valgrind reporting non-freed blocks

Question

Valgrind leak file summary:

ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
malloc/free: in use at exit: 45,065 bytes in 12 blocks.
malloc/free: 161 allocs, 149 frees, 53,301 bytes allocated.
searching for pointers to 12 not-freed blocks.
checked 583,764 bytes.

One of this 12 blocks is from strdup. I should have freed things allocated by strdup, I agree.

My question is, in general, is it bad to leave non-freed blocks? Is it called mem-leak technically?

Are they not given back to the system once program dies?

Please advise.

Edit 0: Thanks for your responses. How can I know where are these 12 non-freed blocks? And what part of code is generating them?

Answer 1

It is given back to the system.

It it not technically a memory leak if you have a reference to the memory. To be a memory leak you must de-reference the memory.

void *str = malloc(10);
str = NULL;

It is bad to leave non-freed blocks at any point. If the program is finishing it, it might not be that bad, but it is not good for any future change you might do (e.g.: extract a function and call it multiple times).

Also, getting rid of all memory leaks will make it easier to track with valgrind any new (and relevant) one.