Thread: using gdb

  1. #1
    Registered User
    Join Date
    Feb 2005
    Posts
    19

    using gdb

    Hello everyone,

    I'm trying to learn to use gdb v5.3-25mdk (Mandrake Linux).

    I wrote a test.c file according to instructions I found in "Sam's Teach Youself
    Linux Programming in 24 Hours"

    The test.c code is supposed to compile but produce a segmentation fault upon
    execution (which it does) as well as a core file (which I don't think it does).

    No core file is produced (that I can find with either ls or ls -a)???


    Here's the code:

    Code:
    static void fun1(void) {
       char *cp = 0;
    
       *cp = '!';   /*intentional bad dereference to produce segmentation fault*/
    }
    
    int main (int argc,char **argv) {
        fun1( );
        return 0;
    
    }
    The command for compiling is: bash$ gcc -g -D_GNU_SOURCE test.c -o test

    It compiles without error or warning.

    From bash$ ./test, I get "Segmentation fault".

    No core file.

    I ran bash$ gdb ./test core

    gdb tells me "/dir/dir/core no such file or directory"

    Have things changed for gdb since the book was published in 1999?

    Thanks

  2. #2
    Registered Luser cwr's Avatar
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    Sydney, Australia
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    It's nothing to do with gdb. Linux can be set to dump core on segmentation fault, or not. Try typing ulimit -c 999999 before running the program. Then it should say "Segmentation fault - core dumped" or similar.

  3. #3
    Registered User
    Join Date
    Feb 2005
    Posts
    19
    That worked!

    Thanks.

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