exit(0) at the end of the _start function.

    So, which one is it using: /home/myuser/Desktop/ld-linux-x86-64.so.2 or /lib64/ld-linux-x86-64.so.2 ?
    Last edited by pulio; 04-24-2011 at 04:57 AM.

  4. #4
    and the hat of wrongness Salem's Avatar
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    Before you start trying to drive the linker manually, study the output of
    gcc -v foo.c
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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    Quote Originally Posted by Salem View Post
    Before you start trying to drive the linker manually, study the output of
    gcc -v foo.c
    It contains a reference to: -dynamic-linker /lib64/ld-linux-x86-64.so.2

    Is it not being overrided when I call -dynamic-linker in my post above ?

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