What is the Difference

[peter.devon]

hi all,

What is the Difference between realloc() and free()? Please reply soon.

Thanks
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http://www.infysolutions.com

[jpkotta]

sudo aptitude install manpages-dev
man realloc # they're on the same manpage

realloc() doesn't free memory (well, it could, but after it returns there is still allocated memory). It's functionally the same as free()ing and then malloc()ing again.

[eye208]

It's functionally the same as free()ing and then malloc()ing again.
No, it's not.

realloc() will resize an allocated block without losing its content. This is very different from free() + malloc(). Once you call free(), the content is gone.

[jpkotta]

No, it's not.

realloc() will resize an allocated block without losing its content. This is very different from free() + malloc(). Once you call free(), the content is gone.

Very true. I need to stop posting so late at night.

[snova]

Their entire purpose. ;)

malloc() allocates memory.
calloc() allocates memory and initializes it to zero.
free() releases memory.
realloc() changes the size of an allocated memory block.

[CptPicard]

realloc() changes the size of an allocated memory block.

With the gotcha that the pointer that comes back from realloc may or may not be the same pointer that went in. Content is not lost, but there can be copying going on in the background.