339 lines
11 KiB
Plaintext
339 lines
11 KiB
Plaintext
<!--
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$PostgreSQL: pgsql/doc/src/sgml/dfunc.sgml,v 1.27 2003/11/29 19:51:36 pgsql Exp $
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-->
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<sect2 id="dfunc">
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<title id="dfunc-title">Compiling and Linking Dynamically-Loaded Functions</title>
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<para>
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Before you are able to use your
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<productname>PostgreSQL</productname> extension functions written in
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C, they must be compiled and linked in a special way to produce a
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file that can be dynamically loaded by the server. To be precise, a
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<firstterm>shared library</firstterm> needs to be
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created.<indexterm><primary>shared library</></indexterm>
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</para>
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<para>
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For information beyond what is contained in this section
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you should read the documentation of your
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operating system, in particular the manual pages for the C compiler,
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<command>cc</command>, and the link editor, <command>ld</command>.
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In addition, the <productname>PostgreSQL</productname> source code
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contains several working examples in the
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<filename>contrib</filename> directory. If you rely on these
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examples you will make your modules dependent on the availability
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of the <productname>PostgreSQL</productname> source code, however.
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</para>
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<para>
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<indexterm><primary>PIC</></> Creating shared libraries is generally
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analogous to linking executables: first the source files are
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compiled into object files, then the object files are linked
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together. The object files need to be created as
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<firstterm>position-independent code</firstterm>
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(<acronym>PIC</acronym>),<indexterm><primary>PIC</></> which
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conceptually means that they can be placed at an arbitrary location
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in memory when they are loaded by the executable. (Object files
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intended for executables are usually not compiled that way.) The
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command to link a shared library contains special flags to
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distinguish it from linking an executable. --- At least this is the
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theory. On some systems the practice is much uglier.
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</para>
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<para>
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In the following examples we assume that your source code is in a
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file <filename>foo.c</filename> and we will create a shared library
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<filename>foo.so</filename>. The intermediate object file will be
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called <filename>foo.o</filename> unless otherwise noted. A shared
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library can contain more than one object file, but we only use one
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here.
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</para>
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<!--
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Note: Reading GNU Libtool sources is generally a good way of
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figuring out this information. The methods used within PostgreSQL
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source code are not necessarily ideal.
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-->
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<variablelist>
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<varlistentry>
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<term><systemitem class="osname">BSD/OS</></term>
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<indexterm><primary>BSD/OS</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag to create <acronym>PIC</acronym> is
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<option>-fpic</option>. The linker flag to create shared
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libraries is <option>-shared</option>.
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<programlisting>
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gcc -fpic -c foo.c
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ld -shared -o foo.so foo.o
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</programlisting>
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This is applicable as of version 4.0 of
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<systemitem class="osname">BSD/OS</>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">FreeBSD</></term>
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<indexterm><primary>FreeBSD</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag to create <acronym>PIC</acronym> is
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<option>-fpic</option>. To create shared libraries the compiler
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flag is <option>-shared</option>.
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<programlisting>
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gcc -fpic -c foo.c
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gcc -shared -o foo.so foo.o
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</programlisting>
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This is applicable as of version 3.0 of
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<systemitem class="osname">FreeBSD</>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">HP-UX</></term>
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<indexterm><primary>HP-UX</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag of the system compiler to create
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<acronym>PIC</acronym> is <option>+z</option>. When using
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<application>GCC</application> it's <option>-fpic</option>. The
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linker flag for shared libraries is <option>-b</option>. So
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<programlisting>
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cc +z -c foo.c
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</programlisting>
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or
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<programlisting>
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gcc -fpic -c foo.c
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</programlisting>
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and then
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<programlisting>
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ld -b -o foo.sl foo.o
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</programlisting>
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<systemitem class="osname">HP-UX</> uses the extension
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<filename>.sl</filename> for shared libraries, unlike most other
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systems.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">IRIX</></term>
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<indexterm><primary>IRIX</><secondary>shared library</></>
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<listitem>
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<para>
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<acronym>PIC</acronym> is the default, no special compiler
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options are necessary. The linker option to produce shared
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libraries is <option>-shared</option>.
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<programlisting>
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cc -c foo.c
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ld -shared -o foo.so foo.o
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">Linux</></term>
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<indexterm><primary>Linux</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag to create <acronym>PIC</acronym> is
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<option>-fpic</option>. On some platforms in some situations
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<option>-fPIC</option> must be used if <option>-fpic</option>
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does not work. Refer to the GCC manual for more information.
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The compiler flag to create a shared library is
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<option>-shared</option>. A complete example looks like this:
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<programlisting>
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cc -fpic -c foo.c
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cc -shared -o foo.so foo.o
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">MacOS X</></term>
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<indexterm><primary>MacOS X</><secondary>shared library</></>
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<listitem>
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<para>
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Here is an example. It assumes the developer tools are installed.
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<programlisting>
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cc -c foo.c
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cc -bundle -flat_namespace -undefined suppress -o foo.so foo.o
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">NetBSD</></term>
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<indexterm><primary>NetBSD</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag to create <acronym>PIC</acronym> is
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<option>-fpic</option>. For <acronym>ELF</acronym> systems, the
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compiler with the flag <option>-shared</option> is used to link
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shared libraries. On the older non-ELF systems, <literal>ld
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-Bshareable</literal> is used.
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<programlisting>
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gcc -fpic -c foo.c
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gcc -shared -o foo.so foo.o
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">OpenBSD</></term>
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<indexterm><primary>OpenBSD</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag to create <acronym>PIC</acronym> is
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<option>-fpic</option>. <literal>ld -Bshareable</literal> is
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used to link shared libraries.
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<programlisting>
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gcc -fpic -c foo.c
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ld -Bshareable -o foo.so foo.o
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">Solaris</></term>
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<indexterm><primary>Solaris</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag to create <acronym>PIC</acronym> is
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<option>-KPIC</option> with the Sun compiler and
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<option>-fpic</option> with <application>GCC</>. To
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link shared libraries, the compiler option is
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<option>-G</option> with either compiler or alternatively
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<option>-shared</option> with <application>GCC</>.
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<programlisting>
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cc -KPIC -c foo.c
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cc -G -o foo.so foo.o
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</programlisting>
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or
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<programlisting>
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gcc -fpic -c foo.c
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gcc -G -o foo.so foo.o
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">Tru64 UNIX</></term>
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<indexterm><primary>Tru64 UNIX</><secondary>shared library</></>
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<indexterm><primary>Digital UNIX</><see>Tru64 UNIX</></>
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<listitem>
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<para>
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<acronym>PIC</acronym> is the default, so the compilation command
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is the usual one. <command>ld</command> with special options is
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used to do the linking:
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<programlisting>
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cc -c foo.c
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ld -shared -expect_unresolved '*' -o foo.so foo.o
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</programlisting>
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The same procedure is used with GCC instead of the system
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compiler; no special options are required.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="osname">UnixWare</></term>
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<indexterm><primary>UnixWare</><secondary>shared library</></>
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<listitem>
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<para>
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The compiler flag to create <acronym>PIC</acronym> is <option>-K
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PIC</option> with the SCO compiler and <option>-fpic</option>
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with <productname>GCC</productname>. To link shared libraries,
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the compiler option is <option>-G</option> with the SCO compiler
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and <option>-shared</option> with
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<productname>GCC</productname>.
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<programlisting>
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cc -K PIC -c foo.c
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cc -G -o foo.so foo.o
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</programlisting>
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or
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<programlisting>
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gcc -fpic -c foo.c
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gcc -shared -o foo.so foo.o
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</programlisting>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<tip>
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<para>
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If this is too complicated for you, you should consider using
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<ulink url="http://www.gnu.org/software/libtool/"><productname>GNU
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Libtool</productname></ulink>, which hides the platform differences
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behind a uniform interface.
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</para>
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</tip>
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<para>
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The resulting shared library file can then be loaded into
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<productname>PostgreSQL</productname>. When specifying the file name
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to the <command>CREATE FUNCTION</command> command, one must give it
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the name of the shared library file, not the intermediate object file.
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Note that the system's standard shared-library extension (usually
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<literal>.so</literal> or <literal>.sl</literal>) can be omitted from
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the <command>CREATE FUNCTION</command> command, and normally should
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be omitted for best portability.
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</para>
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<para>
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Refer back to <xref linkend="xfunc-c-dynload"> about where the
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server expects to find the shared library files.
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</para>
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<!--
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Under AIX, object files are compiled normally but building the shared
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library requires a couple of steps. First, create the object file:
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.nf
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cc <other flags> -c foo.c
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.fi
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You must then create a symbol \*(lqexports\*(rq file for the object
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file:
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.nf
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mkldexport foo.o `pwd` > foo.exp
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.fi
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Finally, you can create the shared library:
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.nf
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ld <other flags> -H512 -T512 -o foo.so -e _nostart \e
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-bI:.../lib/postgres.exp -bE:foo.exp foo.o \e
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-lm -lc 2>/dev/null
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.fi
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-->
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</sect2>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode:sgml
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sgml-omittag:nil
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-tabs-mode:nil
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sgml-indent-data:t
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sgml-parent-document:nil
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sgml-default-dtd-file:"./reference.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:("/usr/share/sgml/catalog")
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sgml-local-ecat-files:nil
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End:
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-->
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