glib-warnings-and-assertions.html

glid编写实例

<p>
Returns from the current function if the expression is not true.
If the expression evaluates to <code class="literal">FALSE</code>, a critical message is logged and
the function returns. This can only be used in functions which do not return
a value.
</p>
<div class="variablelist"><table border="0">
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<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>expr</code></em>&#160;:</span></td>
<td>the expression to check.


</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930232"></a><h3>
<a name="g-return-val-if-fail"></a>g_return_val_if_fail()</h3>
<a class="indexterm" name="id2930242"></a><pre class="programlisting">#define     g_return_val_if_fail(expr,val)</pre>
<p>
Returns from the current function, returning the value <em class="parameter"><code>val</code></em>, if the expression
is not true.
If the expression evaluates to <code class="literal">FALSE</code>, a critical message is logged and
<em class="parameter"><code>val</code></em> is returned.
</p>
<div class="variablelist"><table border="0">
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<tbody>
<tr>
<td>
<span class="term"><em class="parameter"><code>expr</code></em>&#160;:</span></td>
<td>the expression to check.
</td>
</tr>
<tr>
<td>
<span class="term"><em class="parameter"><code>val</code></em>&#160;:</span></td>
<td>the value to return from the current function if the expression is not
true.


</td>
</tr>
</tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930310"></a><h3>
<a name="g-return-if-reached"></a>g_return_if_reached()</h3>
<a class="indexterm" name="id2930321"></a><pre class="programlisting">#define     g_return_if_reached()</pre>
<p>
Logs a critical message and returns from the current function. 
This can only be used in functions which do not return a value.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930339"></a><h3>
<a name="g-return-val-if-reached"></a>g_return_val_if_reached()</h3>
<a class="indexterm" name="id2930350"></a><pre class="programlisting">#define     g_return_val_if_reached(val)</pre>
<p>
Logs a critical message and returns <em class="parameter"><code>val</code></em>. 
</p>
<div class="variablelist"><table border="0">
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<td>
<span class="term"><em class="parameter"><code>val</code></em>&#160;:</span></td>
<td>the value to return from the current function.


</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930389"></a><h3>
<a name="g-assert"></a>g_assert()</h3>
<a class="indexterm" name="id2930400"></a><pre class="programlisting">#define     g_assert(expr)</pre>
<p>
Debugging macro to terminate the application if the assertion fails.
If the assertion fails (i.e. the expression is not true), an error message
is logged and the application is terminated.
</p>
<p>
The macro can be turned off in final releases of code by defining
<span class="type">G_DISABLE_ASSERT</span> when compiling the application.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>expr</code></em>&#160;:</span></td>
<td>the expression to check.


</td>
</tr></tbody>
</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930451"></a><h3>
<a name="g-assert-not-reached"></a>g_assert_not_reached()</h3>
<a class="indexterm" name="id2930462"></a><pre class="programlisting">#define     g_assert_not_reached()</pre>
<p>
Debugging macro to terminate the application if it is ever reached.
If it is reached, an error message is logged and the application is terminated.
</p>
<p>
The macro can be turned off in final releases of code by defining
<span class="type">G_DISABLE_ASSERT</span> when compiling the application.
</p>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930494"></a><h3>
<a name="g-on-error-query"></a>g_on_error_query ()</h3>
<a class="indexterm" name="id2930505"></a><pre class="programlisting">void        g_on_error_query                (const <a href="glib-Basic-Types.html#gchar">gchar</a> *prg_name);</pre>
<p>
Prompts the user with <code class="computeroutput">[E]xit, [H]alt, show [S]tack trace or [P]roceed</code>.
This function is intended to be used for debugging use only. The following
example shows how it can be used together with the <a href="glib-Message-Logging.html#g-log"><code class="function">g_log()</code></a> functions.
</p>
<div class="informalexample"><pre class="programlisting">
#include &lt;glib.h&gt;

static void 
log_handler (const gchar   *log_domain,
	     GLogLevelFlags log_level,
	     const gchar   *message,
	     gpointer       user_data)
{
  g_log_default_handler (log_domain, log_level, message, user_data);

  g_on_error_query (MY_PROGRAM_NAME);
}

int main (int argc, char *argv[])
{
  g_log_set_handler (MY_LOG_DOMAIN,
		     G_LOG_LEVEL_WARNING | 
                     G_LOG_LEVEL_ERROR | 
                     G_LOG_LEVEL_CRITICAL,
		     log_handler,
		     NULL);

 /* ... */  
</pre></div>
<p>
If [E]xit is selected, the application terminates with a call to
<code class="function">_exit(0)</code>.
</p>
<p>
If [H]alt is selected, the application enters an infinite loop.
The infinite loop can only be stopped by killing the application,
or by setting <span class="type">glib_on_error_halt</span> to <code class="literal">FALSE</code> (possibly via a debugger).
</p>
<p>
If [S]tack trace is selected, <a href="glib-Warnings-and-Assertions.html#g-on-error-stack-trace"><code class="function">g_on_error_stack_trace()</code></a> is called. This
invokes <span><strong class="command">gdb</strong></span>, which attaches to the current process and shows a stack trace.
The prompt is then shown again.
</p>
<p>
If [P]roceed is selected, the function returns.
</p>
<p>
This function may cause different actions on non-UNIX platforms.
</p>
<div class="variablelist"><table border="0">
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<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>prg_name</code></em>&#160;:</span></td>
<td>the program name, needed by <span><strong class="command">gdb</strong></span> for the [S]tack trace option.
If <em class="parameter"><code>prg_name</code></em> is <code class="literal">NULL</code>, <a href="glib-Miscellaneous-Utility-Functions.html#g-get-prgname"><code class="function">g_get_prgname()</code></a> is called to get the program name
(which will work correctly if <a
href="../gdk/gdk-General.html#gdk-init"
><code class="function">gdk_init()</code></a> or <a
href="../gtk/gtk-General.html#gtk-init"
><code class="function">gtk_init()</code></a> has been called).


</td>
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</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930713"></a><h3>
<a name="g-on-error-stack-trace"></a>g_on_error_stack_trace ()</h3>
<a class="indexterm" name="id2930724"></a><pre class="programlisting">void        g_on_error_stack_trace          (const <a href="glib-Basic-Types.html#gchar">gchar</a> *prg_name);</pre>
<p>
Invokes <span><strong class="command">gdb</strong></span>, which attaches to the current process and shows a stack trace.
Called by <a href="glib-Warnings-and-Assertions.html#g-on-error-query"><code class="function">g_on_error_query()</code></a> when the [S]tack trace option is selected.
</p>
<p>
This function may cause different actions on non-UNIX platforms.
</p>
<div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody><tr>
<td>
<span class="term"><em class="parameter"><code>prg_name</code></em>&#160;:</span></td>
<td>the program name, needed by <span><strong class="command">gdb</strong></span> for the [S]tack trace option.
If <em class="parameter"><code>prg_name</code></em> is <code class="literal">NULL</code>, <a href="glib-Miscellaneous-Utility-Functions.html#g-get-prgname"><code class="function">g_get_prgname()</code></a> is called to get the program name
(which will work correctly if <a
href="../gdk/gdk-General.html#gdk-init"
><code class="function">gdk_init()</code></a> or <a
href="../gtk/gtk-General.html#gtk-init"
><code class="function">gtk_init()</code></a> has been called).


</td>
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</table></div>
</div>
<hr>
<div class="refsect2" lang="en">
<a name="id2930844"></a><h3>
<a name="G-BREAKPOINT:CAPS"></a>G_BREAKPOINT()</h3>
<a class="indexterm" name="id2930855"></a><pre class="programlisting">#define     G_BREAKPOINT()</pre>
<p>
Inserts a breakpoint instruction into the code (on x86 machines only).
</p>
</div>
</div>
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