Sequential memory allocation

Question

I'm planning a application that allocates a lot of variables in memory. In difference from another "regular" application, I want this memory be allocated in specific memory blocks of 4096 bytes. My allocated vars must be placed in memory sequentially. One after another, in order to fill the whole allocated memory.

For example, I'm allocating a region (4096 bytes) in memory and this region is ready for my further use. From now, each time that my application creates a new variable in memory (which is probably made in "regular" application with malloc), this variable will be placed in free space in my memory region.

This sequential memory allocation is similare to how an array allocation works. But, in my case, I need an array that will be able to contain many types of data (string, byte, int, ...).

One possible solution is to achieve this is by pointer arithmetics. I want to avoid this method, this may insert a lot of bugs in my application.

Maybe someone solved this problem before?

Thank you!

Answer 1

malloc() by no means guarantees that subsequent allocated blocks are on sequential memory address. Even worse, most implementations use a small number of bytes before and/or after the allocated block for 'housekeeping'. This means that, even if you're lucky that addresses are sequential, there will be small gaps in between the blocks. So the actual allocated blocks are slightly bigger to make space for those 'housekeeping' bytes.

As you suggest, you'll need to write some code yourself and write a few functions with malloc(), realloc(), ... You can hide all the logic in these functions and should not make your application code using these functions more complex compared to using malloc() if it did what you wanted.

Important questions: Why do you need to have these blocks adjacent to each other? What about freeing blocks?