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Editorial Team
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Asked: 2026-05-14T00:01:35+00:00

When malloc is called, the size is stored adjacent to the allocated block so

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When malloc is called, the size is stored adjacent to the allocated block so that free will know how much to free etc ( http://c-faq.com/malloc/freesize.html ).

My question is, Say we have dynamically allocated memory and later in the code we increment the pointer 

 pointer++

And then later, if i call a 

free(pointer)

what memory does actually get freed up.

Is it number of allocated bytes starting from the current address pointed by ‘pointer’ or from the base address to which it has been allocated.

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1 Answer

  1. Editorial Team

    You need to free() the same pointer as you received from malloc(). Incrementing, altering or changing it is undefined behaviour, that is usually a segmentation fault.

    Think of the pointer you receive as a book from a library. You get home and read it. Afterwards you remove the front page and the book’s back and hand it back to the librarian. Will he accept it or are you in serious trouble now? 😉

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