Change 13029 by jhi@alpha on 2001/11/15 21:35:36
Advise against -P as instructed by Schwern.
Affected files ...
.... //depot/perl/pod/perlrun.pod#45 edit
Differences ...
==== //depot/perl/pod/perlrun.pod#45 (text) ====
Index: perl/pod/perlrun.pod
--- perl/pod/perlrun.pod.~1~ Thu Nov 15 14:45:05 2001
+++ perl/pod/perlrun.pod Thu Nov 15 14:45:05 2001
@@ -569,12 +569,39 @@
=item B<-P>
-causes your program to be run through the C preprocessor before
+B<NOTE: Use of -P is strongly discouraged because of its inherent
+problems, including poor portability.>
+
+This option causes your program to be run through the C preprocessor before
compilation by Perl. Because both comments and B<cpp> directives begin
with the # character, you should avoid starting comments with any words
recognized by the C preprocessor such as C<"if">, C<"else">, or C<"define">.
-Also, in some platforms the C preprocessor knows too much: it knows
-about the C++ -style until-end-of-line comments starting with C<"//">.
+
+If you're considering using C<-P>, you might also want to look at the
+Filter::cpp module from CPAN.
+
+The problems of -P include, but are not limited to:
+
+=over 10
+
+=item *
+
+The C<#!> line is stripped, so any switches there don't apply.
+
+=item *
+
+A C<-P> on a C<#!> line doesn't work.
+
+=item *
+
+B<All> lines that begin with (whitespace and) a C<#> but
+do not look like cpp commands, are stripped, including anything
+inside Perl strings, regular expressions, and here-docs .
+
+=item *
+
+In some platforms the C preprocessor knows too much: it knows about
+the C++ -style until-end-of-line comments starting with C<"//">.
This will cause problems with common Perl constructs like
s/foo//;
@@ -588,8 +615,22 @@
s!foo!!;
-If you're considering using C<-P>, you might also want to look at the
-Filter::cpp module from CPAN.
+
+
+=item *
+
+It requires not only a working C preprocessor but also a working
+F<sed>. If not on UNIX, you are probably out of luck on this.
+
+=item *
+
+Script line numbers are not preserved.
+
+=item *
+
+The C<-x> does not work with C<-P>.
+
+=back
=item B<-s>
End of Patch.
