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<concept id="GUID-4ADD8234-4AFD-4E80-94A4-AC018FE83276" xml:lang="en"><title>Differences
between OSS and Symbian GLib</title><shortdesc/><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>The three areas of difference between the way GLib is implemented in Symbian
platform and in OSS are as follows: </p>
<ul>
<li><p>Memory allocation</p></li>
<li><p>Spawn APIs</p></li>
<li><p>Libgmodule APIs </p></li>
</ul>
<section id="GUID-DFAD39D6-BA92-4293-B5EC-97077CE1FC1A-GENID-1-6-1-10-1-1-7-1-6-1-4-1-3-3">       <title>Memory
allocation</title>       <p>The Symbian GLib implementation does not follow
the default OSS behavior. The default OSS behavior is such that in the event
of a memory allocation failure the application, using <codeph>g_malloc()</codeph> and
not <codeph>g_try_malloc()</codeph>, will call <codeph>abort()</codeph> and
thus terminate the application.  </p><p>The Symbian implementation, on the
other hand will return NULL and not terminate the application in the event
of a memory allocation failure. Thus, it is the application’s responsibility
to check if the memory allocation failed due to the needed tasks.</p><p>Generally,
all the application code written using GLib does not perform memory allocation
failure checks. Hence, for Symbian GLib it is the application programmer's
responsibility to check for memory allocation failures.  </p>     </section>
<section id="GUID-DFAD39D6-BA92-4293-B5EC-97077CE1FC1A-GENID-1-6-1-10-1-1-7-1-6-1-4-1-3-4">       <title>Spawn
APIs</title>       <p>GLib has a set of APIs for process spawning. Since Symbian
platform does not support the <codeph>fork()</codeph> and <codeph>exec()</codeph> APIs,
the <codeph>g_spawn*</codeph> APIs have limitations in their functionality.
The limitations are explained per API in detail below.</p><p><b><codeph>g_spawn_async_with_pipes</codeph></b></p><p>The
signature of this API is:</p><codeblock xml:space="preserve">gboolean g_spawn_async_with_pipes (
    const gchar *working_directoy,
    gchar **argv,
    gchar **envp,
    GSpawnFlags flags, 			
    GSpawnChildSetupFunc child_setup, 			
    gpointer user_data, 			
    GPid *child_pid, 			
    gint  *standard_input, 			
    gint *standard_output, 			
    gint *standard_error, 			
    GError **error); </codeblock><p>This API executes the program asynchronously:
that is, the caller does not block for the spawned process to complete. The
setting of the following parameters does not have any effect in Symbian GLib:</p><ul>
<li><p><codeph>working_directory</codeph></p></li>
<li><p><codeph>envp</codeph></p></li>
</ul><p>If a value other than NULL is passed for <codeph>standard_input</codeph>, <codeph>standard_ouput</codeph>,
or <codeph>standard_error</codeph>, the value at the location is set to -1.</p><p><b><codeph>g_spawn_async</codeph></b></p><p>The
signature of the API is:</p><codeblock xml:space="preserve">gboolean g_spawn_async (
    const gchar *working_directory, 	 	  
    gchar **argv, 		  
    gchar **envp, 		  
    GSpawnFlags flags, 		  
    GSpawnChildSetupFunc child_setup, 		  
    gpointer user_data, 		  
    GPid *child_pid, 		  
    GError **error); </codeblock><p>This API calls <codeph>g_spawn_async_with_pipes</codeph> without
any pipes. The setting of the following parameters does not have any effect
in Symbian GLib:</p><ul>
<li><p><codeph>working_directory</codeph></p></li>
<li><p><codeph>envp</codeph></p></li>
</ul><p><b><codeph>g_spawn_sync</codeph></b></p><p>The signature of the API
is:</p><codeblock xml:space="preserve">gboolean g_spawn_sync(
    const gchar *working_directory, 	 	
    gchar **argv, 		
    gchar **envp, 		
    GSpawnFlags flags, 		
    GSpawnChildSetupFunc child_setup, 		
    gpointer user_data, 		
    gchar **standard_output, 		
    gchar **standard_error, 		
    gint *exit_status, 		
    GError **error); </codeblock><p>This API executes the program synchronously:
that is, the calling process waits for the spawned process to complete before
returning. The setting of the following parameters does not have any effect
on Symbian GLib:  </p><ul>
<li><p><codeph>working_directory</codeph></p></li>
<li><p><codeph>envp</codeph></p></li>
</ul><p>If a value other than NULL is passed for<codeph> standard_output</codeph> or <codeph>standard_error</codeph>,
the value at the location is set to -1. </p><p><b><codeph>g_spawn_command_line_sync</codeph></b></p><p>The
signature of the API is:</p><codeblock xml:space="preserve">gboolean g_spawn_command_line_sync(
    const gchar *command_line, 
    gchar **standard_output, 
    gchar **standard_error, 
    gint *exit_status, 
    GError **error);  </codeblock><p>This API is a simple version of <codeph>g_spawn_sync</codeph> in
which there are fewer number of parameters involved, and it takes a command
line instead.</p><p>If a value other than NULL is passed for <codeph>standard_output</codeph> or <codeph>standard_error</codeph>,
the value at the location is set to -1.</p><p>In many spawn APIs a variable
of type <codeph>GSpawnFlags</codeph> is passed. The following flags have no
effect:</p><ul>
<li><p><codeph>G_SPAWN_LEAVE_DESCRIPTORS_OPEN</codeph></p></li>
<li><p><codeph>G_SPAWN_STDOUT_TO_DEV_NULL</codeph></p></li>
<li><p><codeph>G_SPAWN_STDERR_TO_DEV_NULL</codeph></p></li>
<li><p><codeph>G_SPAWN_CHILD_INHERITS_STDIN</codeph></p></li>
</ul>     </section>
<section id="GUID-4B68F695-1BDB-4AA0-B77A-7F808A157E7A"><title>Libgmodule
APIs</title><p>Libgmodule has APIs that provide a portable method for dynamically
loading 'plug-ins' or, in other words, DLLs. There are some deviations in
the <codeph>libgmodule</codeph> APIs on Symbian platform as compared to the
OSS behavior. The APIs with their limitations are explained in detail below.</p><ul>
<li><p><b><codeph>g_module_open</codeph></b>: The signature of the API is:</p><codeblock xml:space="preserve">GModule *g_module_open (const gchar *file_name, GModuleFlags flags);</codeblock><p>This API is used to open a module. The default OSS behavior when file_name
is passed as NULL such that it obtains a <codeph>GModule</codeph> representing
the main program. In Symbian GLib, NULL is returned instead. Of all the <codeph>GModuleFlags</codeph> only <codeph>G_MODULE_BIND_LOCAL</codeph> is
honored. If the user passes any other flags, the module is still opened using
the flag <codeph>G_MODULE_BIND_LOCAL</codeph>. </p></li>
<li><p><b><codeph>g_module_symbol</codeph></b>: The signature of the API is:</p><codeblock xml:space="preserve">gboolean g_module_symbol (GModule *module, const gchar *symbol_name, gpointer *symbol);</codeblock><p>This API gets the symbol from the <codeph>GModule</codeph> opened using <codeph>g_module_open</codeph>.
In OSS, <codeph>symbol_name</codeph> is the name of the symbol that needs
to be queried from the <codeph>GModule</codeph>. In Symbian platform, the
ordinal number (passed as a string) of the symbol name must be passed and
not the symbol name.</p></li>
</ul><p>See also <xref href="GUID-01E7AE98-024C-4119-87D0-5BB9D53DA119.dita">Introduction
to libgmodule</xref> for more details about <codeph>libgmodule</codeph>. </p></section>
</conbody></concept>