Mailfromd
	General-Purpose Mail Filter	Sergey Poznyakoff

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4.12.1.33 Debugging Functions

These functions allow to enable debugging and tracing for a certain piece of code.

Built-in Function: void debug (string spec)

Enable debugging. The value of spec sets the debugging level. See debugging level specification, for a description of its format.

Built-in Function: number debug_level ([string srcname])

This function returns the debugging level currently in effect for the source module srcname, or the global debugging level, if called without arguments.

For example, if the program was started with ‘--debug=20,engine=8’ option, then:

debug_level() ⇒ 20 debug_level("engine") ⇒ 8 debug_level("db") ⇒ 0

Built-in Function: string debug_spec ([string srcnames])

Returns the current debugging level specification, as given by ‘--debug’ command line option or by the debug configuration statement (see section Logging and Debugging configuration).

If the argument srcnames is specified, it is treated as a comma-separated list of source names for which the debugging specification is to be returned.

For example, if mailfromd was started with ‘--debug=20,spf=50,engine=8,db=30’ option, then:

debug_spec("all,engine") ⇒ "20,engine=8" debug_spec("engine,db") ⇒ "db=30,engine=8"

When called without arguments, debug_spec returns full debugging level specification, as shown in the example below:

debug_spec() ⇒ "20,debug=0,cache=0,dnscache=0,db=30,dns=0,dnsbase=0,engine=8, gram=0,lex=0,main=0,mf-status=0,mu_dbm=0,optab=0,prog=0, spf=50,stack=0,symtab=0,rate=0,bi_db=0,bi_dns=98,bi_io=0, bi_ipaddr=0,bi_mail=0,bi_poll=0,bi_sa=0,bi_spf=0,bi_string=7, bi_system=0,bi_other=0,bi_vars=0"

These three functions are intended to complement each other. The calls to debug can be placed around some piece of code you wish to debug, to enable specific debugging information for this code fragment only. For example:

    /* Save debugging level for ‘dns.c’ source */
    set dlev debug_level("dns")
    /* Set new debugging level */
    debug("dns=80")
    .
    .
    .
    /* Restore previous level */
    debug("dns=%dlev")

You can also change debugging levels for several modules simultaneously:

    /* Save debugging specifications for the sources we are
     * interested in:
     */
    set dspec debug_spec("dns,dnsbase,db")
    /* Set new debugging spec */
    debug("dns=80,dnsbase=100,db=1")
    .
    .
    .
    /* Restore previous debug specification */
    debug("%dspec")

Built-in Function: void program_trace (string module)

Enable tracing for a set of modules given in module argument. See –trace-program, for a description of its format.

Built-in Function: void cancel_program_trace (string module)

Disable tracing for given modules.

This pair of functions is also designed to be used together in a bracket-like fashion. They are useful for debugging mailfromd, but are not advised to use otherwise, since tracing slows down the execution considerably.

Built-in Function: void stack_trace ()

Generate a stack trace in this point. See tracing runtime errors, for the detailed description of stack traces.

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