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<concept id="GUID-64D2B0E2-BB5D-4009-ACE5-7A3503016341" xml:lang="en"><title>Troubleshooting
Tips</title><shortdesc>This section addresses the basic differences in the way things
are done in Symbian Platform and in Linux. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-1">       <title>Symbian
directory structure</title>       <p>In Symbian platform, project source files
are arranged based on the directory pattern shown below.</p><table id="GUID-AF9A4B8F-EC2B-4BBA-AE84-9B49F2081B4F">
<tgroup cols="2"><colspec colname="col1"/><colspec colname="col2"/>
<tbody>
<row>
<entry><p><b>Directory</b></p></entry>
<entry><p><b>Description</b></p></entry>
</row>
<row>
<entry><codeph>src</codeph></entry>
<entry><p>Contains all the source files of the project.</p></entry>
</row>
<row>
<entry><codeph>inc</codeph></entry>
<entry><p>Contains all the header files of the project.</p></entry>
</row>
<row>
<entry><codeph>group</codeph></entry>
<entry><p>Contains MMP files, and bld.inf. </p></entry>
</row>
</tbody>
</tgroup>
</table>    <p>The developer can choose whether to follow these tips.</p></section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-2">       <title>EXPORT_C,
DEF file and ordinal numbers</title>       <p>This applies only for the DLL
target type. If a DLL wants to export an API, the code definition should start
with the macro <codeph>EXPORT_C</codeph>.</p><codeblock xml:space="preserve">// Declaration
#ifdef SYMBIAN
#define GLOBAL(type)		EXPORT_C type
#else
#define GLOBAL(type)		type
#endif // SYMBIAN
 // Definition
 GLOBAL(void)
 jpeg_CreateDecompress (j_decompress_ptr cinfo, int version, size_t structsize)
 {
   int i;
 
   /* Guard against version mismatches between library and caller. */
   cinfo-&gt;mem = NULL;		/* so jpeg_destroy knows mem mgr not called */
   if (version != JPEG_LIB_VERSION)
     ERREXIT2(cinfo, JERR_BAD_LIB_VERSION, JPEG_LIB_VERSION, version);
   if (structsize != SIZEOF(struct jpeg_decompress_struct))
     ERREXIT2(cinfo, JERR_BAD_STRUCT_SIZE, 
 	     (int) SIZEOF(struct jpeg_decompress_struct), (int) structsize);
 ...
 } </codeblock><p>Whenever a DLL is built on Symbian platform, it creates
three files: </p><ul>
<li><p><filepath>&lt;target&gt;.dll</filepath> is the actual DLL that gets loaded
at runtime </p></li>
<li><p><filepath>&lt;target&gt;.lib</filepath> is the static library which contains
wrappers for each DLL exported function that, when run, will locate and execute
the real function’s code in the appropriate runtime-loaded DLL. </p></li>
<li><p><filepath>&lt;target.def&gt;</filepath> gets created when the user executes
abld freeze. The <filepath>.def</filepath> file contains the list of exported
DLL functions along with their ordinal numbers. Symbian platform does not
store exported symbol names in DLL; instead, the exported functions are referenced
using only their ordinal numbers. Storing the ordinal numbers instead of names
reduces the size of the DLL. </p></li>
</ul><p>The following is a sample <filepath>.def</filepath> file created for <codeph>libjpeg</codeph>:</p><codeblock xml:space="preserve">EXPORTS
jcopy_block_row @ 1 NONAME
jcopy_sample_rows @ 2 NONAME
jdiv_round_up @ 3 NONAME
jinit_1pass_quantizer @ 4 NONAME
jinit_2pass_quantizer @ 5 NONAME
jinit_c_coef_controller @ 6 NONAME
jinit_c_main_controller @ 7 NONAME
jinit_c_master_control @ 8 NONAME
jinit_c_prep_controller @ 9 NONAME
jinit_color_converter @ 10 NONAME
</codeblock><p>The following example shows how to declare and define an exportable
function from a DLL and to make it callable from a Symbian C++ application:
 </p><p>In <filepath>xxx.h</filepath></p><codeblock xml:space="preserve">#ifdef __cplusplus
extern "C" 
#endif
IMPORT_C int Foo();
</codeblock><p>In <codeph>xxx.c</codeph></p><codeblock xml:space="preserve">extern "C" EXPORT_C int Foo()
    {
    return something;
    }
</codeblock>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-3">       <title><codeph>dlsym()</codeph> or <codeph>g_module_symbol()</codeph></title> 
     <p>Since DLL entry points are not exported by name, DLL symbol lookup
functions do not work on Symbian platform. For more information about alternatives
suggested on Symbian platform, see <xref href="GUID-9D278187-8B5E-581D-9869-EE8861048F93.dita">Dynamic
Link Libraries</xref>.</p><p>The functions <codeph>dlsym()</codeph> from <codeph>libdl</codeph> and <codeph>g_module_symbol()</codeph> from GLib are examples of such functions. Look for usage of these functions
in the OSS port and change the code.</p><codeblock xml:space="preserve">ret = g_module_symbol (module, "jinit_c_prep_controller", &amp;ptr); 
</codeblock><p>needs to be changed to:</p><codeblock xml:space="preserve">ret = g_module_symbol (module, "9", &amp;ptr);</codeblock><p>For
example, for <codeph>dlsym()</codeph> pass the function's ordinal number as
symbol parameter (refer the library's list of exports, the DEF file for the
function's ordinal number):</p><codeblock xml:space="preserve">dlsym(&amp;handle, "foo")
</codeblock><p>needs to be changed to:</p><codeblock xml:space="preserve">dlsym (&amp;handle, "3")</codeblock></section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-4"><title>Problem with
a variable list of arguments in macros</title><p>This section suggests a way
to overcome the problems faced when macros with a variable list of arguments
are used.</p><codeblock xml:space="preserve">#define DEBUG(a,...)</codeblock><p>The above statement
causes a compilation error. One of the solutions to solve this problem is
as follows:</p><codeblock xml:space="preserve">#define DEBUG _DEBUG
static inline void _DEBUG (const char *a, ...) 
{ 
}</codeblock>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-5">       <title>Keep
changes to OSS to a minimum</title><p>While porting the OSS code, keep the
changes to the OSS code as few as possible. The OSS code is already tested
and used by a bigger community, and is unlikely to have any compilation errors
or major logical errors. In many cases code changes that are necessary brings
potential logical flaws to the OSS port. Minimum changes to the OSS code while
porting also helps in merging to the new OSS.  </p>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-6">       <title>Exporting
variables from a DLL</title>       <p>Exporting data from a DLL is not allowed
in Symbian platform . The following pattern can be used:</p><ol>
<li id="GUID-FE2ACA35-3472-47C2-8C3F-B65CAEE09C66"><p>Do not export global
variables. Within DLL, there is one global variable, for example:</p><codeblock xml:space="preserve">int globalVal; </codeblock></li>
<li id="GUID-F6A52B57-7E83-4DFE-9FD3-AB8E7D9B55D4"><p>  Export one method
that returns a pointer to that variable.</p><codeblock xml:space="preserve">extern "C" EXPORT_C int* GlbData ()
    {
    return &amp;globalVal
    }
</codeblock></li>
<li id="GUID-3231DC39-90BF-4775-BC66-2ADC9A60463E"><p>Define a macro for the
user of the DLL. See the example below. Within the DLL header (for example, <filepath>xxx.h</filepath>),
define the following:</p><codeblock xml:space="preserve">#ifdef __cplusplus
extern "C" 
#endif
IMPORT_C int* GlbData ();
#define globalVal (*GlbData())</codeblock></li>
</ol>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-7">       <title>Application
is not loaded</title>       <p>The absence of the dependent libraries could
be one of the reasons for the application not to load in the mobile device.
On the target device, Symbian platform looks for libraries in <filepath>c:\sys\bin</filepath> or
in <filepath>z:\sys\bin</filepath>.</p><p>Do make sure that all the libraries
are present in either of the above-mentioned libraries. </p>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-8">       <title>Capabilities
not known</title>       <p>Capabilities are specified in the MMP file. The
primary information source is the P.I.P.S. API reference documentation. If
problems with capabilities remain, one known method to find the capability
is to analyze the [Debug Messages] window in CodeWarrior IDE (while debugging).
During development, <codeph>CAPABILITY All –Tcb</codeph> is acceptable, but
for release code it is good practice to give a valid capability in the MMP
file in order to have the application successfully signed. The following is
a sample of a capability error found in the [Debug Messages] window.  </p><codeblock xml:space="preserve">*PlatSec* ERROR - Capability check failed - Process hellogst.exe[10015942]0001 was checked by Thread c32exe.exe[101f7989]0001::ESock_IP and was found to be missing the capabilities: NetworkServices. </codeblock>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-9">       <title>Environment
variables</title>       <p>At the moment, environment variables are not completely
supported in Symbian C++. Therefore be wary of using library functions like <codeph>getenv()</codeph> which
work on environment variables. Make sure the library initialization routine
calls <codeph>setenv()</codeph> with the proper value of the environment variable.
Also, be wary of functions like <codeph>g_get_home_dir()</codeph> which may
not work as they behave in Linux.</p><codeblock xml:space="preserve">if ((memenv = getenv("JPEGMEM")) != NULL) // will not work properly</codeblock><p>Suggested
change: </p><codeblock xml:space="preserve">void LibraryInit() 
{  
   setenv ("JPEGMEM ", "XXXXX", 1);  
}</codeblock>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-10">       <title>Assembly
code</title>       <p>The syntax for inline assembly code is different in
Symbian platform. The following is a code snippet of assembly code syntax
in Symbian platform.</p><codeblock xml:space="preserve">EXPORT_C __NAKED__ TUint16 TTemplate::Register16(TUint anAddr) 
/**  
  Read a 16-bit register  
  @returns register contents  
*/ 	
  { 	
  asm("ldrh	r0,[r0]");
  	__JUMP(,lr); 	
  } </codeblock><p>In common practice the assembly code has the extension <filepath>.CIA</filepath> in
Symbian platform, whereas in Linux the assembly code has the extension <filepath>.S</filepath>.
 </p>     </section>
<section id="GUID-77D7347D-8DEC-45D0-A677-8FDBDFB8FF81-GENID-1-7-1-11-1-1-5-1-3-1-9-1-3-11">       <title>Glossary</title> 
     <p>The following table lists terms used in Linux and their approximate
equivalents in Symbian platform:  </p><table id="GUID-BFB874F5-148B-44B2-A110-F37AC084756B">
<tgroup cols="2"><colspec colname="col1"/><colspec colname="col2"/>
<tbody>
<row>
<entry><p><b>Linux</b></p></entry>
<entry><p><b>Symbian</b></p></entry>
</row>
<row>
<entry><p><codeph>-D</codeph> of Makefile </p></entry>
<entry><p><codeph>MACRO</codeph> of theMMP file </p></entry>
</row>
<row>
<entry><p><codeph>-I</codeph> of Makefile</p></entry>
<entry><p><codeph>USERINCLUDE</codeph> of the MMP file </p></entry>
</row>
<row>
<entry><p><codeph>SO</codeph></p></entry>
<entry><p>DLL</p></entry>
</row>
<row>
<entry><p><codeph>A</codeph></p></entry>
<entry><p>LIB</p></entry>
</row>
<row>
<entry><p>Makefile</p></entry>
<entry><p>MMP file</p></entry>
</row>
<row>
<entry><p>SOURCES of Makefile </p></entry>
<entry><p>SOURCE of the MMP file </p></entry>
</row>
<row>
<entry><p><filepath>/usr/include/</filepath></p></entry>
<entry><p><filepath>\EPOC32\INCLUDE</filepath></p></entry>
</row>
<row>
<entry><p><filepath>/usr/lib/</filepath></p></entry>
<entry><p><filepath>\epoc32\data\c\sys\bin</filepath> on an emulator, <filepath>\sys\bin</filepath> on
a target device</p></entry>
</row>
</tbody>
</tgroup>
</table><p>The following table lists a few important things about the Symbian
platform: </p><table id="GUID-A43D5623-C816-4308-9AFC-FCA97DA75A2D">
<tgroup cols="2"><colspec colname="col1"/><colspec colname="col2"/>
<tbody>
<row>
<entry><p><codeph>ABI_DIR</codeph></p></entry>
<entry><p>Platform, for example winscw or armv5</p></entry>
</row>
<row>
<entry><p><codeph>BUILD_DIR</codeph></p></entry>
<entry><p>UDEB or UREL</p></entry>
</row>
<row>
<entry><p><filepath>c:</filepath> drive in emulator </p></entry>
<entry><p><filepath>\epoc32\data\c</filepath> and <filepath>\epoc32\winscw\c</filepath></p></entry>
</row>
<row>
<entry><p><filepath>z:</filepath> drive in emulator</p></entry>
<entry><p><filepath>Z:\epoc32\data\z</filepath></p></entry>
</row>
<row>
<entry><p><filepath>bld.inf</filepath></p></entry>
<entry><p>Lists public header files and their location in <filepath>\EPOC32\INCLUDE</filepath></p></entry>
</row>
</tbody>
</tgroup>
</table>     </section>
</conbody></concept>