character strings

This is a discussion on character strings within the C Programming forums, part of the General Programming Boards category; i'm just wondering when it's ok to use a declaration such as char *string; instead of something like char string[BUFSIZ]; ...

  1. #1
    Advanced Novice linucksrox's Avatar
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    character strings

    i'm just wondering when it's ok to use a declaration such as char *string; instead of something like char string[BUFSIZ]; because when I try to store user input into the first one it has a tendency to give me trouble. but the second one works fine. as far as i know the first one doesn't assign any memory to the pointer because it doesn't know how much, but i have seen plenty of code that doesn't use anything like malloc to assign memory before storing strings, so why am i having problems? if it matters, i'm on windows 2k pro using dev-cpp 4.9.8.9

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    and the hat of wrongness Salem's Avatar
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    > but i have seen plenty of code that doesn't use anything like malloc to assign memory before storing strings
    All such code is wrong - unfortunately, much of it originates on DOS where uninitialised pointers could be used with abandon (for a short while at least).

    Every pointer variable needs a malloc of some sort, or be made to point at some other part of memory.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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    & the hat of GPL slaying Thantos's Avatar
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    i'm just wondering when it's ok to use a declaration such as char *string; instead of something like char string[BUFSIZ];
    Only when you initalize the pointer immediately such as:
    Code:
    char *str = "Hello Bob";
    Of course then you can not modify the string in any way, shape, or form. A better way would be
    Code:
     const char *str = "Hello Bob";
    Of course with both you are just initalizing the pointer to the location of "Hello Bob".

    If you want to make any changes to the contents then you have to malloc.

    Remember all variables should be initalized upon declaration including (and especially) pointers.

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    Advanced Novice linucksrox's Avatar
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    ok that all makes sense, but then I wonder why you guys are so picky when people post stuff like void main() and then the same people go ahead and post code like
    Code:
    int main()
    {
      char *stuff;
    
      fgets(stuff, 256, stdin);
      printf("you entered %s.\n");
    
      return 0;
    }
    i just made that up but i mean that's the kinda stuff you see from the same people who bash others for doing void main() (which by the way i know is wrong)
    and i'll remember to initialize all my auto variables upon declaration

  5. #5
    and the hat of wrongness Salem's Avatar
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    Oh we pick those up as well
    Even more so if they use gets() instead of fgets()
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  6. #6
    & the hat of GPL slaying Thantos's Avatar
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    We are equal opportunity bashers

  7. #7
    Advanced Novice linucksrox's Avatar
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    awesome, so i'll remember to keep using void main() and gets() whenever possible but DARN you for using scanf() for user input!

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