c - malloced array VS. variable-length-array -

this question has answer here:

there 2 ways allocate memory array, of size unknown @ beginning. common way using malloc this

int * array; ... // when know size array = malloc(size*sizeof(int));

but it's valid in c99 define array after know size.

... // when know size int array[size];

are absolutely same?

no they're not absolutely same. while both let store same number , type of objects, keep in mind that:

you can free() malloced array, can't free() variable length array (although goes out of scope , ceases exist once enclosing block left). in technical jargon, have different storage duration: allocated malloc versus automatic variable length arrays.
although c has no concept of stack, many implementation allocate variable length array stack, while malloc allocates heap. issue on stack-limited systems, e.g. many embedded operating systems, stack size on order of kb, while heap larger.
it easier test failed allocation malloc variable length array.
malloced memory can changed in size realloc(), while vlas can't (more precisely executing block again different array dimension--which loses previous contents).
a hosted c89 implementation supports malloc().
a hosted c11 implementation may not support variable length arrays (it must define __stdc_no_vla__ integer 1 according c11 6.10.8.3).
everything else have missed :-)

KHS