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+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 4. The samba DEBUG system</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt02.html" title="Part II. Samba Basics"><link rel="prev" href="architecture.html" title="Chapter 3. Samba Architecture"><link rel="next" href="internals.html" title="Chapter 5. Samba Internals"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 4. The samba DEBUG system</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="architecture.html">Prev</a> </td><th width="60%" align="center">Part II. Samba Basics</th><td width="20%" align="right"> <a accesskey="n" href="internals.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="debug"></a>Chapter 4. The samba DEBUG system</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Chris</span> <span class="surname">Hertel</span></h3></div></div><div><p class="pubdate">July 1998</p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="debug.html#id2523090">New Output Syntax</a></span></dt><dt><span class="sect1"><a href="debug.html#id2523209">The DEBUG() Macro</a></span></dt><dt><span class="sect1"><a href="debug.html#id2523318">The DEBUGADD() Macro</a></span></dt><dt><span class="sect1"><a href="debug.html#id2523355">The DEBUGLVL() Macro</a></span></dt><dt><span class="sect1"><a href="debug.html#id2523448">New Functions</a></span></dt><dd><dl><dt><span class="sect2"><a href="debug.html#id2523454">dbgtext()</a></span></dt><dt><span class="sect2"><a href="debug.html#id2523470">dbghdr()</a></span></dt><dt><span class="sect2"><a href="debug.html#id2523490">format_debug_text()</a></span></dt></dl></dd></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523090"></a>New Output Syntax</h2></div></div></div><p>
+ The syntax of a debugging log file is represented as:
+</p><pre class="programlisting">
+ >debugfile< :== { >debugmsg< }
+
+ >debugmsg< :== >debughdr< '\n' >debugtext<
+
+ >debughdr< :== '[' TIME ',' LEVEL ']' FILE ':' [FUNCTION] '(' LINE ')'
+
+ >debugtext< :== { >debugline< }
+
+ >debugline< :== TEXT '\n'
+</pre><p>
+TEXT is a string of characters excluding the newline character.
+</p><p>
+LEVEL is the DEBUG level of the message (an integer in the range
+ 0..10).
+</p><p>
+TIME is a timestamp.
+</p><p>
+FILE is the name of the file from which the debug message was
+generated.
+</p><p>
+FUNCTION is the function from which the debug message was generated.
+</p><p>
+LINE is the line number of the debug statement that generated the
+message.
+</p><p>Basically, what that all means is:</p><div class="orderedlist"><ol type="1"><li><p>
+A debugging log file is made up of debug messages.
+</p></li><li><p>
+Each debug message is made up of a header and text. The header is
+separated from the text by a newline.
+</p></li><li><p>
+The header begins with the timestamp and debug level of the
+message enclosed in brackets. The filename, function, and line
+number at which the message was generated follow. The filename is
+terminated by a colon, and the function name is terminated by the
+parenthesis which contain the line number. Depending upon the
+compiler, the function name may be missing (it is generated by the
+__FUNCTION__ macro, which is not universally implemented, dangit).
+</p></li><li><p>
+The message text is made up of zero or more lines, each terminated
+by a newline.
+</p></li></ol></div><p>Here's some example output:</p><pre class="programlisting">
+ [1998/08/03 12:55:25, 1] nmbd.c:(659)
+ Netbios nameserver version 1.9.19-prealpha started.
+ Copyright Andrew Tridgell 1994-1997
+ [1998/08/03 12:55:25, 3] loadparm.c:(763)
+ Initializing global parameters
+</pre><p>
+Note that in the above example the function names are not listed on
+the header line. That's because the example above was generated on an
+SGI Indy, and the SGI compiler doesn't support the __FUNCTION__ macro.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523209"></a>The DEBUG() Macro</h2></div></div></div><p>
+Use of the DEBUG() macro is unchanged. DEBUG() takes two parameters.
+The first is the message level, the second is the body of a function
+call to the Debug1() function.
+</p><p>That's confusing.</p><p>Here's an example which may help a bit. If you would write</p><pre class="programlisting">
+printf( "This is a %s message.\n", "debug" );
+</pre><p>
+to send the output to stdout, then you would write
+</p><pre class="programlisting">
+DEBUG( 0, ( "This is a %s message.\n", "debug" ) );
+</pre><p>
+to send the output to the debug file. All of the normal printf()
+formatting escapes work.
+</p><p>
+Note that in the above example the DEBUG message level is set to 0.
+Messages at level 0 always print. Basically, if the message level is
+less than or equal to the global value DEBUGLEVEL, then the DEBUG
+statement is processed.
+</p><p>
+The output of the above example would be something like:
+</p><pre class="programlisting">
+ [1998/07/30 16:00:51, 0] file.c:function(128)
+ This is a debug message.
+</pre><p>
+Each call to DEBUG() creates a new header *unless* the output produced
+by the previous call to DEBUG() did not end with a '\n'. Output to the
+debug file is passed through a formatting buffer which is flushed
+every time a newline is encountered. If the buffer is not empty when
+DEBUG() is called, the new input is simply appended.
+</p><p>
+...but that's really just a Kludge. It was put in place because
+DEBUG() has been used to write partial lines. Here's a simple (dumb)
+example of the kind of thing I'm talking about:
+</p><pre class="programlisting">
+ DEBUG( 0, ("The test returned " ) );
+ if( test() )
+ DEBUG(0, ("True") );
+ else
+ DEBUG(0, ("False") );
+ DEBUG(0, (".\n") );
+</pre><p>
+Without the format buffer, the output (assuming test() returned true)
+would look like this:
+</p><pre class="programlisting">
+ [1998/07/30 16:00:51, 0] file.c:function(256)
+ The test returned
+ [1998/07/30 16:00:51, 0] file.c:function(258)
+ True
+ [1998/07/30 16:00:51, 0] file.c:function(261)
+ .
+</pre><p>Which isn't much use. The format buffer kludge fixes this problem.
+</p></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523318"></a>The DEBUGADD() Macro</h2></div></div></div><p>
+In addition to the kludgey solution to the broken line problem
+described above, there is a clean solution. The DEBUGADD() macro never
+generates a header. It will append new text to the current debug
+message even if the format buffer is empty. The syntax of the
+DEBUGADD() macro is the same as that of the DEBUG() macro.
+</p><pre class="programlisting">
+ DEBUG( 0, ("This is the first line.\n" ) );
+ DEBUGADD( 0, ("This is the second line.\nThis is the third line.\n" ) );
+</pre><p>Produces</p><pre class="programlisting">
+ [1998/07/30 16:00:51, 0] file.c:function(512)
+ This is the first line.
+ This is the second line.
+ This is the third line.
+</pre></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523355"></a>The DEBUGLVL() Macro</h2></div></div></div><p>
+One of the problems with the DEBUG() macro was that DEBUG() lines
+tended to get a bit long. Consider this example from
+nmbd_sendannounce.c:
+</p><pre class="programlisting">
+ DEBUG(3,("send_local_master_announcement: type %x for name %s on subnet %s for workgroup %s\n",
+ type, global_myname, subrec->subnet_name, work->work_group));
+</pre><p>
+One solution to this is to break it down using DEBUG() and DEBUGADD(),
+as follows:
+</p><pre class="programlisting">
+ DEBUG( 3, ( "send_local_master_announcement: " ) );
+ DEBUGADD( 3, ( "type %x for name %s ", type, global_myname ) );
+ DEBUGADD( 3, ( "on subnet %s ", subrec->subnet_name ) );
+ DEBUGADD( 3, ( "for workgroup %s\n", work->work_group ) );
+</pre><p>
+A similar, but arguably nicer approach is to use the DEBUGLVL() macro.
+This macro returns True if the message level is less than or equal to
+the global DEBUGLEVEL value, so:
+</p><pre class="programlisting">
+ if( DEBUGLVL( 3 ) )
+ {
+ dbgtext( "send_local_master_announcement: " );
+ dbgtext( "type %x for name %s ", type, global_myname );
+ dbgtext( "on subnet %s ", subrec->subnet_name );
+ dbgtext( "for workgroup %s\n", work->work_group );
+ }
+</pre><p>(The dbgtext() function is explained below.)</p><p>There are a few advantages to this scheme:</p><div class="orderedlist"><ol type="1"><li><p>
+The test is performed only once.
+</p></li><li><p>
+You can allocate variables off of the stack that will only be used
+within the DEBUGLVL() block.
+</p></li><li><p>
+Processing that is only relevant to debug output can be contained
+within the DEBUGLVL() block.
+</p></li></ol></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2523448"></a>New Functions</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523454"></a>dbgtext()</h3></div></div></div><p>
+This function prints debug message text to the debug file (and
+possibly to syslog) via the format buffer. The function uses a
+variable argument list just like printf() or Debug1(). The
+input is printed into a buffer using the vslprintf() function,
+and then passed to format_debug_text().
+
+If you use DEBUGLVL() you will probably print the body of the
+message using dbgtext().
+</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523470"></a>dbghdr()</h3></div></div></div><p>
+This is the function that writes a debug message header.
+Headers are not processed via the format buffer. Also note that
+if the format buffer is not empty, a call to dbghdr() will not
+produce any output. See the comments in dbghdr() for more info.
+</p><p>
+It is not likely that this function will be called directly. It
+is used by DEBUG() and DEBUGADD().
+</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2523490"></a>format_debug_text()</h3></div></div></div><p>
+This is a static function in debug.c. It stores the output text
+for the body of the message in a buffer until it encounters a
+newline. When the newline character is found, the buffer is
+written to the debug file via the Debug1() function, and the
+buffer is reset. This allows us to add the indentation at the
+beginning of each line of the message body, and also ensures
+that the output is written a line at a time (which cleans up
+syslog output).
+</p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="architecture.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="internals.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 3. Samba Architecture </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 5. Samba Internals</td></tr></table></div></body></html>
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