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<title>Memory Usage (libffi: the portable foreign function interface library)</title>
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<div class="chapter" id="Memory-Usage">
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<span id="Memory-Usage-1"></span><h2 class="chapter">3 Memory Usage</h2>
<p>Note that memory allocated by <code>ffi_closure_alloc</code> and freed by
<code>ffi_closure_free</code> does not come from the same general pool of
memory that <code>malloc</code> and <code>free</code> use. To accomodate security
settings, <code>libffi</code> may aquire memory, for example, by mapping
temporary files into multiple places in the address space (once to
write out the closure, a second to execute it). The search follows
this list, using the first that works:
</p>
<ul>
<li> A anonymous mapping (i.e. not file-backed)
</li><li> <code>memfd_create()</code>, if the kernel supports it.
</li><li> A file created in the directory referenced by the environment variable
<code>LIBFFI_TMPDIR</code>.
</li><li> Likewise for the environment variable <code>TMPDIR</code>.
</li><li> A file created in <code>/tmp</code>.
</li><li> A file created in <code>/var/tmp</code>.
</li><li> A file created in <code>/dev/shm</code>.
</li><li> A file created in the user’s home directory (<code>$HOME</code>).
</li><li> A file created in any directory listed in <code>/etc/mtab</code>.
</li><li> A file created in any directory listed in <code>/proc/mounts</code>.
</li></ul>
<p>If security settings prohibit using any of these for closures,
<code>ffi_closure_alloc</code> will fail.
</p>
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