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Using pointer after free()
(6 answers)
Closed 6 years ago.
I allocated memory for pointer using malloc function. I had deallocate memory using free. But whenever I'm trying to print the content of pointer it prints the content.
Then what is the use of free()?
free() just marks the memory as available (as in, it can be used for further allocations). It does not removes the content of the memory.
That said, you should not access the content of a freed memory, as it is Undefined Behavior.
Related
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Should I free memory before exit?
(5 answers)
What REALLY happens when you don't free after malloc before program termination?
(20 answers)
Closed 8 months ago.
In a C program, if I try to use malloc and for some reason the pointer is NULL, I will terminate the program with exit(1); as without that block of memory the program is essentially unusable. Upon using exit(1); should I be releasing all of the memory I had allocated during the program or does that happen automatically?
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Difference between malloc and calloc?
(14 answers)
Closed 1 year ago.
From Wikipedia:
malloc() does not initialize the memory allocated, while calloc()
guarantees that all bytes of the allocated memory block have been
initialized to 0.
I understand that malloc doesn't initialize the memory to anything, but I have to wonder, why is this the case? Was there a specific reason behind this design decision? It seems like a bit of an antipattern to use calloc(sizeof(T), 1) in my humble opinion and I want to understand the intention.
Because we really don't want to waste all that CPU. It's sooo expensive.
Yes really. You're going to overwrite it anyway.
This question already has answers here:
How to find uninitialized variables in C on Linux?
(2 answers)
How to check if a variable has been initialized in C?
(3 answers)
Closed 2 years ago.
I pass a pointer to my function but if this is not initialized I get, obviously, segmentation fault. I could solve this porblem by assigning NULL to that pointer when declared (or, in general, before passing it to my function), but if I wanted my funtion to detect that pointer is not initialized?
The common way is to always initialize pointers to NULL when you first declare them or after freeing them so that whenever you have to manipulate a pointer, if it's equal to NULL, you know that you have to allocate them and populate their data.
This question already has answers here:
Freeing global variable
(2 answers)
Closed 7 years ago.
Say I declare a global array int arr[10]; Should I free it somehow in the end?
You need not free it.You should use free() only when you have use malloc().
No. You can't free it and you don't need to. arr is in static storage which means that it is created on program startup and destroyed on program termination. Explicit freeing is neither possible nor required as the storage is automatically freed on program termination.
This question already has answers here:
Why are two different concepts both called "heap"? [duplicate]
(9 answers)
What is a Memory Heap?
(8 answers)
Closed 9 years ago.
Can anyone explain why the pool of memory managed by malloc() / free() is called a heap?
Based on [1]: http://www.google.com/url?q=http://gee.cs.oswego.edu/dl/html/malloc.html&sa=D&sntz=1&usg=AFQjCNHaQLotbBKKwYqxiiYWN1146BWzFw "Doug Lea's explanation of how his malloc() works",
it's not obvious that the data structure which we call a "heap" is being used at all.
Do we call it a "heap" because it's common for malloc() implementations to use best-fit selection of the memory chunk to return, and that's historically been implemented using a min-heap of chunks, sorted by chunk size?