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0 pointsmturmon13y ago0 comments

Question 10 is just crazy broken. I'm not a standards expert, but I don't think argv[0] is guaranteed to be big enough to hold the 7 characters (plus \0) of NewName (i.e., even if it is writable, it may not be big enough).

As the comments said, argv[0] does not have to point to writable memory, because argc can be 0. In this case argv[0] is supposed to be NULL, which would segfault the program.

If you had to solve this question (it would be better not to ask it, because you don't learn much), I think the solution:

   argv[0] = "NewName";

would be better. It's at least shorter.

0 comments

ambrice13y ago

It also wouldn't work. This just reassigns your local copy of argv[0] to a different memory location. Also, in what circumstances can argc be 0?

tedunangst13y ago

    int main()
    {
        char *args[] = { 0 };
        execve("./zero", args, 0L);
    }

zero will have argc == 0.

mturmonOP13y ago

On my MBP with gcc 4.2.1, it does work -- I tried it before posting. (Your interpretation of what it does is correct.)

tedunangst13y ago

I think the best solution would be something like "Hope setproctitle() is available and use it".

j / k navigate · click thread line to collapse

0 pointsmturmon13y ago0 comments

As the comments said, argv[0] does not have to point to writable memory, because argc can be 0. In this case argv[0] is supposed to be NULL, which would segfault the program.

If you had to solve this question (it would be better not to ask it, because you don't learn much), I think the solution:

   argv[0] = "NewName";

would be better. It's at least shorter.

0 comments

ambrice13y ago

It also wouldn't work. This just reassigns your local copy of argv[0] to a different memory location. Also, in what circumstances can argc be 0?

tedunangst13y ago

    int main()
    {
        char *args[] = { 0 };
        execve("./zero", args, 0L);
    }

zero will have argc == 0.

mturmonOP13y ago

On my MBP with gcc 4.2.1, it does work -- I tried it before posting. (Your interpretation of what it does is correct.)

tedunangst13y ago

I think the best solution would be something like "Hope setproctitle() is available and use it".

j / k navigate · click thread line to collapse