free(): invalid pointer:

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  • Cyron
    #1

    free(): invalid pointer:

    Hello friends,

    I'm getting a bizaare glibc error referencing free -- I malloc a
    chunk of memory and then later when I try to free it is when the
    program aborts. I've added some debug code to the source and find
    that my pointer i get from malloc matches the one that I'm calling
    free with -- and there is no possibility that have i have previously
    freed the memory because there is only 1 free call in the entire
    source (surrounded by debug printfs) so I don't know what is going on.
    Any insight?

    Thanks,
    Mike

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    • gw7rib@aol.com
      #2
      Re: free(): invalid pointer:

      On 30 Sep, 21:03, Cyron <mdigit...@yaho o.comwrote:
      Hello friends,
      >
      I'm getting a bizaare glibc error referencing free -- I malloc a
      chunk of memory and then later when I try to free it is when the
      program aborts. I've added some debug code to the source and find
      that my pointer i get from malloc matches the one that I'm calling
      free with -- and there is no possibility that have i have previously
      freed the memory because there is only 1 free call in the entire
      source (surrounded by debug printfs) so I don't know what is going on.
      Any insight?
      Are you perhaps writing to memory just outside the memory you have
      allocated?

        Comment

        • Flash Gordon
          #3
          Re: free(): invalid pointer:

          Cyron wrote, On 30/09/07 21:03:
          I'm getting a bizaare glibc error referencing free -- I malloc a
          chunk of memory and then later when I try to free it is when the
          program aborts. I've added some debug code to the source and find
          <snip>

          You are probably writing beyond the end or before the start of the
          allocated space. If you can get the program down to a reasonably small
          chunk of code that shows the problem we can take a look at it.
          --
          Flash Gordon

            Comment

            • Richard Tobin
              #4
              Re: free(): invalid pointer:

              In article <1191182600.392 335.16830@50g20 00hsm.googlegro ups.com>,
              Cyron <mdigitale@yaho o.comwrote:
              I'm getting a bizaare glibc error referencing free -- I malloc a
              >chunk of memory and then later when I try to free it is when the
              >program aborts. I've added some debug code to the source and find
              >that my pointer i get from malloc matches the one that I'm calling
              >free with -- and there is no possibility that have i have previously
              >freed the memory because there is only 1 free call in the entire
              >source (surrounded by debug printfs) so I don't know what is going on.
              You almost certainly have some kind of out-of-bounds pointer error.
              Your first choice for finding such things, if you have one available,
              is a memory-reference-checking tool such as valgrind. From your
              reference to glibc, I assume you're using Linux, so valgrind should be
              available. I find that 90% of the time it directs me straight to the
              bug.

              -- Richard
              --
              "Considerat ion shall be given to the need for as many as 32 characters
              in some alphabets" - X3.4, 1963.

                Comment

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