Memory allocation

This is a discussion on Memory allocation within the C Programming forums, part of the General Programming Boards category; How to check the memory allocated using malloc function. Code: int *mem; mem=(int *)malloc(sizeof(int)); How to check the memory allocated ...

  1. #1
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    Memory allocation

    How to check the memory allocated using malloc function.

    Code:
    int *mem;
    mem=(int *)malloc(sizeof(int));
    How to check the memory allocated to mem.

  2. #2
    C++まいる!Cをこわせ! Elysia's Avatar
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    The size you mean? There's no portable way to do that. Each library implementation is free to add a function to get the size, but is not required to.
    Better to keep check of the size manually.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    How to check it manually?

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    Cogito Ergo Sum
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    Just do it theoretically, int is 4 bytes. The rest is easy.

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    C++まいる!Cをこわせ! Elysia's Avatar
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    The actual size is not guaranteed to be "just" 4 bytes. It may be more. But as I mentioned, there's no "100% guaranteed" way to check it. It differs from each implementation.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    Quote Originally Posted by sarathius View Post
    How to check it manually?
    What exactly do you want to "check"? There are only two valid return values from malloc(): NULL for a failed allocation, and a valid pointer to a block of the size you requested, which is ANY other value than NULL. [Assuming of course we are talking about a malloc() that is implemented by a normal system library, rather than "I built my own malloc function, and I want to check if it works"].

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