Sweden-Number/documentation/debugging.sgml

  <chapter id="debugging">
    <title>Debug Logging</title>

      <para>
        Written by &name-dimitrie-paun; <email>&email-dimitrie-paun;</email>, 28 Mar 1998
      </para>
      <para>
        (Extracted from <filename>wine/documentation/debug-msgs</filename>)
      </para>

      <note>
        <para>
          The new debugging interface can be considered to be
          stable, with the exception of the in-memory message
          construction functions. However, there is still a lot of
          work to be done to polish things up. To make my life
          easier, please follow the guidelines described in this
          document. 
        </para>
      </note>

      <important>
        <para>
          Read this document before writing new code. DO NOT USE
          <function>fprintf</function>  (or
          <function>printf</function>) to output things. Also, instead
          of writing  FIXMEs in the source, output a FIXME message if
          you can. 
        </para>
        <para>
          At the end of the document, there is a "Style Guide" for
          debugging messages. Please read it.
        </para>
      </important>

      <sect1 id="dbg-classes">
        <title>Debugging classes</title>

        <para>
          There are 4 types (or classes) of debugging messages:
        </para>
        <variablelist>
          <varlistentry>
            <term><literal>FIXME</literal></term>
            <listitem>
              <para>
                Messages in this class relate to behavior of Wine that
                does not correspond to standard Windows behavior and
                that should be fixed. 
              </para>
              <para>Examples: stubs, semi-implemented features, etc.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>ERR</literal></term>
            <listitem>
              <para>
                Messages in this class relate to serious errors in
                Wine. This sort of messages are close to asserts --
                that is, you should output an error message when the
                code detects a condition which should not happen. In
                other words, important things that are not warnings
                (see below), are errors. 
              </para>
              <para>
                Examples: unexpected change in internal state, etc.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>WARN</literal></term>
            <listitem>
              <para>
                These are warning messages. You should report a
                warning when something unwanted happen but the
                function behaves properly. That is, output a warning
                when you encounter something unexpected (ex: could not
                open a file) but the function deals correctly with the
                situation (that is, according to the docs). If you do
                not deal correctly with it, output a fixme. 
              </para>
              <para>
                Examples: fail to access a resource required by the
                app, etc.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term><literal>TRACE</literal></term>
            <listitem>
              <para>
                These are detailed debugging messages that are mainly
                useful  to debug a component. These are usually turned
                off.
              </para>
              <para>
                Examples: everything else that does not fall in one of
                the above mentioned categories and the user does not
                need to know about it.
              </para>
            </listitem>
          </varlistentry>
        </variablelist>

        <para>
          The user has the capability to turn on or off messages of a
          particular type. You can expect the following patterns of
          usage (but note that  any combination is possible):
        </para>
        <itemizedlist>
          <listitem>
            <para>
              when you debug a component, all types
              (<literal>TRACE</literal>, <literal>WARN</literal>,
              <literal>ERR</literal>, <literal>FIXME</literal>) will
              be enabled.
            </para>
          </listitem>
          <listitem>
            <para>
              during the pre-alpha (maybe alpha) stage of Wine, most
              likely the <literal>TRACE</literal> class will be
              disabled by default, but all others
              (<literal>WARN</literal>, <literal>ERR</literal>,
              <literal>FIXME</literal>) will be enabled by default.
            </para>
          </listitem>
          <listitem>
            <para>
              when Wine will become stable, most likely the
              <literal>TRACE</literal> and <literal>WARN</literal>
              classes will be disabled by default, but all
              <literal>ERR</literal>s and <literal>FIXME</literal>s
              will be enabled.
            </para>
          </listitem>
          <listitem>
            <para>
              in some installations that want the smallest footprint
              and where the debug information is of no interest,  all
              classes may be disabled by default.
            </para>
          </listitem>
        </itemizedlist>
        <para>
          Of course, the user will have the runtime ability to
          override these defaults. However, this ability may be turned
          off and certain classes of messages may be completely
          disabled at compile time to reduce the  size of Wine.
        </para>
      </sect1>

      <sect1 id="dbg-channels">
        <title>Debugging channels</title>

        <para>
          Also, we divide the debugging messages on a component basis.
          Each component is assigned a debugging channel. The
          identifier of the channel must be a valid C identifier but
          note that it may also be a reserved word like
          <type>int</type> or <type>static</type>.
        </para>
        <para>
          Examples of debugging channels:
          <simplelist type="inline">
            <member><literal>reg</literal></member>
            <member><literal>updown</literal></member>
            <member><literal>string</literal></member>
          </simplelist>
        </para>
        <para>
          We will refer to a generic channel as <literal>xxx</literal>.
        </para>
        <note>
          <para>
            for those who know the old interface, the channel/type is
            what followed the _ in the
            <function>dprintf_xxx</function> statements. For example,
            to output a message on the debugging channel
            <literal>reg</literal> in the old interface you would had
            to write:
          </para>
          <programlisting>
dprintf_reg(stddeb, "Could not access key!\n");
          </programlisting>
          <para>
            In the new interface, we drop the
            <literal>stddeb</literal> as it is implicit. However, we
            add an orthogonal piece of information to the message: its
            class. This is very important as it will allow us to
            selectively turn on or off certain messages based on the
            type of information they report. For this reason it is
            essential to choose the right class for the message.
            Anyhow, suppose we figured that this message should belong
            in the <literal>WARN</literal> class, so in the new
            interface, you write:
          </para>
          <programlisting>
WARN(reg, "Could not access key!\n");
          </programlisting>
        </note>
      </sect1>

      <sect1 id="dbg-using">
        <title>How to use it</title>

        <para>
          So, to output a message (class <literal>YYY</literal>) on
          channel <literal>xxx</literal>, do:
        </para>
        <programlisting>
#include "debugtools.h"

....

YYY(xxx, "&lt;message>", ...);
        </programlisting>
        <para>
          Some examples from the code:
        </para>
        <programlisting>
#include "debugtools.h"

...

  TRACE(crtdll, "CRTDLL_setbuf(file %p buf %p)", file, buf);

  WARN(aspi, "Error opening device errno=%d", save_error);
        </programlisting>
        <para>
          If you need to declare a new debugging channel, use it in
          your code and then do:
        </para>
        <screen>
%tools/make_debug
        </screen>
        <para>
          in the root directory of Wine. Note that this will result in
          almost complete recompilation of Wine.
        </para>

        <note>
          <orderedlist>
            <listitem>
              <para>
                Please pay attention to which class you assign the
                message. There are only 4 classes, so it is not hard.
                The reason it is important to get it right is that too
                much information is no information. For example, if
                you put things into the <literal>WARN</literal> class
                that should really be in the <literal>TRACE</literal>
                class, the  output will be too big and this will force
                the user to  turn warnings off. But this way he will
                fail to see the important ones. Also, if you put
                warnings into the <literal>TRACE</literal> class lets
                say, he will most likely miss those because usually
                the <literal>TRACE</literal> class is turned off. A
                similar argument can be made if you mix any other two
                classes.
              </para>
            </listitem>
            <listitem>
              <para>
                All lines should end with a newline. If you can NOT
                output everything that you want in the line with only
                one statement, then you need to build the string in
                memory. Please read the section below "In-memory
                messages" on the preferred way to do it. PLEASE USE
                THAT INTERFACE TO BUILD MESSAGES IN MEMORY. The reason
                is that we are not sure that we like it and having
                everything in one format will facilitate the
                (automatic) translation to a better interface.
              </para>
            </listitem>
          </orderedlist>
        </note>
      </sect1>

      <sect1 id="dbg-checking">
        <title>Are we debugging?</title>

        <para>
          To test whether the debugging output of class
          <literal>yyy</literal> on channel <literal>xxx</literal> is
          enabled, use:
        </para>
        <screen>
TRACE_ON  to test if TRACE is enabled
WARN_ON   to test if WARN is enabled
FIXME_ON  to test if FIXME is enabled
ERR_ON    to test if ERR is enabled
        </screen>
        <para>
          Examples:
        </para>
        <programlisting>
if(TRACE_ON(atom)){
  ...blah...
}
        </programlisting>

        <note>
          <para>
            You should normally need to test only if
            <literal>TRACE_ON</literal>. At present, none of the other
            3 tests (except for <literal>ERR_ON</literal> which is
            used only once!) are used in Wine.
          </para>
        </note>
      </sect1>

      <sect1 id="dbg-in-memory">
        <title>In-memory messages</title>

        <para>
          If you NEED to build the message from multiple calls, you
          need to  build it in memory. To do that, you should use the
          following interface:
        </para>

        <orderedlist>
          <listitem>
            <para>
              declare a string (where you are allowed to declare C
              variables) as follows:
            <programlisting>
dbg_decl_str(name, len);
            </programlisting>
              where <parameter>name</parameter> is the name of the
              string (you should use the channel name on which you
              are going to output it)
            </para>
          </listitem>
          <listitem>
            <para>
              print in it with:
            <programlisting>
dsprintf(name, "&lt;message>", ...);
            </programlisting>
              which is just like a <function>sprintf</function>
              function but instead of a C string as first parameter it
              takes the name you used to declare it.
            </para>
          </listitem>
          <listitem>
            <para>
              obtain a pointer to the string with: <function>dbg_str(name)</function>
            </para>
          </listitem>
          <listitem>
            <para>
              reset the string (if you want to reuse it with):
              <programlisting>
dbg_reset_str(name);
              </programlisting>
            </para>
          </listitem>
        </orderedlist>

        <para>
          Example (modified from the code):
        </para>
        <programlisting>
void some_func(tabs)
{
  INT32 i;
  LPINT16 p = (LPINT16)tabs;
  dbg_decl_str(listbox, 256);                   /* declare the string */

  for (i = 0; i &lt; descr->nb_tabs; i++) {
    descr->tabs[i] = *p++&lt;&lt;1; 
    if(TRACING(listbox))                         /* write in it only if
      dsprintf(listbox, "%hd ", descr->tabs[i]); /* we are gonna output it */
  }
  TRACE(listbox, "Listbox %04x: settabstops %s", 
	wnd->hwndSelf, dbg_str(listbox));        /* output the whole thing */
}
        </programlisting>
        <para>
          If you need to use it two times in the same scope do like
          this:
        </para>
        <programlisting>
void some_func(tabs)
{
  INT32 i;
  LPINT16 p = (LPINT16)tabs;
  dbg_decl_str(listbox, 256);                   /* declare the string      */

  for (i = 0; i &lt; descr->nb_tabs; i++) {
    descr->tabs[i] = *p++&lt;&lt;1;  
    if(TRACING(listbox))                         /* write in it only if
      dsprintf(listbox, "%hd ", descr->tabs[i]); /* we are gonna output it */
  }
  TRACE(listbox, "Listbox %04x: settabstops %s\n", 
	wnd->hwndSelf, dbg_str(listbox));        /* output the whole thing */

  dbg_reset_str(listbox);                        /* !!!reset the string!!! */
  for (i = 0; i &lt; descr->extrainfo_nr; i++) {
    descr->extrainfo = *p+1; 
    if(TRACING(listbox))                         /* write in it only if
      dsprintf(listbox,"%3d ",descr->extrainfo); /* we are gonna output it */
  }

  TRACE(listbox, "Listbox %04x: extrainfo %s\n", 
	wnd->hwndSelf, dbg_str(listbox));        /* output the whole thing */

}
        </programlisting>

        <important>
          <para>
            As I already stated, I do not think this will be the
            ultimate interface for building in-memory debugging
            messages. In fact, I do have better ideas which I hope to
            have time to implement for the next release. For this
            reason, please try not to use it. However, if you need to
            output a line in more than one
            <function>dprintf_xxx</function> calls, then USE THIS
            INTERFACE. DO NOT use other methods. This way, I will
            easily translate everything to the new interface (when it
            will become available). So, if you need to use it, then
            follow the following guidelines:
          </para>
          <itemizedlist>
            <listitem>
              <para>wrap calls to <function>dsprintf</function> with a
              </para>
              <programlisting>
if(YYY(xxx))
  dsprintf(xxx,...);
              </programlisting>
              <para>
                Of course, if the call to
                <function>dsprintf</function> is made from within a
                function  which you know is called only if
                <function>YYY(xxx)</function> is true, for example if
                you call it only like this:
              </para>
              <programlisting>
if(YYY(xxx))
  print_some_debug_info();
              </programlisting>
              <para>
                then you need not (and should not) wrap calls to
                <function>dsprintf</function> with the before
                mentioned <function>if</function>.
              </para>
            </listitem>
            <listitem>
              <para>
                name the string EXACTLY like the debugging channel on
                which is going to be output. Please see the above
                example. 
              </para>
            </listitem>
          </itemizedlist>
        </important>
      </sect1>

      <sect1 id="dbg-resource-ids">
        <title>Resource identifiers</title>

        <para>
          Resource identifiers can be either strings or numbers. To
          make life a bit easier for outputting these beasts (and to
          help you avoid the need to build the message in memory), I
          introduced a new function called <function>debugres</function>.
        </para>
        <para>
          The function is defined in <filename>debugstr.h</filename>
          and has the following prototype:
        </para>
        <programlisting>
LPSTR debugres(const void *id);
        </programlisting>
        <para>
          It takes a pointer to the resource id and returns a nicely
          formatted string of the identifier. If the high word of the
          pointer is <literal>0</literal>, then it assumes that the
          identifier is a number and thus returns a string of the
          form:
        </para>
        <programlisting>
#xxxx
        </programlisting>
        <para>
          where <literal>xxxx</literal> are 4 hex-digits representing
          the low word of <parameter>id</parameter>.
        </para>
        <para>
          If the high word of the pointer is not <literal>0</literal>,
          then it assumes that the identifier is a string and thus
          returns a string of the form:
        </para>
        <programlisting>
'&lt;identifier>'
        </programlisting>
        <para>
          Thus, to use it, do something on the following lines:
        </para>
        <programlisting>
#include "debugtools.h"

...

   YYY(xxx, "resource is %s", debugres(myresource));
        </programlisting>
      </sect1>

      <sect1 id="dbg-param">
        <title>The <parameter>--debugmsg</parameter> command line option</title>

        <para>
          So, the <parameter>--debugmsg</parameter> command line
          option has been changed as follows:
        </para>
        <itemizedlist>
          <listitem>
            <para>
              the new syntax is: <parameter>--debugmsg
                [yyy]#xxx[,[yyy1]#xxx1]*</parameter> where
              <literal>#</literal> is either <literal>+</literal> or
              <literal>-</literal>
            </para>
          </listitem>
          <listitem>
            <para>
              when the optional class argument (<literal>yyy</literal>)
              is not present, then the statement will
              enable(<literal>+</literal>)/disable(<literal>-</literal>)
              all messages for the given channel (<literal>xxx</literal>)
              on all classes. For example:
            </para>
            <programlisting>
--debugmsg +reg,-file
            </programlisting>
            <para>
              enables all messages on the <literal>reg</literal>
              channel and disables all messages on the
              <literal>file</literal> channel. This is same as the old
              semantics.
            </para>
          </listitem>
          <listitem>
            <para>
              when the optional class argument (<literal>yyy</literal>)
              is present,  then the statement will enable
              (<literal>+</literal>)/disable(<literal>-</literal>)
              messages for the given channel (<literal>xxx</literal>)
              only on the given class. For example:
            </para>
            <programlisting>
--debugmsg trace+reg,warn-file
            </programlisting>
            <para>
              enables trace messages on the <literal>reg</literal>
              channel and disables warning messages on the
              <literal>file</literal> channel.
            </para>
          </listitem>
          <listitem>
            <para>
              also, the pseudo-channel all is also supported and it
              has the  intuitive semantics:
            </para>
            <screen>
    --debugmsg +all      -- enables all debug messages
    --debugmsg -all      -- disables all debug messages   
    --debugmsg yyy+all   -- enables debug messages for class yyy on all
                           channels.
    --debugmsg yyy-all   -- disables debug messages for class yyy on all
                           channels.
            </screen>
            <para>
              So, for example:
            </para>
            <screen>
    --debugmsg warn-all  -- disables all warning messages.
            </screen>
          </listitem>
        </itemizedlist>

        <para>
          Also, note that at the moment:
        </para>
        <itemizedlist>
          <listitem>
            <para>the <literal>FIXME</literal> and <literal>ERR</literal>
              classes are enabled by default</para>
          </listitem>
          <listitem>
            <para>the <literal>TRACE</literal> and
              <literal>WARN</literal> classes are disabled by
              default</para>
          </listitem>
        </itemizedlist>
      </sect1>

      <sect1 id="dbg-compiling">
        <title>Compiling Out Debugging Messages</title>

        <para>
          To compile out the debugging messages, provide
          <command>configure</command> with the following options:
        </para>
        <screen>
    --disable-debug      -- turns off TRACE, WARN, and FIXME (and DUMP).
    --disable-trace      -- turns off TRACE only.
        </screen>
        <para>
          This will result in an executable that, when stripped, is
          about 15%-20% smaller.  Note, however, that you will not be
          able to effectively debug Wine without these messages.  
        </para>
        <para>
          This feature has not been extensively tested--it may subtly
          break some things.
        </para>
      </sect1>

      <sect1 id="dbg-notes">
        <title>A Few Notes on Style</title>

        <para>
          This new scheme makes certain things more consistent but
          there is still room for improvement by using a common style
          of debug messages. Before I continue, let me note that the
          output format is the following:
        </para>
        <screen>
yyy:xxx:fff &lt;message>

where: 
  yyy = the class (fixme, err, warn, trace)
  xxx = the channel (atom, win, font, etc)
  fff = the function name
        </screen>
        <para>
          these fields are output automatically. All you have to
          provide is the &lt;message> part.
        </para>
        <para>
          So here are some ideas:
        </para>

        <itemizedlist>
          <listitem>
            <para>do NOT include the name of the function: it is included automatically</para>
          </listitem>
          <listitem>
            <para>
              if you want to output the parameters of the function, do
              it as the first thing and include them in parentheses,
              like this: 
              <programlisting>
YYY(xxx, "(%d,%p,etc)...\n", par1, par2, ...);
              </programlisting>
            </para>
          </listitem>
          <listitem>
            <para>
              for stubs, you should output a <literal>FIXME</literal>
              message. I suggest this style:
              <programlisting>
   FIXME(xxx, "(%x,%d...): stub\n", par1, par2, ...);
              </programlisting>
              That is, you output the parameters, then a : and then a string
              containing the word "stub". I've seen "empty stub", and others, but I
              think that just "stub" suffices.
            </para>
          </listitem>
          <listitem>
            <para>
              output 1 and ONLY 1 line per message. That is, the format
              string should contain only 1 <literal>\n</literal> and it
              should always appear at the end of the string. (there are
              many reasons  for this requirement, one of them is that
              each debug macro adds things to the beginning of the line)
            </para>
          </listitem>
          <listitem>
            <para>
              if you want to name a value, use <literal>=</literal> and
              NOT <literal>:</literal>. That is, instead of saying:
              <programlisting>
FIXME(xxx, "(fd: %d, file: %s): stub\n", fd, name);
              </programlisting>
              say:
              <programlisting>
FIXME(xxx, "(fd=%d, file=%s): stub\n", fd, name);
              </programlisting>
              use <literal>:</literal> to separate categories.
            </para>
          </listitem>
          <listitem>
            <para>
              try to avoid the style:
              <programlisting>
FIXME(xxx, "(fd=%d, file=%s)\n", fd, name);
              </programlisting>
              but use:
              <programlisting>
FIXME(xxx, "(fd=%d, file=%s): stub\n", fd, name);
              </programlisting>
              The reason is that if you want to <command>grep</command>
              for things, you would search for <literal>FIXME</literal>
              but in the first case there is no additional information
              available, where in the second one, there is (e.g. the word
              stub)
            </para>
          </listitem>
          <listitem>
            <para>
              if you output a string s that might contain control
              characters, or if <parameter>s</parameter> may be
              <literal>NULL</literal>, use
              <function>debugstr_a</function> (for ASCII strings, or
              <function>debugstr_w</function> for Unicode strings) to
              convert <parameter>s</parameter> to a C string, like  this:
              <programlisting>
HANDLE32 WINAPI YourFunc(LPCSTR s)
{
    FIXME(xxx, "(%s): stub\n", debugstr_a(s)); 
}
              </programlisting>
            </para>
          </listitem>
          <listitem>
            <para>
              if you want to output a resource identifier, use debugres to
              convert it to a string first, like this:
              <programlisting>
HANDLE32 WINAPI YourFunc(LPCSTR res)
{
    FIXME(xxx, "(res=%s): stub\n", debugres(s));
}
              </programlisting>
              if the resource identifier is a <type>SEGPTR</type>, use
              <function>PTR_SEG_TO_LIN</function> to get a
              liner pointer first:
              <programlisting>
HRSRC16 WINAPI FindResource16( HMODULE16 hModule, SEGPTR name, SEGPTR type )
{
[...]
    TRACE(resource, "module=%04x name=%s type=%s\n", 
		 hModule, debugres(PTR_SEG_TO_LIN(name)), 
		 debugres(PTR_SEG_TO_LIN(type)) );
[...]
}
              </programlisting>
            </para>
          </listitem>
          <listitem>
            <para>
              for messages intended for the user (specifically those that
              report errors in <filename>wine.conf</filename>), use the
              <literal>MSG</literal> macro. Use it like a
              <function>printf</function>:
              <programlisting>
MSG( "Definition of drive %d is incorrect!\n", drive ); 
              </programlisting>
              However, note that there are <emphasis>very</emphasis> few
              valid uses of this macro. Most messages are debugging
              messages, so chances are you will not need to use this
              macro. Grep the source to get an idea where it is
              appropriate to use it.
            </para>
          </listitem>
          <listitem>
            <para>
              For structure dumps, use the <function>DUMP</function>
              macro. Use it like a <function>printf</function>, just like
              the <literal>MSG</literal> macro. Similarly, there are only
              a few valid uses of this macro. Grep the source to see when
              to use it.
            </para>
          </listitem>
        </itemizedlist>
      </sect1>

  </chapter>

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