From 8f8a9f01909ba29e2b781310baeeaaddc3f15f0d Mon Sep 17 00:00:00 2001 From: "Gerald W. Carter" Date: Tue, 22 Apr 2008 10:09:40 -0500 Subject: Moving docs tree to docs-xml to make room for generated docs in the release tarball. (This used to be commit 9f672c26d63955f613088489c6efbdc08b5b2d14) --- docs-xml/Samba3-Developers-Guide/debug.xml | 323 +++++++++++++++++++++++++++++ 1 file changed, 323 insertions(+) create mode 100644 docs-xml/Samba3-Developers-Guide/debug.xml (limited to 'docs-xml/Samba3-Developers-Guide/debug.xml') diff --git a/docs-xml/Samba3-Developers-Guide/debug.xml b/docs-xml/Samba3-Developers-Guide/debug.xml new file mode 100644 index 0000000000..a55facedff --- /dev/null +++ b/docs-xml/Samba3-Developers-Guide/debug.xml @@ -0,0 +1,323 @@ + + + + + + ChrisHertel + + July 1998 + + +The samba DEBUG system + + +New Output Syntax + + + The syntax of a debugging log file is represented as: + + + + >debugfile< :== { >debugmsg< } + + >debugmsg< :== >debughdr< '\n' >debugtext< + + >debughdr< :== '[' TIME ',' LEVEL ']' FILE ':' [FUNCTION] '(' LINE ')' + + >debugtext< :== { >debugline< } + + >debugline< :== TEXT '\n' + + + +TEXT is a string of characters excluding the newline character. + + + +LEVEL is the DEBUG level of the message (an integer in the range + 0..10). + + + +TIME is a timestamp. + + + +FILE is the name of the file from which the debug message was +generated. + + + +FUNCTION is the function from which the debug message was generated. + + + +LINE is the line number of the debug statement that generated the +message. + + +Basically, what that all means is: + + +A debugging log file is made up of debug messages. + + +Each debug message is made up of a header and text. The header is +separated from the text by a newline. + + +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). + + +The message text is made up of zero or more lines, each terminated +by a newline. + + + +Here's some example output: + + + [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 + + + +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. + + + + + +The DEBUG() Macro + + +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. + + +That's confusing. + +Here's an example which may help a bit. If you would write + + +printf( "This is a %s message.\n", "debug" ); + + + +to send the output to stdout, then you would write + + + +DEBUG( 0, ( "This is a %s message.\n", "debug" ) ); + + + +to send the output to the debug file. All of the normal printf() +formatting escapes work. + + + +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. + + + +The output of the above example would be something like: + + + + [1998/07/30 16:00:51, 0] file.c:function(128) + This is a debug message. + + + +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. + + + +...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: + + + + DEBUG( 0, ("The test returned " ) ); + if( test() ) + DEBUG(0, ("True") ); + else + DEBUG(0, ("False") ); + DEBUG(0, (".\n") ); + + + +Without the format buffer, the output (assuming test() returned true) +would look like this: + + + + [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) + . + + +Which isn't much use. The format buffer kludge fixes this problem. + + + + + +The DEBUGADD() Macro + + +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. + + + + DEBUG( 0, ("This is the first line.\n" ) ); + DEBUGADD( 0, ("This is the second line.\nThis is the third line.\n" ) ); + + +Produces + + + [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. + + + + + +The DEBUGLVL() Macro + + +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: + + + + 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)); + + + +One solution to this is to break it down using DEBUG() and DEBUGADD(), +as follows: + + + + 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 ) ); + + + +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: + + + + 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 ); + } + + +(The dbgtext() function is explained below.) + +There are a few advantages to this scheme: + + +The test is performed only once. + + +You can allocate variables off of the stack that will only be used +within the DEBUGLVL() block. + + +Processing that is only relevant to debug output can be contained +within the DEBUGLVL() block. + + + + + + +New Functions + + +dbgtext() + +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(). + + + + +dbghdr() + +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. + + + +It is not likely that this function will be called directly. It +is used by DEBUG() and DEBUGADD(). + + + + +format_debug_text() + +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). + + + + -- cgit