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<P><BR></P>

<H4 ALIGN="LEFT"><A NAME="Heading13"></A><FONT COLOR="#000077">xxgdb</FONT></H4>

<P><TT>xxgdb</TT> is an X Window system-based graphical user interface to <TT>gdb</TT>. All of the features that exist in the command-line version of <TT>gdb</TT> are present in <TT>xxgdb</TT>. <TT>xxgdb</TT> enables you to perform many of the most commonly used <TT>gdb</TT> commands by pressing buttons instead of typing in commands. It also graphically represents where breakpoints have been placed.</P>

<P>Start <TT>xxgdb</TT> by typing the following into an <TT>Xterm</TT> window.</P>

<!-- CODE SNIP //-->

<PRE>

xxgdb

</PRE>

<!-- END CODE SNIP //-->

<P>When we initiate <TT>xxgdb</TT>, we can specify any of the command-line options that were available with <TT>gdb</TT>. <TT>xxgdb</TT> also has some of its own command-line options. These are described in Table 26.2.</P>

<TABLE WIDTH="100%"><CAPTION ALIGN=LEFT><B>Table 26.2.</B> The <TT>xxgdb</TT> command-line options.

<TR>

<TH COLSPAN="3"><HR>

<TR>

<TH WIDTH="15%" ALIGN="LEFT">Option

<TH WIDTH="85%" ALIGN="LEFT">Description

<TR>

<TH COLSPAN="3"><HR>

<TR>

<TD><TT>db_name</TT>

<TD>Specifies the name of the debugger to be used. The default is <TT>gdb</TT>.

<TR>

<TD><TT>db_prompt</TT>

<TD>Specifies the debugger prompt. The default is <TT>gdb</TT>.

<TR>

<TD VALIGN="TOP"><TT>gdbinit</TT>

<TD>Specifies the filename of the initial <TT>gdb</TT> command file. The default is <TT>.gdbinit</TT>.

<TR>

<TD><TT>nx</TT>

<TD>Tells <TT>xxgdb</TT> not to execute the <TT>.gdbinit</TT> file.

<TR>

<TD><TT>bigicon</TT>

<TD>Uses a large icon size for the <TT>xxgdb</TT> icon.

<TR>

<TD COLSPAN="3"><HR>

</TABLE>

<P>When you start <TT>xxgdb</TT>, a window opens on your screen. This window is shown in Figure 26.1.</P>

<P><A NAME="Fig1"></A><A HREF="javascript:displayWindow('images/26-01.jpg',554,324 )"><IMG SRC="images/26-01t.jpg"></A>

<BR><A HREF="javascript:displayWindow('images/26-01.jpg',554,324)"><FONT COLOR="#000077"><B>Figure 26.1.</B></FONT></A>&nbsp;&nbsp;The <TT>xxgdb</TT> main window.

</P>

<P>The <TT>xxgdb</TT> main window contains a message that is similar to the one displayed on the screen when the command line version of <TT>gdb</TT>is started. Near the bottom of the <TT>xxgdb</TT> main window there are four buttons. The Source Listing, Command Buttons, and Display Window buttons each bring up an additional window when they are activated. The Quit button terminates the <TT>xxgdb</TT> program.</P>

<P>The Source Listing button brings up a window that displays the source code for the program that is being debugged. This window is shown in Figure 26.2.</P>

<P><A NAME="Fig2"></A><A HREF="javascript:displayWindow('images/26-02.jpg',554,279 )"><IMG SRC="images/26-02t.jpg"></A>

<BR><A HREF="javascript:displayWindow('images/26-02.jpg',554,279)"><FONT COLOR="#000077"><B>Figure 26.2.</B></FONT></A>&nbsp;&nbsp;The <TT>xxgdb</TT> source listing window.

</P>

<P>The Command Buttons button brings up a window that contains 26 other buttons. These buttons each execute a <TT>gdb</TT> command. The <TT>gdb</TT> command-button window is illustrated in Figure 26.3.</P>

<P><A NAME="Fig3"></A><A HREF="javascript:displayWindow('images/26-03.jpg',194,389 )"><IMG SRC="images/26-03t.jpg"></A>

<BR><A HREF="javascript:displayWindow('images/26-03.jpg',194,389)"><FONT COLOR="#000077"><B>Figure 26.3.</B></FONT></A>&nbsp;&nbsp;The <TT>xxgdb</TT> command-button window.

</P>

<P>The Display Window button brings up a window that is used to display the results of any display command. You can tell <TT>xxgdb</TT> which variable or expression to display by selecting it from the source listing and then clicking on the Display button in the command-button window. The display window is illustrated in Figure 26.4.</P>

<P><A NAME="Fig4"></A><A HREF="javascript:displayWindow('images/26-04.jpg',312,129 )"><IMG SRC="images/26-04t.jpg"></A>

<BR><A HREF="javascript:displayWindow('images/26-04.jpg',312,129)"><FONT COLOR="#000077"><B>Figure 26.4.</B></FONT></A>&nbsp;&nbsp;The <TT>xxgdb</TT> display window.

</P>

<P>For more information on using <TT>xxgdb</TT>, refer to the <TT>xxgdb</TT> man page and the <TT>gdb</TT> man page.</P>

<H4 ALIGN="LEFT"><A NAME="Heading14"></A><FONT COLOR="#000077">calls</FONT></H4>

<P><TT>calls</TT> is a program that is not included on the Linux CD-ROM accompanying this book, but you can obtain a copy from the <TT>sunsite</TT> FTP site under the directory <TT>/pub/Linux/devel/lang/c/calls.tar.Z</TT>. Some older CD-ROM distributions of Linux include this file. Because it is a useful tool, we will cover it here. If you think it will be of use to you, obtain a copy from an FTP or BBS site or another CD-ROM. <TT>calls</TT> runs the GCC preprocessor on the files that are passed to it on the command line and displays a function call tree for the functions that are in those files.</P>

<BLOCKQUOTE>

<P><FONT SIZE="-1"><HR><B>Tip:&nbsp;&nbsp;</B><BR>To install <TT>calls</TT> on your system, perform the following steps while you are logged in as <TT>root</TT>:

<DL>

<DD><B>1.</B>&nbsp;&nbsp;Uncompress and <TT>untar</TT> the file.

<DD><B>2.</B>&nbsp;&nbsp;<TT>cd</TT> into the <TT>calls</TT> subdirectory that was created by the <TT>untar</TT> command.

<DD><B>3.</B>&nbsp;&nbsp;Move the file named <TT>calls</TT> to the <TT>/usr/bin</TT> directory.

<DD><B>4.</B>&nbsp;&nbsp;Move the file named <TT>calls.1</TT> to the <TT>/usr/man/man1</TT> directory.

<DD><B>5.</B>&nbsp;&nbsp;Remove the <TT>/tmp/calls</TT> directory.

</DL>

<P>This will install the <TT>calls</TT> program and man page on your system.<HR></FONT>

</BLOCKQUOTE>

</P>

<P>When <TT>calls</TT> prints out the call trace, it includes the filename in which the function is found in brackets after the function name.</P>

<!-- CODE SNIP //-->

<PRE>

main [test.c]

</PRE>

<!-- END CODE SNIP //-->

<P>If the function is not in one of the files passed to <TT>calls</TT>, it does not know where that function lives and only prints the function name.</P>

<!-- CODE SNIP //-->

<PRE>

printf

</PRE>

<!-- END CODE SNIP //-->

<P><TT>calls</TT> also makes note of recursive and static functions in its output. Recursive functions are represented in the following way:</P>

<!-- CODE SNIP //-->

<PRE>

fact &lt;&lt;&lt; recursive in factorial.c &gt;&gt;&gt;

</PRE>

<!-- END CODE SNIP //-->

<P>Static functions are represented as follows:

</P>

<!-- CODE SNIP //-->

<PRE>

total [static in calculate.c]

</PRE>

<!-- END CODE SNIP //-->

<P>As an example, assume that calls were executed with the following program as input:

</P>

<!-- CODE //-->

<PRE>

##include &lt;stdio.h&gt;



main ()

&#123;

char my_string[] = &#147;hello there&#148;;

my_print (my_string);

my_print2(my_string);

&#125;



my_print (char *string)

&#123;

printf (&#147;The string is %s\n&#148;, string);

&#125;



my_print2 (char *string)

&#123;

  char *string2;

  int size, size2, i;



  size = strlen (string);

  size2 = size -1;

  string2 = (char *) malloc (size &#43; 1);

  for (i = 0; i &lt; size; i&#43;&#43;)

    string2[size2 - i] = string[i];

  string2[size] = &#146;\0&#146;;

  printf (&#147;The string printed backward is %s\n&#148;, string2);

&#125;

</PRE>

<!-- END CODE //-->

<P>This generates the following output:

</P>

<!-- CODE SNIP //-->

<PRE>

  1 main [test.c]

  2       my_print [test.c]

  3             printf

  4       my_print2 [test.c]

  5             strlen

  6             malloc

  7             printf

</PRE>

<!-- END CODE SNIP //-->

<P><TT>calls</TT> recognizes a number of command-line options that enable you to specify the appearance of the output and which function calls get displayed. For more information on these command-line options, refer to the <TT>calls</TT> man page or enter <TT>calls -h</TT> at the command line.</P><P><BR></P>

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