From: Gisle Aas <gisle@activestate.com>
Date: Wed, 11 Jan 2006 09:52:18 +0000 (+0000)
Subject: Make setting 'PL_origalen = 1' before perl_parse() disable
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=a2722ac963c473daf784eb7bed19dab587ac5fe6;p=p5sagit%2Fp5-mst-13.2.git

Make setting 'PL_origalen = 1' before perl_parse() disable
argv[0] munging when $0 is assigned to.

p4raw-id: //depot/perl@26779
---

diff --git a/mg.c b/mg.c
index 3e3ebfd..87cea48 100644
--- a/mg.c
+++ b/mg.c
@@ -2540,7 +2540,7 @@ Perl_magic_set(pTHX_ SV *sv, MAGIC *mg)
 	/* The BSDs don't show the argv[] in ps(1) output, they
 	 * show a string from the process struct and provide
 	 * the setproctitle() routine to manipulate that. */
-	{
+	if (PL_origalen != 1) {
 	    s = SvPV_const(sv, len);
 #   if __FreeBSD_version > 410001
 	    /* The leading "-" removes the "perl: " prefix,
@@ -2561,7 +2561,7 @@ Perl_magic_set(pTHX_ SV *sv, MAGIC *mg)
 	}
 #endif
 #if defined(__hpux) && defined(PSTAT_SETCMD)
-	{
+	if (PL_origalen != 1) {
 	     union pstun un;
 	     s = SvPV_const(sv, len);
 	     un.pst_command = (char *)s;
diff --git a/perl.c b/perl.c
index b1671d9..2958599 100644
--- a/perl.c
+++ b/perl.c
@@ -1439,7 +1439,10 @@ setuid perl scripts securely.\n");
     PL_origargc = argc;
     PL_origargv = argv;
 
-    {
+    if (PL_origalen != 0) {
+	PL_origalen = 1; /* don't use old PL_origalen if perl_parse() is called again */
+    }
+    else {
 	/* Set PL_origalen be the sum of the contiguous argv[]
 	 * elements plus the size of the env in case that it is
 	 * contiguous with the argv[].  This is used in mg.c:Perl_magic_set()
diff --git a/pod/perlembed.pod b/pod/perlembed.pod
index 38211e5..0bd569f 100644
--- a/pod/perlembed.pod
+++ b/pod/perlembed.pod
@@ -793,6 +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) {
@@ -852,6 +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