Turn $$ into a magical readonly variable that always fetches getpid() instead of caching it

The intent is that by not caching $$, we eliminate one opportunity for bugs:
If one embeds Perl or uses XS and calls fork(3) from C, Perls notion of $$
may go out of sync with what getpid() returns. By always fetching the
value of $$ via getpid(), this bug opportunity is eliminated. The overhead
of always fetching $$ should be small and is likely only used for tempfile
creation, which should be dwarfed by file system accesses.

1 files changed, 0 insertions, 6 deletions

diff --git a/util.c b/util.c
index bd9010f5ca..f6742e70b4 100644
--- a/util.c
+++ b/util.c
@@ -2759,12 +2759,6 @@ Perl_my_popen(pTHX_ const char *cmd, const char *mode)
       default, binary, low-level mode; see PerlIOBuf_open(). */
    PerlLIO_setmode((*mode == 'r'), O_BINARY);
 #endif 
-
-	if ((tmpgv = gv_fetchpvs("$", GV_ADD|GV_NOTQUAL, SVt_PV))) {
-	    SvREADONLY_off(GvSV(tmpgv));
-	    sv_setiv(GvSV(tmpgv), PerlProc_getpid());
-	    SvREADONLY_on(GvSV(tmpgv));
-	}
 #ifdef THREADS_HAVE_PIDS
 	PL_ppid = (IV)getppid();
 #endif