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Check array successfully created in C

In C, there are 2 ways to create arrays:

int array[100];

and

 int * array = malloc(sizeof(int)*100);

With the second statement, it is easy to check if there is enough memory to create an array, for example:

 if(array == NULL){ goto OutOfMemory; }

But how would you verify that the first worked successfully? Assuming this works on a microcontroller, not a computer.

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2 answers

There is no such thing as a recoverable failure while allocating an array on the stack (first method). It will fail if the allocation leads to a stack overflow, after which your program is interrupted / terminated anyway.

When you allocate an array in the first way, it is allocated on the stack, usually when a function is called. If there is not enough space on the stack to allocate it, the program aborts with the / segfault error.

When you allocate the second method, you request a memory manager for memory on the heap during a malloc call.

EDIT: As @Deduplicator mentioned, if you are on a system without memory protection and you don’t have enough free space on the stack to allocate an array, this can lead to overflows and much more subtle problems (although most likely the instruction will be soon enough).

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The first part of the code stores the array on stack second stores the array in heap

The stack memory is pre-allocated to the stream, saying this, if you do not allocate a huge amount of data on the stack, you should not worry at all about the stack space.

Checking available stack size in C

Edit: In this case, you should make sure that you have enough stack (defined in your IDE / compiler / linker / proprietary software) for the most delicate calls during code execution. This may be known in advance at compile time; there is no need to check the runtime.

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