Make description of new warning introduced in change 26780 more precise

[p5sagit/p5-mst-13.2.git] / pod / perlembed.pod

diff --git a/pod/perlembed.pod b/pod/perlembed.pod
index 05feccd..0bd569f 100644 (file)
--- a/pod/perlembed.pod
+++ b/pod/perlembed.pod
@@ -506,7 +506,16 @@ been wrapped here):
      PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
 
      text = NEWSV(1099,0);
-     sv_setpv(text, "When he is at a convenience store and the bill comes to some amount like 76 cents, Maynard is aware that there is something he *should* do, something that will enable him to get back a quarter, but he has no idea *what*.  He fumbles through his red squeezey changepurse and gives the boy three extra pennies with his dollar, hoping that he might luck into the correct amount.  The boy gives him back two of his own pennies and then the big shiny quarter that is his prize. -RICHH");
+     sv_setpv(text, "When he is at a convenience store and the "
+       "bill comes to some amount like 76 cents, Maynard is "
+       "aware that there is something he *should* do, something "
+       "that will enable him to get back a quarter, but he has "
+       "no idea *what*.  He fumbles through his red squeezey "
+       "changepurse and gives the boy three extra pennies with "
+       "his dollar, hoping that he might luck into the correct "
+       "amount.  The boy gives him back two of his own pennies "
+       "and then the big shiny quarter that is his prize. "
+       "-RICHH");
 
      if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/
        printf("match: Text contains the word 'quarter'.\n\n");
@@ -784,6 +793,7 @@ with L<perlfunc/my> whenever possible.
      }
      perl_construct(my_perl);
 
+     PL_origalen = 1; /* don't let $0 assignment update the proctitle or embedding[0] */
      exitstatus = perl_parse(my_perl, NULL, 2, embedding, NULL);
      PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
      if(!exitstatus) {
@@ -843,6 +853,21 @@ perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END>
 to get the new behaviour. This also enables the running of END blocks if
 the perl_parse fails and C<perl_destruct> will return the exit value.
 
+=head2 $0 assignments
+
+When a perl script assigns a value to $0 then the perl runtime will
+try to make this value show up as the program name reported by "ps" by
+updating the memory pointed to by the argv passed to perl_parse() and
+also calling API functions like setproctitle() where available.  This
+behaviour might not be appropriate when embedding perl and can be
+disabled by assigning the value C<1> to the variable C<PL_origalen>
+before perl_parse() is called.
+
+The F<persistent.c> example above is for instance likely to segfault
+when $0 is assigned to if the C<PL_origalen = 1;> assignment is
+removed.  This because perl will try to write to the read only memory
+of the C<embedding[]> strings.
+
 =head2 Maintaining multiple interpreter instances
 
 Some rare applications will need to create more than one interpreter
@@ -1109,8 +1134,6 @@ Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl
 have used this model for Oracle, Netscape and Internet Information
 Server Perl plugins.
 
-July 22, 1998
-
 =head1 COPYRIGHT
 
 Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant.  All