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- <html>
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- <title>free</title>
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- <h2 align=center>free</h2>
- <h4 align=center>OS/161 Reference Manual</h4>
- <h3>Name</h3>
- free - release/deallocate memory
- <h3>Library</h3>
- Standard C Library (libc, -lc)
- <h3>Synopsis</h3>
- #include <stdlib.h><br>
- <br>
- void<br>
- malloc(void *<em>ptr</em>);
- <h3>Description</h3>
- free releases a block of memory previously allocated with
- <A HREF=malloc.html>malloc</A>, <A HREF=calloc.html>calloc</A>,
- or <A HREF=realloc.html>realloc</A>.
- <p>
- Once free has been called, <em>ptr</em> is no longer valid and
- attempts to dereference it result in undefined behavior.
- (Pedantically, in fact, even using the <strong>value</strong> of
- <em>ptr</em> may produce undefined behavior.) Passing <em>ptr</em> to
- free a second or subsequent time (unless of course the same pointer
- value is again returned from malloc) is particularly likely to provoke
- undefined behavior in most implementations.
- <p>
- free(NULL) has no effect.
- <p>
- In practice it is desirable for implementations of free to detect, to
- the extent practically possible, pointers that were not previously
- allocated by one of the above functions or that are passed to free
- multiple times. However, this can be difficult and there is no useful
- standard mechanism for error reporting.
- <p>
- free does not necessarily unmap free memory or return it to the
- operating system, but may do so if it chooses.
- <h3>Return Values</h3>
- free returns no value.
- <h3>See Also</h3>
- <A HREF=calloc.html>calloc</A>,
- <A HREF=malloc.html>malloc</A>,
- <A HREF=realloc.html>realloc</A>
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