Author: wyoung
Date: Mon Dec 3 16:59:49 2007
New Revision: 1968
URL: http://svn.gna.org/viewcvs/mysqlpp?rev=1968&view=rev
Log:
Expanded new section on SSQLS in multiple modules
Modified:
trunk/doc/userman/userman.dbx
Modified: trunk/doc/userman/userman.dbx
URL:
http://svn.gna.org/viewcvs/mysqlpp/trunk/doc/userman/userman.dbx?rev=1968&r1=1967&r2=1968&view=diff
==============================================================================
--- trunk/doc/userman/userman.dbx (original)
+++ trunk/doc/userman/userman.dbx Mon Dec 3 16:59:49 2007
@@ -286,7 +286,7 @@
any other structure. The results can be accessed through
the Row object, or you can ask the library to dump the
results into an STL container — sequential or
- set-associative, it doesn't matter —
+ set-associative, it doesn't matter —
for you. Consider this:</para>
<programlisting>
@@ -299,9 +299,9 @@
<para>Isn't that slick?</para>
- <para>If you don't want to create SSQLSes to match your
- table structures, as of MySQL++ v3 you can now use
- <classname>Row</classname> here instead:</para>
+ <para>If you don't want to create SSQLSes to match your
+ table structures, as of MySQL++ v3 you can now use
+ <classname>Row</classname> here instead:</para>
<programlisting>
vector<mysqlpp::Row> v;
@@ -311,8 +311,8 @@
cout << "Price: " << it->at("price") << endl;
}</programlisting>
- <para>It lacks a certain syntactic elegance, but it has
its
- uses.</para>
+ <para>It lacks a certain syntactic elegance, but it has its
+ uses.</para>
</sect3>
</sect2>
@@ -1920,33 +1920,59 @@
one module, you get a multiply-defined symbol error at link
time.</para>
- <para>The way around this is to add this before <emphasis>all
- but one</emphasis> of the places where you pull in the header
- definining the SSQLS:</para>
-
- <programlisting>
-#define MYSQLPP_SSQLS_NO_STATICS</programlisting>
-
- <para>This suppresses the static data members in any SSQLS
- defined thereafter.</para>
-
- <para>These data members must exist, so one (and only
- one!) module must bring in the SSQLS definition without
- this being defined. Thus, you don't want to put this
- <userinput>#define</userinput> in the header file with the
- SSQLS definition. It's usually easy to find one module in a
- program that logically "owns" each SSQLS, and it can pull in
- the header definining the SSQLS directly, without suppressing
- the static data members.</para>
-
- <para>Note that due to a compiler limitation, you can't
- use this feature with Visual C++ 2003. As instructed
- in <filename>README.vc</filename>, you have to disable
- this feature in order to get the SSQLS header files to
- compile. Having done that, the SSQLS feature works fine as
- long as you can live with using each structure type in a
- single module. Visual C++ 2005 and newer don't suffer from
- this limitation.</para>
+ <para>The way around this is to define the preprocessor macro
+ <varname>MYSQLPP_SSQLS_NO_STATICS</varname> in <emphasis>all
+ but one</emphasis> of the modules that use the header
+ definining the SSQLS. When this macro is defined, it suppresses
+ the static data members in any SSQLS defined thereaftear.</para>
+
+ <para>Imagine we have a file <filename>my_ssqls.h</filename>
+ which includes a <function>sql_create_N</function> macro call
+ to define an SSQLS, and that that SSQLS is used in at least
+ two modules. One we'll call <filename>foo.cpp</filename>,
+ and we'll say it's just a user of the SSQLS; it doesn't "own"
+ it. Another of the modules, <filename>my_ssqls.cpp</filename>
+ uses the SSQLS more heavily, so we've called it the owner
+ of the SSQLS. If there aren't very many modules, this works
+ nicely:</para>
+
+ <programlisting>
+// File foo.cpp, which just uses the SSQLS, but doesn't "own" it:
+#define MYSQLPP_SSQLS_NO_STATICS
+#include "my_ssqls.h"</programlisting>
+
+ <programlisting>
+// File my_ssqls.cpp, which owns the SSQLS, so we just #include it directly
+#include "my_ssqls.h"</programlisting>
+
+ <para>If there are many modules that need the SSQLS, adding all
+ those <command>#defines</command> can be a pain. In that case,
+ it's easier if you flip the above pattern on its head:</para>
+
+ <programlisting>
+// File my_ssqls.h:
+#if !defined(EXPAND_MY_SSQLS_STATICS)
+# define MYSQLPP_SSQLS_NO_STATICS
+#endif
+sql_create_X(Y, Z....) // the SSQLS definition</programlisting>
+
+ <programlisting>
+// File foo.cpp, a mere user of the SSQLS:
+#include "my_ssqls.h"</programlisting>
+
+ <programlisting>
+// File my_ssqls.cpp, which owns the SSQLS:
+#define EXPAND_MY_SSQLS_STATICS
+#include "my_ssqls.h"</programlisting>
+
+ <para>Note that due to a compiler limitation, you can't use the
+ <varname>MYSQLPP_SSQLS_NO_STATICS</varname> feature with Visual
+ C++ 2003. As instructed in <filename>README.vc</filename>,
+ you have to disable this feature in order to get the SSQLS
+ header files to compile. Having done that, the SSQLS feature
+ works fine as long as you can live with using each structure
+ type in a single module. Visual C++ 2005 and newer don't
+ suffer from this limitation.</para>
</sect2>
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