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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->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 &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>