<term><envar>LDFLAGS</envar></term>
       <listitem>
        <para>
         options to use when linking either executables or shared libraries
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-ldflags-ex">
       <term><envar>LDFLAGS_EX</envar></term>
       <listitem>
        <para>
         additional options for linking executables only
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-ldflags-sl">
       <term><envar>LDFLAGS_SL</envar></term>
       <listitem>
        <para>
         additional options for linking shared libraries only
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-llvm-config">
       <term><envar>LLVM_CONFIG</envar></term>
       <listitem>
        <para>
         <command>llvm-config</command> program used to locate the
         <productname>LLVM</productname> installation
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-msgfmt">
       <term><envar>MSGFMT</envar></term>
       <listitem>
        <para>
         <command>msgfmt</command> program for native language support
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-perl">
       <term><envar>PERL</envar></term>
       <listitem>
        <para>
         Perl interpreter program.  This will be used to determine the
         dependencies for building PL/Perl.  The default is
         <command>perl</command>.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-python">
       <term><envar>PYTHON</envar></term>
       <listitem>
        <para>
         Python interpreter program.  This will be used to determine the
         dependencies for building PL/Python.  If this is not set, the
         following are probed in this order:
         <literal>python3 python</literal>.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-tclsh">
       <term><envar>TCLSH</envar></term>
       <listitem>
        <para>
         Tcl interpreter program.  This will be used to
         determine the dependencies for building PL/Tcl.
         If this is not set, the following are probed in this
         order: <literal>tclsh tcl tclsh8.6 tclsh86 tclsh8.5 tclsh85
         tclsh8.4 tclsh84</literal>.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry id="configure-envvars-xml2-config">
       <term><envar>XML2_CONFIG</envar></term>
       <listitem>
        <para>
         <command>xml2-config</command> program used to locate the
         libxml2 installation
        </para>
       </listitem>
      </varlistentry>
     </variablelist>
    </para>

    <para>
     Sometimes it is useful to add compiler flags after-the-fact to the set
     that were chosen by <filename>configure</filename>.  An important example is
     that <application>gcc</application>'s <option>-Werror</option> option cannot be included
     in the <envar>CFLAGS</envar> passed to <filename>configure</filename>, because
     it will break many of <filename>configure</filename>'s built-in tests.  To add
     such flags, include them in the <envar>COPT</envar> environment variable
     while running <filename>make</filename>.  The contents of <envar>COPT</envar>
     are added to the <envar>CFLAGS</envar>, <envar>CXXFLAGS</envar>, and <envar>LDFLAGS</envar>
     options set up by <filename>configure</filename>.  For example, you could do
<screen>
<userinput>make COPT='-Werror'</userinput>
</screen>
     or
<screen>
<userinput>export COPT='-Werror'</userinput>
<userinput>make</userinput>
</screen>
    </para>

    <note>
     <para>
      If using GCC, it is best to build with an optimization level of
      at least <option>-O1</option>, because using no optimization
      (<option>-O0</option>) disables some important compiler warnings