IRIX Base Documentation 2001 May/SGI IRIX Base Documentation 2001 May.iso/usr/share/catman/p_man/cat3/perl5/diagnostics.z/diagnostics

Text File | 1998-10-30 | 7.7 KB | 265 lines

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     diagnostics - Perl compiler pragma to force verbose warning diagnostics

     splain - standalone program to do the same thing

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     As a pragma:

         use diagnostics;
         use diagnostics -verbose;

         enable  diagnostics;
         disable diagnostics;

     Aa a program:

         perl program 2>diag.out
         splain [-v] [-p] diag.out


DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     TTTThhhheeee ddddiiiiaaaaggggnnnnoooossssttttiiiiccccssss Pragma

     This module extends the terse diagnostics normally emitted by both the
     perl compiler and the perl interpeter, augmenting them with the more
     explicative and endearing descriptions found in the _p_e_r_l_d_i_a_g manpage.
     Like the other pragmata, it affects the compilation phase of your program
     rather than merely the execution phase.

     To use in your program as a pragma, merely invoke

         use diagnostics;

     at the start (or near the start) of your program.  (Note that this _d_o_e_s
     enable perl's ----wwww flag.)  Your whole compilation will then be _s_u_b_j_e_c_t(ed
     :-) to the enhanced diagnostics.  These still go out SSSSTTTTDDDDEEEERRRRRRRR.

     Due to the interaction between runtime and compiletime issues, and
     because it's probably not a very good idea anyway, you may not use no
     diagnostics to turn them off at compiletime.  However, you may control
     there behaviour at runtime using the _d_i_s_a_b_l_e() and _e_n_a_b_l_e() methods to
     turn them off and on respectively.

     The ----vvvveeeerrrrbbbboooosssseeee flag first prints out the the _p_e_r_l_d_i_a_g manpage introduction
     before any other diagnostics.  The $diagnostics::PRETTY variable can
     generate nicer escape sequences for pagers.

     TTTThhhheeee _s_p_l_a_i_n Program

     While apparently a whole nuther program, _s_p_l_a_i_n is actually nothing more
     than a link to the (executable) _d_i_a_g_n_o_s_t_i_c_s._p_m module, as well as a link
     to the _d_i_a_g_n_o_s_t_i_c_s._p_o_d documentation.  The ----vvvv flag is like the use



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ddddiiiiaaaaggggnnnnoooossssttttiiiiccccssss((((3333))))                                                  ddddiiiiaaaaggggnnnnoooossssttttiiiiccccssss((((3333))))



     diagnostics -verbose directive.  The ----pppp flag is like the
     $diagnostics::PRETTY variable.  Since you're post-processing with _s_p_l_a_i_n,
     there's no sense in being able to _e_n_a_b_l_e() or _d_i_s_a_b_l_e() processing.

     Output from _s_p_l_a_i_n is directed to SSSSTTTTDDDDOOOOUUUUTTTT, unlike the pragma.

EEEEXXXXAAAAMMMMPPPPLLLLEEEESSSS
     The following file is certain to trigger a few errors at both runtime and
     compiletime:

         use diagnostics;
         print NOWHERE "nothing\n";
         print STDERR "\n\tThis message should be unadorned.\n";
         warn "\tThis is a user warning";
         print "\nDIAGNOSTIC TESTER: Please enter a <CR> here: ";
         my $a, $b = scalar <STDIN>;
         print "\n";
         print $x/$y;

     If you prefer to run your program first and look at its problem
     afterwards, do this:

         perl -w test.pl 2>test.out
         ./splain < test.out

     Note that this is not in general possible in shells of more dubious
     heritage, as the theoretical

         (perl -w test.pl >/dev/tty) >& test.out
         ./splain < test.out

     Because you just moved the existing ssssttttddddoooouuuutttt to somewhere else.

     If you don't want to modify your source code, but still have on-the-fly
     warnings, do this:

         exec 3>&1; perl -w test.pl 2>&1 1>&3 3>&- | splain 1>&2 3>&-

     Nifty, eh?

     If you want to control warnings on the fly, do something like this.  Make
     sure you do the use first, or you won't be able to get at the _e_n_a_b_l_e() or
     _d_i_s_a_b_l_e() methods.

         use diagnostics; # checks entire compilation phase
             print "\ntime for 1st bogus diags: SQUAWKINGS\n";
             print BOGUS1 'nada';
             print "done with 1st bogus\n";







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ddddiiiiaaaaggggnnnnoooossssttttiiiiccccssss((((3333))))                                                  ddddiiiiaaaaggggnnnnoooossssttttiiiiccccssss((((3333))))



         disable diagnostics; # only turns off runtime warnings
             print "\ntime for 2nd bogus: (squelched)\n";
             print BOGUS2 'nada';
             print "done with 2nd bogus\n";

         enable diagnostics; # turns back on runtime warnings
             print "\ntime for 3rd bogus: SQUAWKINGS\n";
             print BOGUS3 'nada';
             print "done with 3rd bogus\n";

         disable diagnostics;
             print "\ntime for 4th bogus: (squelched)\n";
             print BOGUS4 'nada';
             print "done with 4th bogus\n";


IIIINNNNTTTTEEEERRRRNNNNAAAALLLLSSSS
     Diagnostic messages derive from the _p_e_r_l_d_i_a_g._p_o_d file when available at
     runtime.  Otherwise, they may be embedded in the file itself when the
     splain package is built.   See the _M_a_k_e_f_i_l_e for details.

     If an extant $SIG{__WARN__} handler is discovered, it will continue to be
     honored, but only after the _d_i_a_g_n_o_s_t_i_c_s::_s_p_l_a_i_n_t_h_i_s() function (the
     module's $SIG{__WARN__} interceptor) has had its way with your warnings.

     There is a $diagnostics::DEBUG variable you may set if you're desperately
     curious what sorts of things are being intercepted.

         BEGIN { $diagnostics::DEBUG = 1 }


BBBBUUUUGGGGSSSS
     Not being able to say "no diagnostics" is annoying, but may not be
     insurmountable.

     The -pretty directive is called too late to affect matters.  You have to
     do this instead, and _b_e_f_o_r_e you load the module.

         BEGIN { $diagnostics::PRETTY = 1 }

     I could start up faster by delaying compilation until it should be
     needed, but this gets a "panic: top_level" when using the pragma form in
     Perl 5.001e.

     While it's true that this documentation is somewhat subserious, if you
     use a program named _s_p_l_a_i_n, you should expect a bit of whimsy.

AAAAUUUUTTTTHHHHOOOORRRR
     Tom Christiansen <_t_c_h_r_i_s_t@_m_o_x._p_e_r_l._c_o_m>, 25 June 1995.






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