2002-02-17 21:56:45 +00:00
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<title>libsm : Debugging and Tracing</title>
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<a href="index.html">Back to libsm overview</a>
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<center>
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<h1> libsm : Debugging and Tracing </h1>
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2002-04-20 20:31:51 +00:00
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<br> $Id: debug.html,v 1.1.1.2 2002/04/10 03:04:55 gshapiro Exp $
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2002-02-17 21:56:45 +00:00
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</center>
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<h2> Introduction </h2>
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The debug and trace package provides abstractions for writing trace
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messages, and abstractions for enabling and disabling debug and
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trace code at run time.
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<p>
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Sendmail 8.11 and earlier has a <tt>-d</tt> option which
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lets you turn on debug and trace code.
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Debug categories are integers from 0 to 99, with the sole exception
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of "ANSI", which is a named debug category.
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<p>
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The libsm debug package supports named debug categories.
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Debug category names have the form of C identifiers.
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For example, <tt>sm_trace_heap</tt> controls the output of trace
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messages from the sm heap package, while <tt>sm_check_heap</tt>
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controls the argument validity checking and memory leak detection
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features of the sm heap package.
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<p>
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In sendmail 8.12, the <tt>-d</tt> flag is generalized
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to support both the original style numeric categories, for backwards
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compatibility, and the new style named categories implemented by libsm.
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With this change,
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"-dANSI" is implemented using a libsm named debug category.
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You will be able to set a collection of named debug categories to
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the same activation level by specifying a glob pattern.
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For example,
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<dl>
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<dt>
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<tt> -dANSI </tt>
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<dd>
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sets the named category "ANSI" to level 1,
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<dt>
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<tt> -dfoo_*.3 </tt>
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<dd>
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sets all named categories matching the glob pattern "foo_*" to level 3,
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<dt>
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<tt> -d0-99.1 </tt>
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<dd>
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sets the numeric categories 0 through 99 to level 1, and
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<dt>
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<tt> -dANSI,foo_*.3,0-99.1 </tt>
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<dd>
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does all of the above.
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</dl>
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<h2> Synopsis </h2>
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<pre>
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#include <sm/debug.h>
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/*
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** abstractions for printing trace messages
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*/
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void sm_dprintf(char *fmt, ...)
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void sm_dflush()
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void sm_debug_setfile(SM_FILE_T *)
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/*
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** abstractions for setting and testing debug activation levels
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*/
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void sm_debug_addsettings(char *settings)
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void sm_debug_addsetting(char *pattern, int level)
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typedef struct sm_debug SM_DEBUG_T;
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SM_DEBUG_T dbg = SM_DEBUG_INITIALIZER("name", "@(#)$Debug: name - description $");
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bool sm_debug_active(SM_DEBUG_T *debug, int level)
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int sm_debug_level(SM_DEBUG_T *debug)
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bool sm_debug_unknown(SM_DEBUG_T *debug)
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</pre>
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<h2> Naming Conventions </h2>
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All debug categories defined by libsm have names of the form <tt>sm_*</tt>.
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Debug categories that turn on trace output have names of the form
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<tt>*_trace_*</tt>.
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Debug categories that turn on run time checks have names of the form
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<tt>*_check_*</tt>.
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Here are all of the libsm debug categories as of March 2000:
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<table>
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<tr>
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<td>Variable name</td>
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<td>Category name</td>
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<td>Meaning</td>
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</tr>
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<tr>
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<td>SmExpensiveAssert</td>
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<td>sm_check_assert</td>
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<td>enable expensive SM_ASSERT checking</td>
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</tr>
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<tr>
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<td>SmExpensiveRequire</td>
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<td>sm_check_require</td>
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<td>enable expensive SM_REQUIRE checking</td>
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</tr>
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<tr>
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<td>SmExpensiveEnsure</td>
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<td>sm_check_ensure</td>
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<td>enable expensive SM_ENSURE checking</td>
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</tr>
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<tr>
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<td>SmHeapTrace</td>
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<td>sm_trace_heap</td>
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<td>trace sm_{malloc,realloc,free} calls</td>
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</tr>
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<tr>
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<td>SmHeapCheck</td>
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<td>sm_check_heap</td>
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<td>enable checking and memory leak detection in sm_{malloc,realloc,free}</td>
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</tr>
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</table>
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<h2> Function Reference </h2>
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<dl>
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<dt>
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<tt> SM_DEBUG_INITIALIZER </tt>
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<dd>
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To create a new debug category, use the SM_DEBUG_INITIALIZER macro
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to initialize a static variable of type SM_DEBUG_T. For example,
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<blockquote><pre>
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SM_DEBUG_T ANSI_debug = SM_DEBUG_INITIALIZER("ANSI",
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"@(#)$Debug: ANSI - enable reverse video in debug output $");
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</pre></blockquote>
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There is no centralized table of category names that needs to
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be edited in order to add a new debug category.
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The sole purpose of the second argument to SM_DEBUG_INITIALIZER
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is to provide an easy way to find out what named debug categories
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are present in a sendmail binary. You can use:
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<blockquote><pre>
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ident /usr/sbin/sendmail | grep Debug
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</pre></blockquote>
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or:
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<blockquote><pre>
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what /usr/sbin/sendmail | grep Debug
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</pre></blockquote>
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<dt>
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<tt> void sm_debug_addsetting(char *pattern, int level) </tt>
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<dd>
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All debug categories default to activation level 0, which means
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no activity.
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This function updates an internal database of debug settings,
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setting all categories whose name matches the specified glob
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pattern to the specified activation level. The level argument
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must be >= 0.
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<p>
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<dt>
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<tt> void sm_debug_addsettings(char *settings) </tt>
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<dd>
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This function is used to process the <tt>-d</tt> command line
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option of Sendmail 9.x, and of other programs that support the
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setting of named debug categories. The settings argument is a
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comma-separated list of settings; each setting is a glob pattern,
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optionally followed by a '.' and a decimal numeral.
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<p>
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<dt>
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<tt> bool sm_debug_active(SM_DEBUG_T *debug, int level) </tt>
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<dd>
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This macro returns <tt>true</tt> if the activation level of
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the statically initialized debug structure <tt>debug</tt>
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is >= the specified level.
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The test is performed very efficiently: in the most common case,
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when the result is <tt>false</tt>, only a single comparison
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operation is performed.
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<p>
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This macro performs a function call only if the debug structure has
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an unknown activation level. All debug structures are in this state
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at the beginning of program execution, and after a call to
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<tt>sm_debug_addsetting</tt>.
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<p>
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<dt>
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<tt> int sm_debug_level(SM_DEBUG_T *debug) </tt>
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<dd>
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This macro returns the activation level of the specified debug structure.
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The comparison
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<blockquote><pre>
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sm_debug_level(debug) >= level
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</pre></blockquote>
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is slightly less efficient than, but otherwise semantically
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equivalent to
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<blockquote><pre>
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sm_debug_active(debug, level)
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</pre></blockquote>
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<p>
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<dt>
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<tt> bool sm_debug_unknown(SM_DEBUG_T *debug) </tt>
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<dd>
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This macro returns true if the activation level of the specified
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debug structure is unknown.
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Here is an example of how the macro might be used:
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<blockquote><pre>
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if (sm_debug_unknown(&FooDebug))
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{
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if (sm_debug_active(&FooDebug, 1))
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{
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... perform some expensive data structure initializations
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... in order to enable the "foo" debugging mechanism
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}
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else
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{
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... disable the "foo" debugging mechanism
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}
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}
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</pre></blockquote>
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The purpose of using <tt>sm_debug_unknown</tt> in the above example
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is to avoid performing the expensive initializations each time through
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the code. So it's a performance hack.
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A debug structure is in the "unknown" state at the beginning of
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program execution, and after a call to <tt>sm_debug_addsetting</tt>.
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A side effect of calling <tt>sm_debug_active</tt> is that the
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activation level becomes known.
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<p>
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<dt>
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<tt> void sm_dprintf(char *fmt, ...) </tt>
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<dd>
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This function is used to print a debug message.
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The standard idiom is
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<blockquote><pre>
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if (sm_debug_active(&BarDebug, 1))
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sm_dprintf("bar: about to test tensile strength of bar %d\n", i);
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</pre></blockquote>
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<p>
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<dt>
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<tt> void sm_dflush() </tt>
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<dd>
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Flush the debug output stream.
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<p>
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<dt>
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<tt> void sm_debug_setfile(SM_FILE_T *file) </tt>
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<dd>
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This function lets you specify where debug output is printed.
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By default, debug output is written to standard output.
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<p>
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We want to allow you to direct debug output to syslog.
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The current plan is to provide a standard interface for
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creating an SM_FILE_T object that writes to syslog.
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</dl>
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</body>
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</html>
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