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<h3 class="section">5.3 Thread-safety of the runtime library</h3>
<p><a name="index-thread_002dsafety_002c-threads-304"></a>
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>The GNU Fortran runtime library, (<code>libgfortran</code>), supports being
called concurrently from multiple threads with the following
exceptions.
<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>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>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.
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