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<concept id="GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2" xml:lang="en"><title>Standard

C++ Support on Symbian Platform</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>This topic describes the Standard C++ runtime features supported on Symbian^3. </p>

<ul>

<li id="GUID-F620B47D-35A9-54DF-89FC-031C3B3A50D4"><p><xref href="GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2.dita#GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2/GUID-B44FDC08-487F-589B-8355-CF6EAB3F25BC">Global operator new</xref>  </p> </li>

<li id="GUID-2BF296E4-1204-599D-889B-46CD0FEFCC52"><p><xref href="GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2.dita#GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2/GUID-ED64EEBA-A52D-5008-8F5F-11019BC5B1E2">new_handler</xref>  </p> </li>

<li id="GUID-E53A2527-BF8A-5578-AF29-B4E1862E958E"><p><xref href="GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2.dita#GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2/GUID-FEC1BFE6-0219-5EE8-93D1-C0D5BCFA8A26">Global object destruction</xref>  </p> </li>

<li id="GUID-303ADDE1-83D6-5449-B508-6C6DBD7DDFC9"><p><xref href="GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2.dita#GUID-2CCD1748-9EDE-5383-9941-A3051E06F3E2/GUID-1D9D2701-FD3E-57D1-952B-FB8C057FE055">STL</xref>  </p> </li>

</ul>

<section id="GUID-B44FDC08-487F-589B-8355-CF6EAB3F25BC"><title>Global operator

new</title> <p>In Standard C++, when dynamic memory allocation (using <codeph>operator

          new</codeph>) fails and if a handler is not set to handle it, the

code throws an exception (<codeph>std::bad_alloc</codeph>). But in Symbian

C++, when dynamic memory allocation fails, the code returns <b>NULL</b>. </p> <p>When

you write Standard C++ code on Symbian C++ ensure that you either use Symbian

C++ semantics of operator new or Standard C++ semantics of operator new in

your code. You can use the global <codeph>operator new</codeph> as per the

Standard C++ specification on Symbian platform by either: </p> <ul>

<li id="GUID-3E72A8F5-F68B-5454-8F20-67CC53FDC37F"><p>Building your application

or library using the STD target type. </p> </li>

<li id="GUID-40D77F25-4EE4-578A-B51E-451F7655CBA6"><p>Using the <codeph>MMP</codeph> keyword, <codeph>STDCPP</codeph>. </p> </li>

</ul> <p> <b>Note:</b> For detailed information about problems that can occur

while using the global <codeph>operator new</codeph>, see <xref href="GUID-AF2CE612-F12E-5A18-81A5-C303992D2D46.dita#GUID-AF2CE612-F12E-5A18-81A5-C303992D2D46/GUID-39350E32-26C2-5440-B221-10EE693CCF18">Use of operator new</xref>. </p> <p> <b>Warning:</b> The Symbian build system

does not permit you to mix the Standard C++ <codeph>operator new</codeph> and

the Symbian C++ <codeph>operator new</codeph>. </p> <p><b>Example</b> </p> <p>The

following example code illustrates how to use the global <codeph>operator

new</codeph> when you write Standard C++ code on Symbian platform and your

target type is a non-STD target type, for example, <codeph>exe</codeph>. </p> <p>You

must add the <codeph>MMP</codeph> keyword, <codeph>STDCPP</codeph> in the <filepath>.mmp</filepath> file

as shown in the following code: </p> <codeblock id="GUID-400432AB-79A2-5F17-9F96-22209524BC84" xml:space="preserve">//operator_new_example.mmp

Target             operator_new_example.exe

Targettype        exe

//The STDCPP keyword specifies Standard C++ 

STDCPP

Source            operator_new.cpp

Systeminclude        /epoc32/include/stdapis/stlportv5

Systeminclude        /epoc32/include/stdapis

Library            libstdcppv5.lib libc.lib

Capability        all -tcb</codeblock> <codeblock id="GUID-D3F3E4C0-D08A-5498-89A8-87A70CC02FD3" xml:space="preserve">//operator_new.cpp

#include <new>

int main()

    {

    try

        {

        int *ptr = new int(0);

        //do something

        }

    catch(std::bad_alloc)

        {

        return 1;

        }

    delete ptr;

    return 0;

    }</codeblock> </section>

<section id="GUID-ED64EEBA-A52D-5008-8F5F-11019BC5B1E2"><title>new_handler</title> <p>The

new_handler() function of Standard C++ is fully supported on Symbian platform

(the global <codeph>operator new</codeph> restrictions are applicable). You

can use the new_handler function to handle an out of memory scenario caused

by the global <codeph>operator new</codeph> when dynamic memory allocation

fails. </p> <p>The following code illustrates how to set and invoke a <codeph>new_handler</codeph>: </p> <codeblock id="GUID-E1CD4479-99AF-5547-B350-00699CD2788D" xml:space="preserve">#include &lt;new&gt;

int one_huge_chunk = 0xa000;

int *last_huge_chunk=NULL;

void foo()

    {

    /*

    * This is the new_handler and it frees the last successful allocation so

    * that the subsequent call to operator new has some free memory.

    */

    delete [] last_huge_chunk;

    }

void bar()

    {

    last_huge_chunk    = new int[one_huge_chunk];

    }

int main()

    {

    std::new_handler h_new;

    try

        {

        while(1)

            {

            // Keep allocating until we reach OOM (out of memory) condition. At OOM

            // the default new handler throws std::bad_alloc

            bar();

            }

        }

    catch(std::bad_alloc ba)

    {

    /*

    * Once the handler is set, failure of 'new' will call the handler to

    * get some free memory... 

    */

    h_new = (std::new_handler)&foo;

    try

        {

        /*

        * Try once more to see if our handler actually freed up some memory

        */

        bar();

        }

    catch(...)

        {

        }

    return 0;

    } 

    /*Failed to throw std::bad_alloc*/

    return 1;

    }</codeblock> <p> <b>Important Note:</b> The <codeph>targettype</codeph> of

this executable must either be <codeph>STDEXE</codeph> /<codeph>STDDLL</codeph> or

its <filepath>.mmp</filepath> file must use the <codeph>STDCPP</codeph> keyword. </p> </section>

<section id="GUID-FEC1BFE6-0219-5EE8-93D1-C0D5BCFA8A26"><title>Global object

destructors</title> <p>Global objects are supported both in a statically or

dynamically loaded Standard C++ DLL. Their constructors are invoked when the

DLL is loaded and their destructors are invoked when the reference count of

the DLL falls to zero. </p> <p><b>Example</b> </p> <p>The following example

illustrates the construction and destruction of a global object: </p> <codeblock id="GUID-75012329-3172-5B99-833B-24C2FB658FFF" xml:space="preserve">// glob_data.cpp

#include <iostream>

// class definition

class AClass

    {

    AClass()

        {

        std::cout << “ctor()” << std::endl; // inline constructor

        }

    ~AClass()

        {

        std::cout << “dtor()” <<std::endl; // inline destructor

        }

    };

AClass GlobData; // global instance of AClass

int main()

    {

    std::cout << “main()” << std::endl;

    }</codeblock> <p>The output of this example must be: </p> <codeblock id="GUID-0AB81D7E-B310-5CEA-86DD-65E697F4D2C2" xml:space="preserve">ctor

main

dtor</codeblock> </section>

<section id="GUID-1D9D2701-FD3E-57D1-952B-FB8C057FE055"><title>STL</title> <p>Here

are some key facts about STL support on Symbian platform: </p> <ul>

<li id="GUID-F0FCA9CA-7417-5D07-A6AA-F679B3A3A41A"><p>The Standard C++ implementation

on Symbian platform is based on STLPort version 5.1.4. </p> </li>

<li id="GUID-FB97F095-533F-582D-BD28-667D1BD6863A"><p>The Standard C++ header

files are available in the <filepath>${EPOCROOT}/epoc32/include/stdapis/stlportv5</filepath> directory. </p> </li>

<li id="GUID-F6381C75-4C30-5627-8AAA-7D8F1FF53565"><p>The Standard C++ library

name that you must use is <filepath>libstdcppv5.lib</filepath>. The value

5 (in the library name) being based on the STL Port version number, which

is 5. </p> </li>

</ul> </section>

</conbody><related-links>

<link href="GUID-D6BEAF0D-844D-51F4-8DB7-FB1D60E17FE3.dita"><linktext>Copyright

Acknowledgments for Standard C++ (STLport)</linktext></link>

<link href="GUID-F7FEB759-E64D-5B6D-9017-C5E982E4FC16.dita"><linktext>Standard

C++ Library Overview</linktext></link>

<link href="GUID-CDE8CD85-8467-5B36-A0AC-41D1D98151CA.dita"><linktext> Developing

Applications or Libraries                 Using Standard C++</linktext></link>

<link href="GUID-E331B72B-84AF-558A-9B8F-73E5E50B58C7.dita"><linktext>Building

a Standard C++ Application or Library</linktext></link>

<link href="GUID-AF2CE612-F12E-5A18-81A5-C303992D2D46.dita"><linktext>Possible

Problems</linktext></link>

<link href="GUID-5B3F5296-D6D0-5D25-8362-141DF5927E52.dita"><linktext>Troubleshooting</linktext>

</link>

<link href="GUID-D32E52C9-F05C-5F1E-8B49-243D555C353C.dita"><linktext>Known Issues</linktext>

</link>

</related-links></concept>