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Writing My Own Dynamic Memory Management

Frank Rosner on November 30, 2020

Introduction So far, whenever we needed some memory, e.g. to store a string, we allocated it like that: char my_string[10]. This stateme...
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cklasacrcez profile image
cklasacrcez • • Edited

Hi! I checked your algorithm on a few examples and it does not work properly at all. That is, it does not free memory properly.

// CONSOLE OUTPUT
a:00293D34
b:00292D24
c:00292D10
d:00291D00  -> Here the address should be the same as for b
f:00291D00
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     // THE CODE
    int* a = (int*)mem_alloc(sizeof(int)); 
    int* b = (int*)mem_alloc(0x1000);
    int* c = (int*)mem_alloc(sizeof(int));
    std::cout << "a:" << a << std::endl; 
    std::cout << "b:" << b << std::endl;
    std::cout << "c:" << c << std::endl;

    mem_free(b);

    int* d = (int*)mem_alloc(0x1000); // here should be adress of B 
    std::cout << "d:" << d << std::endl;

    int* e = (int*)mem_alloc(sizeof(int));
    mem_free(d);

    int* f = (int*)mem_alloc(0x1000);
    std::cout << "f:" << f << std::endl;
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Frank Rosner •

Hmmmm... I tested it a bit but didn't write any thorough unit tests. Do you know what's broken?

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Fox •

your merge_current_node_into_previous function not returning anything when it suppose to return void*

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Frank Rosner •

Oops! Thanks! :) Feel free to submit a PR :)

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Fox •

how i new to this site

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Frank Rosner •

You can open a new PR on GitHub. You can find instructions how to contribute to GitHub projects on the internet, such as dataschool.io/how-to-contribute-on...

Let me know if you get stuck :)

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Fox •

ok so is my answer is the right answer about whats broken

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Frank Rosner •

I don't know but if you make a PR / try it out we can test it :)

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Fox •

is there a private chat feature

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Frank Rosner •

I followed you so we can use dev.to/connect or you can hit me up on Twitter :)

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juanjoseamaker •

hi, if I want to boot this in my old computer, i have to use the dd command to write the img in the hard disk, because that isn't working

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Frank Rosner •

Great! I always wanted to try it but was too lazy. What did you try exactly and what was the error?

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juanjoseamaker •

I will try it again with an usb

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Raven Black •

What next paging?

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C T • • Edited

merge_current_node_into_previous (mem.c):

Update void * to void in the function signature to resolve Clang warning about non-void function not returning a value.

Cleaner console output ;)