gcc and -o -c

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Thread: gcc and -o -c

  1. #1
    Join Date
    Apr 2003

    gcc and -o -c

    Im trying to make some small shared libs.

    One of my C files needs 2 others, so i want to compile these 3 into a object file.

    Heres what i get:
    gcc -o str_move.o -c str_move.c str_remove.c str_insert.c
    gcc: cannot specify -o with -c or -S and multiple compilations
    make: *** [str_move.o] Error 1
    What wrong? What should i do?


  2. #2
    Join Date
    Apr 2003
    Actually, a shared lib for those 2 deps was already made. How could I make gcc use them instead of compiling the code in?

  3. #3
    Join Date
    Nov 2002
    is it not clear what you need but I'm sure you'd better to:

    gcc -o str_move.o -c str_move.c
    gcc -o str_remove.o -c str_remove.c
    gcc -o str_insert.o -c str_insert.c

    then link all togheter:

    gcc -o executable str_move.o str_remove.o str_insert.o

    in this way you build an executable, if you want a shared library to be build, you have to compile with fPIC (position independent code) and then link with some gcc link option (currently I do not have gcc man available)

    tell me more about your problem


  4. #4
    Join Date
    Jun 2003
    Lancaster, SC
    you can't link .c files, they must be compiled into .o files, like micio said...and you need to tell us more about your predicament
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  5. #5
    Join Date
    Jul 2003
    It doesn't matter if "one c file needs another" because -c means you compile without linking. Everywhere in the str_move.o file where a function needs to call a function in str_insert.o is basically some sentence that says "Hey linker, when you link me make sure the function str_insert( ) is compiled somewhere with all of the object files you have to work with." Assuming you include str_insert.o in the list of parameters you pass to gcc when making and executable, when gcc does the linking it will find that function. If you don't include str_insert.o, it will claim there is an undefined reference to str_insert( ).

    gcc -c str_move.c
    gcc -c str_remove.c
    gcc -c str_insert.c
    ar r libstr.a str_move.o str_remove.o str_insert.o
    ranlib libstr.a

    For a static library

    gcc -D_REENTRANT -fPIC -c str_move.c
    gcc -D_REENTRANT -fPIC -c str_remove.c
    gcc -D_REENTRANT -fPIC -c str_insert.c
    gcc -shared -Wl,-soname,libstr.so.1 -o libstr.so.1.0.0 str_move.o str_remove.o str_insert.o

    for shared
    Last edited by grady; 10-20-2003 at 02:31 PM.

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