Leaks in libc?

[Tim Kientzle]

Brandon Falk wrote:
> The simple program:
> 
> int main()
> {
>        puts("Apple cider");
> 
> Yields the following result in valgrind:
> 
> ==4703== HEAP SUMMARY:
> ==4703==     in use at exit: 4,096 bytes in 1 blocks
> ==4703==   total heap usage: 1 allocs, 0 frees, 4,096 bytes allocated
> ==4703==
> ==4703==         suppressed: 4,096 bytes in 1 blocks
> 
> Any ideas why the standard libraries are leaking like this? Is it 
> perhaps a bug with valgrind, or maybe FreeBSD automatically cleans up so 
> they took the cleanup out of their libc?

This particular leak is not at all a cause for concern.
Many parts of the system libraries use malloc() to
allocate working memory that they deliberately never
free.

In this particular case, you're seeing a 4096-byte buffer
that the stdio system allocates the first time you use it.
If you use valgrind a lot, you'll soon learn to just
ignore this and several other standard "memory leaks."

Generally, memory leaks are a cause for concern only when
they accumulate over time.  This usually happens only when
you have code that leaks memory every time it is
used (this particular example doesn't qualify since this
buffer is only allocated once regardless of how many times
you use the stdio calls) and that code is then used in a
very long-running program (such as a window manager or
web server).

Cheers,

Tim