cvs commit: modperl-docs/src/docs/2.0/devel/debug_c debug_c.pod

[st...@apache.org]

stas        2002/06/21 10:26:20

  Modified:    src/docs/2.0/devel/debug_c debug_c.pod
  Log:
  yay, gdb knows to expand C macros now. log notes about this and make's
  macro expansion techniques
  
  Revision  Changes    Path
  1.10      +66 -0     modperl-docs/src/docs/2.0/devel/debug_c/debug_c.pod
  
  Index: debug_c.pod
  ===================================================================
  RCS file: /home/cvs/modperl-docs/src/docs/2.0/devel/debug_c/debug_c.pod,v
  retrieving revision 1.9
  retrieving revision 1.10
  diff -u -r1.9 -r1.10
  --- debug_c.pod	13 Jun 2002 11:14:18 -0000	1.9
  +++ debug_c.pod	21 Jun 2002 17:26:20 -0000	1.10
  @@ -716,6 +716,72 @@
   from reaping it.  So, you could hit the clients/threads limit if you
   segfault a lot.
   
  +=head1 Expanding C Macros
  +
  +Perl, mod_perl and httpd C code makes an extensive use of C macros,
  +which sometimes use many other macros in their definitions, so it
  +becomes quite a task to figure out how to figure out what a certain
  +macro expands to, especially when the macro expands to different
  +values in differnt environments. Luckily there are ways to automate
  +the expansion process.
  +
  +=head2 Expanding C Macros with C<make>
  +
  +The mod_perl I<Makefile>'s include a rule for macro expansions which
  +you can find by looking for the C<c.i.> rule. To expand all macros in
  +a certain C file, you should run C<make filename.c>, which will create
  +I<filename.i> with all macros expanded in it. For example to create
  +I<apr_perlio.i> with all macros used in I<apr_perlio.c>:
  +
  +  % cd modperl-2.0/xs/APR/PerlIO
  +  % make apr_perlio.i
  +
  +the I<apr_perlio.i> file now lists all the macros:
  +
  +  % less apr_perlio.i
  +  # 1 "apr_perlio.c"
  +  # 1 "<built-in>"
  +  #define __VERSION__ "3.1.1 (Mandrake Linux 8.3 3.1.1-0.4mdk)"
  +  ...
  +
  +=head2 Expanding C Macros with C<gdb>
  +
  +With gcc-3.1 or higher and gdb-5.2-dev or higher you can expand macros
  +in gdb, when you step through the code. e.g.:
  +
  +  (gdb) macro expand pTHX_
  +  expands to:  PerlInterpreter *my_perl __attribute__((unused)),
  +  (gdb) macro expand PL_dirty
  +  expands to: (*Perl_Tdirty_ptr(my_perl))
  +
  +For each library that you want to use this feature with you have to
  +compile it with:
  +
  +  CFLAGS="-gdwarf-2 -g3"
  +
  +or whatever is appropriate for your system, refer to the gcc manpage
  +for more info.
  +
  +To compile perl with this debug feature, pass C<-Doptimize='-gdwarf-2
  +-g3'> to C<./Configure>. For Apache run:
  +
  +  CFLAGS="-gdwarf-2 -g3" ./configure [...]
  +
  +for mod_perl you don't have to do anything, as it'll pick the
  +C<$Config{optimize}> Perl flags automatically, if Perl is compiled
  +with C<-DDEBUGGING> (which is implied on most systems, if you use
  +C<-Doptimize='-g'> or similar.)
  +
  +Notice that this will make your libraries B<huge>! e.g. on Linux 2.4
  +Perl 5.8.0's normal I<libperl.so> is about 0.8MB on linux, compiled
  +with C<-Doptimize='-g'> about 2.7MB and with C<-Doptimize='-gdwarf-2
  +-g3'> 12.5MB. C<httpd> is also becomes about 10 times bigger with this
  +feature enabled. I<mod_perl.so> instead of 0.2k becomes 11MB. You get
  +the idea. Of course since you may want this only during the
  +development/debugging, that shouldn't be a problem.
  +
  +The complete details are at:
  +http://sources.redhat.com/gdb/current/onlinedocs/gdb_10.html#SEC69
   
   =head1 Maintainers
   
  
  
  

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