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<a name="Thread_002dsafety-of-the-runtime-library"></a>
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Next: <a href="Data-consistency-and-durability.html#Data-consistency-and-durability" accesskey="n" rel="next">Data consistency and durability</a>, Previous: <a href="Internal-representation-of-LOGICAL-variables.html#Internal-representation-of-LOGICAL-variables" accesskey="p" rel="prev">Internal representation of LOGICAL variables</a>, Up: <a href="Compiler-Characteristics.html#Compiler-Characteristics" accesskey="u" rel="up">Compiler Characteristics</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Thread_002dsafety-of-the-runtime-library-1"></a>
<h3 class="section">5.3 Thread-safety of the runtime library</h3>
<a name="index-thread_002dsafety_002c-threads"></a>

<p>GNU Fortran can be used in programs with multiple threads, e.g. by
using OpenMP, by calling OS thread handling functions via the
<code>ISO_C_BINDING</code> facility, or by GNU Fortran compiled library code
being called from a multi-threaded program.
</p>
<p>The GNU Fortran runtime library, (<code>libgfortran</code>), supports being
called concurrently from multiple threads with the following
exceptions. 
</p>
<p>During library initialization, the C <code>getenv</code> function is used,
which need not be thread-safe.  Similarly, the <code>getenv</code>
function is used to implement the <code>GET_ENVIRONMENT_VARIABLE</code> and
<code>GETENV</code> intrinsics.  It is the responsibility of the user to
ensure that the environment is not being updated concurrently when any
of these actions are taking place.
</p>
<p>The <code>EXECUTE_COMMAND_LINE</code> and <code>SYSTEM</code> intrinsics are
implemented with the <code>system</code> function, which need not be
thread-safe.  It is the responsibility of the user to ensure that
<code>system</code> is not called concurrently.
</p>
<p>Finally, for platforms not supporting thread-safe POSIX functions,
further functionality might not be thread-safe.  For details, please
consult the documentation for your operating system.
</p>


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